Browse Forums Eco Living Re: My rainwater system design 4Apr 09, 2016 7:03 pm oneJohn I'm looking at installing the Leaf Eater Ultra leaf diverters. It seems they can be mounted right under the gutter, and so preserves as much head as possible. The ground at the base of the tank is about 2.6m below eaves level, and the tanks I'm looking at have inlets at around 2200. I can't recommend any of the current leaf diverters on the market and I certainly cannot recommend the Leaf Eater Ultra for your situation because amongst other 'issues', it is 395mm high and you would lose about 270mm head best case scenario. The Leaf Eater 'Advanced' is 242mm high, can also be mounted high and your head loss would be about 145mm best case scenario. You wouldn't connect a downpipe to the gutter, just have the pop. If you fit leaf diverters, you can then fit a low restriction inlet and this will supplement the flow rate. oneJohn Currently the downpipes are 75mm, but I'm thinking to change them to 90mm on the charged system, mainly because 75mm is such an odd size, and fittings are hard to come by. Then I'm thinking to go to 100mm before entering ground level. I assume that the downpipes are 75mm square as these have about the same capacity as the 90mm round downpipes. If the downpipes are 75mm round, they will be too small and not compliant. You have a 330 sq m roof and 9 downpipes. Downpipes don't harvest equal roof areas but for this explanation, we will recognise that the average roof area your downpipes drain is about 36.7 sq m. You are in a low intensity rainfall area and your 1:20 Average Recurrence Interval (ARI) will be either 110mm/hr or 120mm/hr. The 1:20 ARI is based on an average rainfall intensity over 5 minutes, if your 1:20 ARI is 120mm/hr, your 5 minute intensity average is 2mm/min. Eaves gutter roof drainage compliance is based on a regions 1:20 ARI and your water tank is also part of your stormwater drainage because the overflow will divert to the stormwater. For this reason, you water tank's overflow capacity must be either equal to or greater than the inflow capacity. You intend harvesting 5 downpipes to the tank, 5 x 36.7 sq m = 183.5 sq m of roof, giving an inflow during a 1:20 ARI of about 367 lpm. One of the failings of the rainwater harvesting industry is that tank manufacturers are not required to state what each tank's overflow capacity is. The tendency now is for manufacturers to make tanks with the need to install the overflow very high on the tank, most often on the top inlet's surround. This means that the tank has little mitigation and a restricted overflow capacity. It is easy to calculate the drainage rate through a tank's overflow when you know the overflow outlet's diameter and the maximum height the water can reach above the invert (the bottom of the opening) by using Torricelli's Law. The complication with rainwater tanks however is that the opening is meshed and the % of meshed open area is commonly in the low 50% region. Tank manufacturers also do not supply information about the open area % of the mesh they use. Your tank's meshed overflow outlet will obviously be 100mm and if we assume that the overflow mesh has 55% open area, the height of the water above the invert will need to be greater than three times the outlet's diameter in order to generate a full-flow rate to prevent the tank over-topping during a 1:20 ARI. Fitting a bell inlet to the overflow against the tank's wall inside the tank will increase the flow rate by about 30%. Water flows faster down a vertical pipe/opening inside a tank than through a horizontal overflow pipe fitted to the side of the tank, for example, a 100mm vertical drain pipe inside a tank will flow with 150mm of water above the opening at the same rate as would a 100mm overflow outlet fitted to the side of the tank and draining with 200mm of water above the invert. With just 50mm of water height, the vertical opening will flow about 3.5 times faster than the horizontal opening. Fitting an extended upturned elbow from the overflow inside the tank increases the flow rate and fitting a bell opening to the orifice will increase it even more. Removing the mesh and fitting a flap valve or mesh to the pipe outside the tank will allow a 100mm side overflow to flow at your required 367 lpm with just 135mm of water above the invert and fitting a bell opening or upturned elbow will increase the flow capacity even more. A second overflow pipe can be diverted to a shared vertical overflow pipe. The supplementary overflow pipe can be smaller than the first pipe. oneJohn The site is on reactive soil, so is there an advantage in using flexible couplings at any point? AS 2870 covers the requirements for reactive soils and houses. The second link in particular is a very good read. http://www.stormplastics.com.au/files/A ... enotes.pdf http://www.stormplastics.com.au/files/S ... arJuly.pdf Poly tanks can change shape and put a 'solid connected' overflow pipe under stress. This Storm Plastics link should interest you. http://www.stormplastics.com.au/files/S ... anks_1.pdf Drainage pipes buried in reactive soil are addressed in AS 3500.3. oneJohn I have in mind to add a silt trap as suggested. How do you normally mount the outlet of this? I can picture a poly pipe emerging from the ground - do you then tie it to a stake or something like that? You can extend it to a garden bed or anywhere you like, it just depends on what is convenient. Because the pipe is reduced, it also flows with increased velocity. Have a read of a poster's one year summary after installing a 4 tank settling system that was designed for his (S.E. QLD) rainfall