Browse Forums Eco Living 1 Jun 17, 2015 3:46 pm We're about to get two 15,000L stainless steel rainwater tanks. We'll use the water for drinking/cooking, watering plants and flushing the toilet via a pump (external). We want to avoid drinking water with sludge in and to find the cheapest way of desludging. We are thinking of having a gate valve right at the bottom of the tanks, to use to water the garden via a hose and to let out muddy water to desludge the tank occasionally. We plan to have another 2 outlets about 2 or 3 feet up to go to the pump and also to a bucket tap. We've looked at a Water Boy and Tank Vac for minimising sludge problems, and our proposal is cheaper, but we're not sure how effective it would be. Does anyonehave any experience that could throw some light on this? We also plan to have a rain head to divert leaves and a first flush diverter. We get a lot of dust as we live near a gravel road, in Castlemaine (which used to get about 20" of rain a year before the climate started drying). We were thinking that if we wanted to let out all the sludge via the bottom outlet, we could do it when the tank was nearly empty, and poke a hose or stick through the outlet to stir up and dislodge the sludge. Any comments would be appreciated. Re: Sludge in rain water tank 2Jun 18, 2015 9:43 am Any sort of first flush diverter or sediment trap before the water enters the tanks will remove most stuff that will turn into sludge as you have already said. The Tank Vac is supposed to be pretty good from what I've heard. You also want to make sure that the water you are drawing off from your tank ( especially seeing you are using it for drinking ) is not coming from the anaerobic zone so I presume that is why you have one of the outlets 3 ft from the bottom of the tank. Forum member SaveH2O is the rainwater guru on these forums so hopefully he'll chime in with some good advice. How much are those S/Steel tanks costing you if you don't mind me asking ? Stewie Re: Sludge in rain water tank 3Jun 22, 2015 3:22 pm Sorry for the delay, I have a huge work demand at the moment. The principle of best practice is simple;... Prevention is better than cure. You need to deliver the best quality water possible to the tank and then deliver the best quality water in the tank to the pump. A well set up system will have minimal sludge and what sediment does go to the tank will be much different to the normal muck you find in most tanks. Having two tanks gives you an immediate advantage as it allows you to have a settling tank system. This simply means that for your situation, you divert water to one tank and decanted water is later diverted to the second tank that the pump draws from. It is also best not to have the pump draw outlet fitted close to the bottom of the tank (the anaerobic zone) unless you have a floating inlet like a Waterboy fitted...which I recommend. A floating inlet draws the best quality water from 200mm below the water surface and having the inlet 200mm below the surface prevents the pump drawing a free surface vortex that could easily ingest air into the pump. http://www.crystalclearwater.com.au/waterboy/ Having a floating inlet connected to the settling tank's balance pipe outlet is also a good idea as the transferred water will be drawn from the very best water in the settling tank. Wet system downpipes should also have leaf diverters fitted to the downpipes to prevent organic matter entering the pipes and to prevent mosquitoes breeding. They are a mandatory fitting to wet system downpipes in many areas of Australia but not where you are. While I recommend fitting leaf diverters to wet system downpipes, I cannot endorse any of the current ones available. I am however prototyping a compact leaf diverter that will use a new highly efficient non mesh filter screen that I have designed but it won't be available until the end of the year at the earliest at this stage. As well as having higher yield and requiring less maintenance, the filtration will probably be 600 micron as opposed to the common 955 micron wire mesh commonly used in most others. It is also easy to install a cheap and simple DIY sediment trap into the wet system's pipe work. The trap is installed 4-5 metres past an elbow or tee as it must be in a non turbulent section of pipe to capture settled bed load. As you can see in the diagram below, when the very slow travelling bed load reaches the opening in the 45 degree junction, it simply drops down and is later flushed through a reduced sized pipe at high velocity. Note that the inspection fitting is not needed if leaf diverters are fitted. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Having mosquito proof leaf diverters also allows you to fit a low restriction inlet. This branches a smaller pipe off a tee at the bottom of the vertical riser that normally delivers water from a wet system to a tank's top meshed inlet. The smaller pipe connects to an inlet valve fitted 100mm - 200mm above the bottom of the tank via a flexible coupling. The low restriction flow path effectively flushes the wet system pipe of fine sediment after most rain events. Because a low restriction inlet operates with greater head pressure (the height difference between the leaf diverter and the level of water in the tank) than the vertical riser that rises above the tank, the low restriction inlet has priority flow, meaning that the vertical riser's usually low head is supplemented by the low restriction inlet's flow rate during heavy rain. Other benefits include having the anaerobic zone oxygenated with oxygen rich water as well as the level of water retained in the wet system being less...level with the water level in the tank rather than level with the top of the riser pipe. Water is also saved because of there no longer being a need to flush the wet system pipes to clear crud and prevent stagnation. You can read about the low restriction inlet in the post linked below. viewtopic.php?p=1211691#p1211691 You also need to calculate the amount of water that will be delivered to the tank during a 1:20 ARI as this determines what the tank's overflow capacity needs to be. Note that overflow calculations MUST factor the flow restricting meshed outlet. The TankVac serves 2 purposes...it vacuums the tank's floor via a network of holed pipes every time it overflows but it also provides a greatly increased tank overflow capacity of about 540 litres per minute. I have seen numerous tanks installed by so called 'professionals' where the tank's overflow has been hopelessly inadequate to cope with the tank's inflow capacity during a storm, in fact, very few 'professional' installers will be able to tell you what a tank's overflow capacity is if asked. https://www.youtube.com/watch?v=e1_B9WITe94 If you don't use a TankVac, it would still take many years before you would even consider syphoning the bottom of the tank if you use best practice. There are tank cleaning companies around but you are better of spending the bit extra in the first place by getting a TankVac if the required discharge calculations specify and having the multi continuous benefits. A note about standard wet systems and the sediment layer. Water falling through a tank's top meshed inlet can cause significant sediment resuspension during heavy rain. It is ironic that standard rainwater harvesting systems deliver water to the top of the tank and the pump draws water from the bottom of the tank, the exact opposite of best practice. You could also consider fitting some cartridge filters as a final precaution but they would have an easy life. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Sludge in rain water tank 4Jun 22, 2015 4:55 pm Another thought would be to have something like a 1000L tank with a low inlet (http://www.anewhouse.com.au/2012/11/rai ... rovements/) and high outlet to the first of your 15000L tanks. Any sludge would tend to be collected in this 1st tank which would be easier to desludge than a large tank. Alternatively are you required to have a bushfire reserve volume? as this volume can be used to settle out any particles. Last time I looked the volume for Victoria was 10,000L but more could be needed (see http://www.anewhouse.com.au/2014/03/bus ... ve-volume/) The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Sludge in rain water tank 5Jun 22, 2015 7:31 pm bashworth Another thought would be to have something like a 1000L tank with a low inlet (http://www.anewhouse.com.au/2012/11/rai ... rovements/) and high outlet to the first of your 15000L tanks. Any sludge would tend to be collected in this 1st tank which would be easier to desludge than a large tank. Hi Brian, Do you mean like the photo below? The small flush tank in the photo wasn't correctly done as it wasn't fitted with a low inlet, probably to prevent a venturi effect from recycling the water but if the small tank was sited further away from the vertical riser and the pipe between the vertical riser and the flush tank was reduced in size, then yes, it is a very good method. Eliminating the standard first flush diverters along with their drippers saves money and water plus the flush can be used elsewhere. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Sludge in rain water tank 6Jun 22, 2015 8:01 pm SaveH2O The small flush tank in the photo wasn't correctly done as it wasn't fitted with a low inlet, probably to prevent a venturi effect from recycling the water but if the small tank was sited further away from the vertical riser and the pipe between the vertical riser and the flush tank was reduced in size, then yes, it is a very good method. Eliminating the standard first flush diverters along with their drippers saves money and water plus the flush can be used elsewhere. Yes we are on the same page. The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Sludge in rain water tank 7Jul 01, 2015 1:42 pm Thanks very much for all the helpful comments. Thanks for making the time when you were busy, Save H2O. Stewie , the tanks will be 2.35m high. Do you know where the aerobic zone would start/end when they’re full? I don’t know whether it is the top few inches, or the top half, or even the top three quarters. Does it depend on how much movement is in the tank (ie water going in and out)? Would the outlet at 3' be high enough to get good quality water? The tanks will be about $3,500 each plus $50 extra for each outlet after the first one (from designertanks.com.au). Save H2O, what problem do the leaf diverting rainheads currently available have? We’re hoping to get the tanks installed in 3 or 4 weeks, so that will be too soon to try the one you’re working on now. You said you recommend fitting leaf diverters to wet system downpipes. Do you mean that you don’t recommend them for “dry” systems, which don’t go underground? At the moment we just have pops in the bottom of the gutter, and they get blocked up with gum leaves, pine needles and small twigs/stems. I’ll also be planting some casuarinas, and the branchlets from them are likely to get on the roof. I presume ours will be a “dry” system, as the water from the roof will go straight into the tanks without going underground. However there is an underground pipe to connect the 2 tanks and also to connect to the pump. Would your suggestions for a “wet” system apply to our system? We were thinking of having the 2 tanks and fittings pretty much symmetrical, although one will be slightly higher than the other. Would that be OK with your settling tank suggestion? I will have to study it further to understand it better. Bashworth, we don’t have to have reserve water for fighting bushfires. There’s a fire hydrant several hundred metres away, and a CFA firefighter I know told me the CFA can pump water from the top inlet of rainwater tanks if necessary. Re your idea of a 1000L tank, we did think of storing excess dirty water from the first flush diverter in a 44 gal drum, to use on a vegie garden, but I realise that’s different from your suggestion, which I presume could replace a first flush diverter. Despite the wealth of information you’ve all given, I’m still wondering: would an outlet at the bottom with a gate valve be able to be used to desludge each tank adequately with our system as proposed, with first flush diverter hopefully preventing most of the sludge getting into the tank? The Tank Vac and Water Boy sound good, but we’ve nearly got the new house finished and have almost run out of money, so rather than do a perfect system with whatever it costs, we’re now trying to get as good a system as we can spending as little extra as possible. We’re also looking at