pattern. viewtopic.php?p=1146540#p1146540 oneJohn Then there's the low restriction inlet. I assume with this that you need a valve on the tank inlet, so you can close it off to open the sediment purge? One thing I wonder is if using the 100mm Tee section, the geometry could be awkward around the tank. The riser would be close to the tank, so the base of the tee is going to be headed away from the tank - can you than have sharp bends to bring it back into the base of the tank? One thing I am wondering is with the low restriction inlet, is there still need for the riser? The sediment trap was developed during our ongoing Supadiverta field testing, it is very efficient and it has many advantages. The Supadiverta is a syphonic bottom inlet tank infeed system and the way we connect the infeed pipe to the tank is the same method you use to connect a low restriction inlet from a standard wet system to a tank's bottom inlet. You would still require a vertical riser but it would only see use during heavy rain. To fit, we connect a poly director to a length of PondFlex at the pipe end with either another poly director or (preferably) a nut and tail fitted to the opposite end. The fitting is then connected to a tank valve fitted about 100mm above the bottom of the tank at the valve's lowest point. The low restriction inlet should also be within 75 degrees either side of the tank valve that supplies the pump (unless you use a floating inlet like a WaterBoy). The poly director is then fitted to a faucet socket (a pipe joiner with a female fitting at one end) and solvent welded to the pipe. This is done last. If the hose should ever need removing, fitting a nut and tail at the tank end makes it easy. See photos 11 and 12 in the link below. Note that the photos show 32mm PVCu pressure pipe, the faucet socket will need to be substituted with a DWV fitting. http://supadiverta.com.au/pipes---fittings.html We invariably fit an elbow to the low restriction inlet so that the PondFlex hose comes up at an angle. You require head pressure that will deliver about 367 lpm during a 1:20 ARI and with the height of water in the top of the vertical riser above the tank, you will have about +200mm of head. 100mm SN6 DWV pipe has an internal diameter of 104mm, giving an internal volume of 8.53 litres per metre. You will have a long run of drain pipe but a quick check shows that 100 metres (pipe length and allowance for the fitting's friction losses expressed as pipe length) of 100mm DWV pipe requires nearly 0.5 head to flow at 366 lpm. A 200mm head will only give you 225 lpm and a best case scenario 250mm head will give you 255 lpm. If you take the worse case scenario of a 200mm head, you need another 140 lpm flow capacity into the tank. My guesstimate of 100 metres of friction loss is just that but I think that I would be fairly close. The low restriction inlet operates with greater head pressure due to the height difference between the water in the tank and the height of the water at the top of the vertical riser. Assuming a worst case scenario of only an additional 200mm head when the tank is full, i.e., 400mm head pressure when the tank is full, a 40mm hose and low restriction inlet would be very much borderline whereas a 50mm inlet would have plenty of additional capacity. oneJohn What's the best way to get the extra drillings into the tank? Is that something you order the tank with, or drill them through later? Are some tanks easier than others to do this? You option the tank with the fittings and overflow outlet in the size and position you require. Note that the manufacturers often refer to the valve heights as being their central point. Don't forget to query them on their optimum overflow pipe options. 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: My rainwater system design 5Apr 10, 2016 8:28 pm Thanks for all the info on that, it helps fill out more details in addition to your posts I've been reading in other threads. It's a shame that your new diverter isn't ready yet, but it comes down to what's available. I did like the look of the supadiverter, but as you mentioned before, it was going to have troubles with the head. I thought that the leafeater ultra wasn't too bad in head loss due to the rear exit design being part of the height, but the "advanced" does lose less. Our downpipes from the builder are 75mm round, which seems to be the most common in new builds in Adelaide. It seems silly through, especially seeing as the fittings for 75mm are expensive. I was planning on changing them to 90m when adding the diverters I'll have to research the fittings a bit more, but I'm still wondering a bit about the drain pipe for the sediment trap. Some pictures I've seen show 40mm (DWV?), and others smaller, down to 20mm or so. Is the size on this important? I imagine that smaller tube will flow faster, but eventually have a higher risk of blocking. Do you need to be careful not to have sharp elbows on this line? I went to a place that sells and installs tanks the other day. I asked what leaf diverters they had, and at first he didn't know what I was talking about, and then said that they never used them. Similarly, they wouldn't think to use mesh or flap valves on the overflow, and no thought of anything but the simple wier type overflow connection. The industry just seems unaware of the different things you can do to improve rainwater collection. Re: My rainwater system design 6Apr 11, 2016 3:04 am oneJohn I wonder if perhaps the sediment purge should be reduced down to 40mm at the bottom of the trap, but don't want to make the design for the plumbers too complicated. When it reaches ground level, I'll then have