a system to manually override the FFD, as we often get frequent very small rains in winter, when the roof is pretty clean, but in summer, the gravel road nearby gets very dry and dusty, and thick dust blows onto the roof, and we sometimes don’t get rain for months, so we may need to flush heaps of dirt out during the first autumn rain, and flush hardly any out during winter. Re: Sludge in rain water tank 9Jul 01, 2015 10:31 pm A gate valve at the bottom of a large tank will not be very effective at desludging. What happens is that the valve takes water from above in preference to water at the same level so the sludge is normally only removed from less than 1m from the outlet. (this is known as 'rat tailing' ) In water treatment the normal way to avoid this occurring is to have a steep conical base on large clarifier tanks or have paddles that 'sweep' the sludge to a central well. The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Sludge in rain water tank 10Jul 01, 2015 10:44 pm Quote: It might help if I post a drawing of our set up. Can anyone tell me how to do this (with a drawing done in Word)? The drawing should be saved in an image format like jpeg, png, gif etc or just take a screenshot of it which will save it as one of the above. 1) Upload your photos to an image hosting site like Photobucket. 2) Click on your photo that you want to post here. 3) Locate the IMG tag under "Share Links" on the right hand side of the photo. 4) Click on that IMG code line and copy it. 5) Paste that into your post here then hit the submit button. Here's a photo from a pdf I downloaded a while back when I started down the rainwater tank path... I sure know a lot more about them after joining this forum and digesting the info provided by guys like SaveH2O and Bashworth. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Stewie Re: Sludge in rain water tank 11Jul 06, 2015 11:41 pm einadia Do you know where the aerobic zone would start/end when they’re full? The anaerobic zone is generally considered to be the bottom 300mm but the very worse water will be in the bottom 50-60mm or so. It must be remembered though that most tanks build up a sizable sediment layer within a few years and generalisations apply to the average system. If you have a good system that delivers good quality water to the tank, the sediment layer and resultant anaerobic zone will be much less. You will also have a different type of sediment if you have a good system. Instead of having foul muck and tar like crud that glues itself to the bottom of the tank, the 'sediment' will be similar to talcum powder and it won't stick. No more having to use high pressure hoses to clean the tank! einadia Would the outlet at 3' be high enough to get good quality water? When you order its size and height, bear in mind that if you say you want it 3" (76mm) above the bottom of the tank, the supplier will take that measurement as being the mid point, not the outlet's lowest point. Many tanks are fitted with the outlet valve 50mm or less above the bottom of the tank at the valves lowest point. I recommend to my customers (with good systems) that the outlet should be a minimum 80mm above the bottom of the tank at the outlets lowest point unless they use a floating inlet like the WaterBoy. An irrigation shop can usually make a floating inlet for about $60, just make sure that the inlet is 200mm below the surface to avoid drawing a free surface vortex. Tests have shown that 60mm is ok in our systems but we also divert wet system water into the tank via a low restriction inlet and this also oxygenates the anaerobic zone. Anaerobic means deprived of oxygen. You will notice in the diagram stewie posted that the dry system infeed pipe is diverted to the bottom of the tank. This method uses a calming inlet (see photo below) that prevents sediment re-suspension from falling water plus the diverted oxygen rich water oxygenates the anaerobic zone. The worst position for a tank's dry system top meshed inlet is above the tank's outlet valve that supplies the pump. einadia Save H2O, what problem do the leaf diverting rainheads currently available have? Manufacturers use mosquito proof wire mesh (apertures that are less than 1,000 micron). Many early downpipe leaf diverters used a coarse (6mm-10mm) outer mesh and an inner mosquito proof wire meshed screen. Solid bird droppings and other large material passed through the coarse mesh and then either washed through the finer mesh or clogged the fine apertures. Because most fine grit and other muck is flushed off the roof and from the gutters during heavy rain, the chances were greater that the finer mesh would block at these times. When this happened, there were overflows. It is also dangerous to be climbing a ladder in the wet to remove and clean blocked wire mesh screens. The trend now is to have a single outer mosquito proof wire mesh screen but leaves stick to wire mesh unless the mesh is at a minimum 60 degree angle. Most are at 40-45 degrees and leaves sticking to the mesh results in a lot of splash and yield loss. So why not increase the angle? Well, this would necessitate a substantial height increase and many property owners with large tanks need every mm of head they have available to generate flow through wet systems. A larger unit would also use more material and increase packaging and transport costs. There is also another more technical reason. The wire mesh used has a low % of open area and a lot of water can roll down wire mesh on a steep angle because the cohesive force of the water flowing down the fine mesh can be greater than the gravitational forces trying to pull the water through small apertures. Additionally, when a downpipe is diverted under the eave and then vertically to a leaf diverter, most of the water transfers from the horizontal eave section of downpipe to the downpipe's front vertical wall by surface adhesion, resulting in a lot of water falling near the diverter's front edge. If this small area is blocked or there are any leaves, a lot of water will overflow. einadia You said you recommend fitting leaf diverters to wet system downpipes. Do you mean that you don’t recommend them for “dry” systems, which don’t go underground? At the moment we just have pops in the bottom of the gutter, and they get blocked up with gum leaves, pine needles and small twigs/stems. I’ll also be planting some casuarinas, and the branchlets from them are likely to get on the roof. If you have a leaf problem, you should be fixing the problem because fitting leaf diverters would present their own additional problems as described. I won't manufacture my unit unless it has fine filtration, high yield and it effectively sheds leaves and other rubbish. I cannot recommend any gutter guard but I can highly recommend the Leaf Safe Guttering system. http://www.leafsafeguttering.com.au/ einadia I presume ours will be a “dry” system, as the water from the roof will go straight into the tanks without going underground. However there is an underground pipe to connect the 2 tanks and also to connect to the pump. Would your suggestions for a “wet” system apply to our system? I can't see your house but it would be very unusual for a house that is reliant on harvested rainwater for potable use to harvest every downpipe and not have a wet system. Also, what about sheds, carport or garage. It also sounds like the pump will draw water from both tanks, as such, you will not have a settling tank system. I would need to see a diagram to comment further apart from stating that it is never a good idea to have a sump in a transfer line as per your intended balance line. einadia We were thinking of having the 2 tanks and fittings pretty much symmetrical, although one will be slightly higher than the other. Would that be OK with your settling tank suggestion? I will have to study it further to understand it better. No problems. You would obviously divert into the higher tank and draw water from the lower one. For the cleanest water, connect a WaterBoy to the balance pipe outlet on the first tank. The second tank will not have a sediment layer. Just be aware that if you also have a lower balance line, the higher tank will never fill to its fullest capacity. Many tanks are also poorly optioned with the top meshed inlet well away from the overflow outlet. The overflow outlet's wire mesh can gum up and when this happens, the tank will over-top. You need to be able to access the overflow mesh whenever necessary. einadia Re your idea of a 1000L tank, we did think of storing excess dirty water from the first flush diverter in a 44 gal drum, to use on a vegie garden, but I realise that’s different from your suggestion, which I presume could replace a first flush diverter. It would replace all of the first flush diverters but you cannot have a low restriction inlet fitted to the first tank (if you have a wet system) because the system would remain flooded if you did. You can only use a vertical riser. If you didn't want to divert first flush at any time, you would simply close the flush tank's inlet valve. The size of the tank would also depend on your roof area and the usage envisaged for the diverted flush. If you have a dry system, then you would need to work out the length of pipes you would require, the pipes capacity and cost. I have never seen a single flush tank used with a dry system. einadia I’m still wondering: would an outlet at the bottom with a gate valve be able to be used to desludge each tank adequately with our system as proposed, with first flush diverter hopefully preventing most of the sludge getting into the tank? First flush diverters don't prevent sediment going into the tank despite what the ads may tell you. Most muck is washed from the roof and gutters during heavy rain, long after the first flush diverter fills. I also agree with bashworth's answer re rat tailing. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Sludge in rain water tank 12Jul 09, 2015 4:11 pm Thanks very much for the detailed reply, Save H2O. I'm still struggling to get a drawing done and posted, so I'll try to describe our system in words: The roof is fairly flat, is in one plane and slopes to the south, where there is the roof's only gutter (a half round one). It has a slight peak in the middle, and at each end of the gutter will be a 15,000L tank. At the moment we are planning to have a leaf diverting rainhead and a first flush diverter on each tank, and to add some valves and an extra pipe to the first flush diverter so that we can manually override it and flush more when the roof is very dusty and less when it rains often and the roof is fairly clean. The plumbers have already put in an underground pipe which will link the two tanks, and will go to a pump in the middle, with which we will be able to pump water to the kitchen and toilet when the pressure is too low for gravity feed. We plan to put a valve at each outlet to the pump so we can separate the two tanks. The difference in level between the two tanks is 290mm. We're thinking of putting an outlet right at the bottom of each, to water the garden and hopefully to remove some sludge and dirty water, and a bucket tap at about 600-900mm (not 3"), and to also have the outlet to go into the house at about 600-900mm. We thought the outlet at the bottom would be a cheaper way of desludging than using a Tank Vac, but aren't sure how effective it would be. Re: Sludge in rain water tank 13Jul 09, 2015 11:56 pm einadia and at each end of the gutter will be a 15,000L tank. You won't have a settling tank system then. einadia The plumbers have already put in an underground pipe which will link the two tanks, and will go to a pump in the middle, with which we will be able to pump water to the kitchen and toilet when the pressure is too low for gravity feed. The difference in level between the two tanks is 290mm. In this scenario, the outlet valve height is critical and the best solution is to have floating inlets. If the bottom of one tank sits lower than the other, then you will need to talk to the plumber about having a check valve fitted to the lower pipe to safeguard against the possibility of the higher pipe partially draining when the lower tank's level is low but note that a check valve would also prevent the pipe from operating as a transfer pipe. I personally would draw from the lower tank and have a separate balance line between the tanks. einadia We're thinking of putting an outlet right at the bottom of each, to water the garden and hopefully to remove some sludge and dirty water, and a bucket tap at about 600-900mm (not 3"), and to