to terminate it to some sort of valve that will point in a sensible direction to purge the silt. To reduce 100mm DWV to 40mm, you just buy a 100mm x 40mm pipe reducer. This will fit into the DWV tee or 45 degree wye junction. Note that like many pvc fittings, they can also be referred to by another term as per below. http://www.pvcpipesuperstore.com.au/100 ... -498-p.asp We usually use a 100mm wye fitting for the sediment trap because the 'trap' opening is larger and the bottom fittings don't go as deep. Finding a wye with an inspection opening can be difficult as the major manufacturers don't make them and they are not cheap. The wholesaler that I get mine from has also been out of stock now for some months. The only use for the opening is for 'insurance' in case a large object travels down the pipe and lodges against the smaller opening but if you have leaf diverters, this won't happen. Tees with an inspection opening (IO) are easier to find and Holman make one but the retail prices vary wildly...from $15 to $40. The first 100mm DWV trap that I bought a few years ago was an iplex tee with an IO and I paid well over $30 at Reece. I saw the same one a few weeks later for half of what I paid. The iplex one is shown in the link below. http://www.comhardware.com.au/Product/J ... cat=136140 If you are comfortable with not having an IO, just use a (much cheaper) plain wye junction or a tee. I have been testing an improved version of the current wye junction sediment trap that eliminates the 45 degree elbow and the pipe reducer. I have always been a bit annoyed about the pipe reducer's design because it has the potential to build up debris in the cavity around where the smaller pipe fits. If you look at the inside area, you will understand why. This material is however subjected to flushing and poses no risk but I don't like it because it isn't as good as it should be. The reducer will fit directly to the wye junction (and eliminate the larger elbow) and a 40mm M F 45 degree elbow then fitted to the reducer but the accumulation of debris is greater because it is on a slope as opposed to being horizontal when fitted after an elbow as per the diagram below. I was thinking of devising a way to fill the reducer's inside wall cavity with some readily available food grade substance so that no debris was trapped but I think that suggesting this to others would be impractical. I am now playing around with having a 100mm x 50mm invert taper fitted directly to the wye junction and either a 45 or 90 degree M F elbow fitted to it. A 50mm DWV female iron adapter would then fit into the elbow and a 50mm x 25mm poly bush would then fit to the adaptor. A 25mm poly director would then fit to the bush, that then allows a 25mm poly pipe to be used. This fitting is about 10mm deeper than the current one but the captured bed load has a smooth downward transition and the poly pipe is more versatile and cheaper. There are several other options. 100mm x 50mm inverted taper. DWV female iron adapter. Threaded poly bush. Poly director. 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: My rainwater system design 7Apr 12, 2016 8:53 am AS 2870 covers the requirements for reactive soils and houses. The second link in particular is a very good read. http://www.stormplastics.com.au/files/A ... enotes.pdf http://www.stormplastics.com.au/files/S ... arJuly.pdf I second that... very good read indeed. So this is what should be specified on drainage plans for reactive sites? How many builders, designers or surveyors would even know? Re: My rainwater system design 8Apr 12, 2016 12:49 pm You can also throw plumbers, architects and hydraulic engineers into that mix for all manner of things. 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: My rainwater system design 9Apr 12, 2016 1:10 pm That's for the extra details. That helps make it clear. With the flexible poly pipe it should be easier to find a neat way to terminate it above ground. There is some quite serious variation in the cost on the tee with inspection opening. Bunnings have the Holman one for $40, and there's this place that has one for $11: http://www.pipeonline.com.au/listProduc ... S+JUNCTION It's probably not worth it after the shipping, but it might be worthwhile to get a few things at once. Re: My rainwater system design 10Apr 12, 2016 3:51 pm If they are in the trade Liliana - plumbers, electricians, concreters, builders etc and building on reactive soil, then as professionals they should know. Not to do so is just ignorant and amateurish. Stewie Re: My rainwater system design 11Apr 12, 2016 3:57 pm Onejohn, Pipeonline are wholesalers but the Bunnings one is very expensive. Postage is a trap with some online traders and you have to be careful of their charges. It wouldn't be worth buying a one off plumbing fitting. Most irrigation stores are much cheaper than Bunnings and other hardware stores. 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: My rainwater system design 12Aug 21, 2016 5:10 pm Hi John Are you done, moved in and have full tanks? In the end did the builder install 75mm downpipes? With all this rain I've been cursing that we don't have a roof or downpipes to start filling tanks! We hope to at least have the slab poured by Christmas on our H2P site in Adelaide. Im interested to hear how you have got on. There is a whole lot more to know than just the answers you seek but they are a good start. Overflow outlets have a mosquito proof mesh. These… 3 9200 Grate, thank you! RexChan if thats the reason i could sleep well without thinking about additional cost. But 1st i'll need to read about NRV cleaning/replaing stuff. I… 7 31987 |