also have the outlet to go into the house at about 600-900mm. A garden outlet at the bottom of the tank will only draw the sediment from its immediate vicinity and will have no influence over the tank's greater floor area as explained by bashworth. You could have some capped drilled pipes made up (in a 'fan' pattern) and attached to the outlet on the inside of the tank. These would have the same effect as the network of drilled pipes that supply the tank vac, the big difference being that while the TankVac drains at about 540 litres per minute, your pipes would only need to supply less than 4% of this volume. The number and size of holes needed would have to be calculated accordingly but there won't be many and of course only a small section of floor in front of the outlet would be treated due to the limitation on the number of holes in the pipes if they are to be effective. An outlet at 600=900mm would mean that you will have a lot of inaccessible water plus a floating inlet would still access better quality water. I rig up a 25mm uPVC pressure pipe with a tee at the bottom fitted with two drilled and capped short 25mm pipes and just vacuum the bottom of the tanks when one needs to be done. I have heard of people using pool cleaners but I have never seen it done and the tank's top meshed inlet size also limits the size of any object that can be passed through its opening. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Sludge in rain water tank 14Jul 11, 2015 1:20 pm Some more questions, H2O, and anyone else who’d like to contribute: What is better about oxygenated water? “the sediment layer and resultant anaerobic zone”: I’m wondering how the anaerobic layer results from sediment - do the bacteria in the sediment take oxygen from the water to break down any organic matter in the sediment, perhaps? What causes the difference you mentioned in the types of sediment, Save H2O – the foul sticky stuff and the powdery stuff? “An irrigation shop can usually make a floating inlet for about $60, just make sure that the inlet is 200mm below the surface to avoid drawing a free surface vortex.” I spoke to the bloke at a local irrigation supply place this morning about a floating inlet, and he tried to talk me out of it, saying that with moving parts, something's bound to go wrong eventually - a crack at the tank outlet, letting sludge into the outlet, and/or deterioration of the flexible pipe that goes up and down and/or providing an extra surface for sludge, algae, bacteria, etc to stick to. What could the pipe be made of (the one that goes up and down with the water level)? My understanding is that PVC is made flexible by adding plasticisers with phthalates (which are endocrine disrupters - pseudo oestrogens) in, and water from PVC hoses smells bad and tastes absolutely disgusting. Could it be made of a less flexible plastic like polyethylene in a spiral? “we also divert wet system water into the tank via a low restriction inlet and this also oxygenates the anaerobic zone.” I’m having trouble visualising this and working out if it would apply to our system. “it is never a good idea to have a sump in a transfer line as per your intended balance line.” What problems do you anticipate, Save H2O? By "balance line", do you mean the pipe that can fill one tank from the other? “Many tanks are also poorly optioned with the top meshed inlet well away from the overflow outlet. The overflow outlet's wire mesh can gum up and when this happens, the tank will over-top.” Do you mean it’s best to have the overflow close to the inlet? Thanks again for all your information. I still have to go through some of it more thoroughly, and will probably have more questions. Re: Sludge in rain water tank 15Jul 11, 2015 6:36 pm einadia What is better about oxygenated water? It is fresher, healthier and tastes better. There is plenty of information on the net. einadia do the bacteria in the sediment take oxygen from the water to break down any organic matter in the sediment, perhaps? Yes. einadia What causes the difference you mentioned in the types of sediment, Save H2O – the foul sticky stuff and the powdery stuff? I often see the foul black mucilaginous gunk in blocked wet systems and sometimes in poorly maintained first flush diverters. It could comprise of bacterial die off amongst the broken down organic matter and grit/dirt...I don't know. I might take a sample one day and have it lab tested. The fine powder like material that is diverted into our tanks is simply very fine suspended material that passes over the sediment trap(s). I emptied one of my poly tanks a couple of years ago when I replaced the square sand base with a round concrete one. It was the tank's first clean after 6 years and all I did was syphon it with a metal lawn sprinkler turned upside down on the tank's floor. The sprinkler was attached to a 12mm garden hose. When the tank was empty, I laid it on its side, tilted it towards the opening, gave the tank's inside walls a quick rinse and then scooped out what water I could. It was summer and when I came back a couple of days later, the water inside had dried up and all that was left was a fine powder that I vacuumed. This tank has been supplied by a minimum 2 downpipes and often by 4 downpipes via a wet system of my design, the number of downpipes diverted depending on how full/empty the tank is. The tank was only cleaned because it had to be removed, it certainly didn't need de-sludging. By comparison, the smaller tank that it replaced 6 years prior was cleaned after about 4-5 years but that tank was only supplied by one 'dry' system downpipe. I had to use a high pressure nozzle and a yard broom to scrub the bottom of the tank and the sediment was foul. einadia I spoke to the bloke at a local irrigation supply place this morning about a floating inlet, and he tried to talk me out of it, saying that with moving parts, something's bound to go wrong eventually - a crack at the tank outlet, letting sludge into the outlet, and/or deterioration of the flexible pipe that goes up and down and/or providing an extra surface for sludge, algae, bacteria, etc to stick to. If ignorance is bliss, then the irrigation bloke you spoke to must be a very happy chappy! The only part that (very slowly) moves is the hose and float and they are under no stress. The tank outlet is very strong and under no pressure from this fitting. The hose inlet is under the surface of the water...no sludge floating around up there. I suppose the irrigation bloke conversely thinks that a low outlet supplying the pump doesn't draw sediment...that is the only way to interpret his inanity. The hose is made from tough food grade polyethylene...the same material poly tanks are made from. The WaterBoy also has a 10 year warranty. Polyethylene is an inert plastic. http://www.harvesth2o.com/floatingfilte ... aERRvl8uXA einadia “we also divert wet system water into the tank via a low restriction inlet and this also oxygenates the anaerobic zone.” I’m having trouble visualising this and working out if it would apply to our system. As stated, this is for a wet system. You can use a calming inlet to achieve the same result in a dry system. einadia “it is never a good idea to have a sump in a transfer line as per your intended balance line.” What problems do you anticipate, Save H2O? By "balance line", do you mean the pipe that can fill one tank from the other? My understanding now is that the second tank will be 290mm lower than the first tank. As previously stated, this probably necessitates the pipe between the pump and the second tank to have a check valve fitted and if the pump is higher than the low water level in the second tank, then this has to be done anyway. This then also negates the use of the pipe between the two tanks as a balance line. I previously thought that there would be a separate balance line. A balance line is best not having a sump unless the flow rate is sufficient to flush any bed load. einadia Do you mean it’s best to have the overflow close to the inlet? Yes, you need to be able to reach the overflow outlet's mesh for maintenance or if you ever need to clean it. Using an old toothbrush is best. I see too many tanks that have an inaccessible overflow outlet and the overflow mesh clagging up is not uncommon. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Sludge in rain water tank 16Jul 13, 2015 1:40 pm Thanks for your further info, H2O. I have some more questions: Stewie, I’m puzzled about a couple captions in your diagram: “Anaerobic sludge layer in base of tank to assist water treatment” I don’t understand how the sludge can help improve the water quality (unless it is in a wastewater treatment system). Does it also apply to a rainwater tank to supply drinking water? If it does, how does it help? From reading research papers on what gets into rainwater from roofs, (eg by Mirela Magyar), I have the impression that metallic compounds and other pollutants attach to the sludge, and to maximise water quality, the sludge should be minimised, and water taken from above the sludge layer. “Biofilms on inside of tank assist water treatment and capture microbial contamination” I thought biofilms were layers of bacteria. Is this correct? If so, why would you want them inside your rainwater tank? Even if they inevitably get there, how could they help the water quality (unless it is a wastewater treatment system)? “Bottom of overflow pipe extends into anaerobic zone to remove sludge and sediment off bottom of tank” This sounds like a generic version of a TankVac. If what SaveH2O and people I’ve spoken to recently say is correct, and an outlet at the base of the tank would only remove sludge from a very small radius around the outlet, would a TankVac type of device also only remove sludge from a small radius around itself? Save H2O, you say “The overflow outlet's wire mesh can gum up and when this happens, the tank will over-top.” Would a flap valve instead of a fixed outlet on the overflow be a good idea to prevent it clogging? “you cannot have a low restriction inlet fitted to the first tank (if you have a wet system) because the system would remain flooded if you did.” What’s a low restriction outlet? Would you describe our system (with the only underground pipe connecting the two tanks to a pump) as a wet or dry system? “First flush diverters don't prevent sediment going into the tank” I accept that they wouldn’t stop all sediment going into the tank, but I can’t see how they wouldn’t stop some or even most. We’re thinking of having a system to manually override the first flush diverter (FFD), so that we can keep flushing when the roof is dusty and flush minimally or not at all when there have been frequent rains for long enough to clean the roof. We thought this would improve the performance of the first flush diverters. At the moment our thinking is to have one pipe coming out the side of the FFD with a valve, to keep flushing if we wanted to, and another valve at the top that can be turned off to prevent the water going into the FFD. “I also agree with bashworth's answer re rat tailing.” What’s rat tailing? I also have a question on another angle. At the moment we just have buckets under pops in the gutter (no tanks yet). I’ve been monitoring the water in the buckets every day for appearance and taste. Unless there has just been at least a few millimetres of rain, the water tastes bad. Originally, I assumed the taste was due to the new zinc galvanised roof and gutter (all done in about March 2012), but if it is due to the metal on the roof, I’m surprised that it takes this long to stop affecting the taste. Other things on the roof include 8 PV solar cells and stand; at times lots of dust (from sedimentary soil based mainly on siltstone); a few gumleaves, other leaves, pine needles and twigs; an occasional bit of bird poo. The sometimes bad taste has been consistent when it hasn’t rained for a day or so, and then there is a small rain or frost melting. What could be causing the bad taste? (It’s hard to describe the taste, but it doesn’t taste “off” like decaying organic matter.) I’d also be happy to hear from others about their experience with first flush diverters, leaf-diverting rain heads, floating inlets, TankVac-type devices, and any other gadgets, solutions or problems. Re: Sludge in rain water tank 17Jul 13, 2015 6:01 pm einadia Save H2O, you say “The overflow outlet's wire mesh can gum up and when this happens, the tank will over-top.” Would a flap valve instead of a fixed outlet on the overflow be a good idea to prevent it clogging? I have never seen one fitted to an overflow pipe but the manufacturer advertises flap valves as suitable for this purpose. http://rainharvesting.com.au/product/ta ... w-outlets/ einadia What’s a low restriction outlet? No idea. einadia Would you describe our system (with the only underground pipe connecting the two tanks to a pump) as a wet or dry system? Dry. It only refers to the infeed. einadia “First flush diverters don't prevent sediment going into the tank” I accept that they wouldn’t stop all sediment going into the tank, but I can’t see how they wouldn’t stop some or even most. Some, not most. Not all first flush diverters are the same either. Some are better than most. einadia What’s rat tailing? The suctional sphere of influence. einadia I’ve been monitoring the water in the buckets every day for appearance and taste. Unless there has just been at least a few millimetres of rain, the water tastes bad. What could be causing the bad taste? The atmospheric and other pollutants that are washed from the roof when it first rains is called the roof wash or first flush. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Sludge in rain water tank 18Jul 14, 2015 1:10 pm Thanks for your answers SaveH2O. It was a low restriction inlet (not outlet) I meant to ask about, re "Having mosquito proof leaf diverters also allows you to fit a low restriction inlet." I've figured out it probably means an inlet with minimal restriction ie fast flow. Is that right? Regarding the underground pipe the plumbers have already put in, we're having second thoughts about it. Our house designer warned us not to have the downpipe going underground before it got to the tank, as he said it would get stagnant water, algae, etc in. When the plumbers proposed an underground pipe connecting the 2 tanks, we told them what the designer said, and they said that wouldn't apply because the water would always be moving, but now we realise that if we have a dry spell and the tanks are nearly empty, we won't be using that pipe, and so the water wouldn't be always moving. Any comments? Also, the pipe is copper, and we suspect the health risks of a copper pipe are worse than that of UPVC or polyethylene. We could possibly have the connecting pipe go along the outside wall of the house (although there's a door in the way). "Not all first flush diverters are the same either. Some are better than most." Which ones are better? We're thinking of getting the Rain Harvesting one, which is the only one we've come across. "The atmospheric and other pollutants that are washed from the roof when it first rains is called the roof wash or first flush." What I'm wondering is which pollutant in particular is giving it the bad taste. I initially assumed it was the zinc from the new roof, but it's over 2 years old now. I suppose I could test to see if it's the dust by mixing up some dust from somewhere not on the roof, letting it settle, and tasting the water. The Your Home Technical Manual (yourhome.gov.au) has a diagram of a rainwater tank system with a “desludging valve” at the bottom. Bashworth and SaveH2O, if what you say is correct, the labelling of this diagram appears to be misleading. Would you agree? Re: Sludge in rain water tank 19Jul 14, 2015 10:57 pm einadia It was a low restriction inlet (not outlet) I meant to ask about, I've figured out it probably means an inlet with minimal restriction ie fast flow. Is that right? Yes. An example of a low restriction outlet would be fitting a flap valve to the overflow outlet to eliminate the outlet's wire mesh which will typically have a 53% open mesh area. Another example would be to fit a larger outlet valve and hose to supply a pump that was some distance from the tank. A wet system low restriction inlet is simply an inlet valve (typically 40mm) that is fitted about 100 mm above the bottom of the tank at the valves lowest point. The valve is connected to a flexible UV stabilised hose (typically Clearpond pondflex) that in turn connects to a same sized DWV pipe. The small DWV pipe then connects to a 100mm DWV tee at the base of the wet system vertical riser via a reduced size fitting, typically a 100mm x 50mm/40mm pipe reducer or a 100mm x 50mm invert taper. http://www.clearpond.com.au/products/al ... ccessories The flow path has priority flow because it operates with more head pressure than the vertical riser because the tank's variable water level will always be lower than the top of the vertical riser. The flow is also higher velocity due to the smaller pipe plus the flow path provides a minimum rise in elevation unlike the vertical riser. There are many advantages to using a low restriction inlet and these were all lessons that we learned through the initial Supadiverta research and development program. It was during this research period that we found that the common rainwater harvesting methods used were very much sub standard. That led to developing the Supadiverta that uses syphonic drainage to divert first stage filtered water through small pipes to a low restriction inlet, i.e., NO vertical riser. It was then realised that the methods used could also be used to significantly improve standard wet systems by improving the water quality, increasing yield and supplementing the wet system's flow rate during heavy rain. einadia Our house designer warned us not to have the downpipe going underground before it got to the tank, as he said it would get stagnant water, algae, etc in. When the plumbers proposed an underground pipe connecting the 2 tanks, we told them what the designer said, and they said that wouldn't apply because the water would always be moving, but now we realise that if we have a dry spell and the tanks are nearly empty, we won't be using that pipe, and so the water wouldn't be always moving. Any comments? Your house designer obviously has knowledge about standard wet systems and he is correct. The water in the pipe should be clean because it comes from the tanks and because both tanks have infeed, the pipe can be small which will generate higher velocity than a large pipe. I wouldn't have any concerns. Are you having any sort of filtration? einadia Also, the pipe is copper, and we suspect the health risks of a copper pipe are worse than that of UPVC or polyethylene. Polyethylene is food grade and inert. uPVC pipe use to contain lead but it no longer does. Not all uPVC stormwater and DWV pipe is certified to AS/NZS 4020, products in contact with drinking water but that is not what the product is designed for. I know of one manufacturer that does certify their uPVC stormwater pipe to AS/NZS4020 but plumbers still issue compliance certificates when they use non AS/NZS 4020 certified uPVC stormwater pipe in rainwater systems even when they know that the water is plumbed for potable use. The regulatory bodies turn a blind eye to the practice. Rainwater is naturally acidic and becoming even more so due to the continuing elevated levels of carbon dioxide (CO2) in the atmosphere. Acidic water reacts with copper and copper piping should never be used with rainwater. You can alter the pH by adding a nylon bag of limestone chips into each tank, just tether a small float to the bag for easy retrieval. Adding bi carbonate of soda also does the trick. Because rainwater lacks minerals, some householders also add Epsom Salts if the water is used for potable purposes. einadia "Not all first flush diverters are the same either. Some are better than most." Which ones are better? You first need to know the roof area diverted to each FFD. Most FFDs use 90mm (OD) uPVC stormwater pipe, the ID is usually 86.2mm. This gives an internal volume of 5.83 litres per metre. 100mm SN6 DWV pipe has an OD of 110mm and an ID of 104mm. This gives an internal volume of 8.5 litres per metre, 46% more than the 90mm uPVC stormwater pipe. If the roof area was let's say 40 sq m (including gutters) plan area, it would only take an insignificant 0.3mm of rain to fill a two metre long 90mm first flush diverter. Using a 100mm pipe and a longer length is better. When most first flush diverters are full, an internal ball rises and seals the top to prevent a venturi effect (supposedly) recycling the flush. Most debris and bird droppings are washed from the roof and gutters during heavy rain, long after the first flush is full but remember the ball seal? It also diverts muck over the top to the tank. FFDs with drippers are responsible for a lot of yield loss. A tap dripping at 1 drop per second (not apothecaries measure) will lose about 13.5 litres per 24 hours but many FFDs flow with a steady stream and this is during the entire rain event and afterwards as the diverter empties. Annual yield losses can be significant. SUMMARY: It is best to use a 100mm pipe of maximum available length and have a manual drain facility rather than a dripper. If you go to JNK40's Gympie thread, you will see a FFD on his garage. The FFD is DIY and made from a tee at the top, a pipe, a 100mm bracket cap with a 19mm outlet spout at the bottom with some 19mm polypipe and an inline tap attached. The amount collected is known and it can be collected. If it was to be drained, a longer poly pipe would be used. A floating ball is not needed because the pipe is deep and the water settles. The photos are also below. See if you can identify several examples of a plumber's lack of knowledge in the photo below. There are 2 vertical risers and 2 FFDs supplied from multiple downpipes. einadia "The atmospheric and other pollutants that are washed from the roof when it first rains is called the roof wash or first flush." What I'm wondering is which pollutant in particular is giving it the bad taste. No idea. You can get water tested if you are really interested but it could be general atmospheric pollutants. Water that has a dissolved oxygen (DO) level less than 1 mg/L is considered anaerobic and is said to taste foul. Maybe bacterial activity breaking down dissolved bird droppings has depleted the DO levels but I wouldn't think that it would be that fast. Maybe the taste comes from the bucket. einadia The Your Home Technical Manual (yourhome.gov.au) has a diagram of a rainwater tank system with a “desludging valve” at the bottom. Bashworth and SaveH2O, if what you say is correct, the labelling of this diagram appears to be misleading. Would you agree? Yes. It shows a misunderstanding as only the immediate zone is cleaned. There are also several mistakes shown in other diagrams and photos but it is easy to find fault in reports and advice by 'experts' in this field. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Sludge in rain water tank 20Jul 16, 2015 3:43 pm Thanks again SaveH2O. You asked: “Are you having any sort of filtration?” No, we’re not. You said “I know of one manufacturer that does certify their uPVC stormwater pipe to AS/NZS4020” Which manufacturer? I have the impression that the difference between food grade and non food grade polyethylene is the smoothness of the surface (to minimise bacteria habitat) rather than the chemistry of the plastic. Is that correct? “You can alter the pH by adding a nylon bag of limestone chips into the tank” Where do you get limestone chips? I presume this sets up a chemical reaction which eventually depletes the limestone, which then needs replacing. Is this correct? I wouldn’t like to add sodium bicarbonate – I try to minimise my sodium intake, for health reasons, and also minimise what goes into the soil, as high levels damage plants and soil. “You first need to know the roof area diverted to each FFD.” The total roof area is c. 175 sq m, divided equally between 2 first FFDs, which gives c. 87 sq m per FFD. (This area doesn’t include the gutter – which is half round and 16.8m long.) The roof is at a pitch or about 7 deg. Re water taste, after reading/re-reading a few papers (Magyar et al 2006, 2007, Chapman et al 2006) on what gets into rainwater from roofs, I’m again thinking the taste could be from the zinc on the galv. roof. If so, I wonder how long it will take to go away. I grew up drinking rainwater from a house with a galv. roof (40 years old when I was 15) and I don’t remember this taste. Can a plumber put a tap on a rain water tank which is full? Tank is similar to one in photo. Cheers. 0 1670 If you can calculate the reasonable charged head from let's say 100mm below the gutter to the top of where the vertical riser's horizontal discharge pipe will be, that… 11 17539 Building Standards; Getting It Right! Thank you for the generous offer. I need to get the plumber out to give me an explanation. As mentioned I haven't seen any rain water discharge from pipes 1& 3. It… 7 10834 |