Browse Forums Eco Living 1 Dec 09, 2016 5:13 pm So we are building a house in ACT, and are going to put in a 10kl tank. Normally tanks are used for toilet, laundry and garden. In ACT if you then want to use it in showers, it has to be brought up to drinking water safe standards. Does anyone have any idea on what the different requirements are, and how expensive the difference will be? We understand that we will require first flush diverters, and maybe filters. Anything else? For info, the house will be on a flat block, two stories, and have a flattish roof. The diagram here shows what I mean. The red roof is the main roof, and is about 110m2. The blue and green roofs are 36m2 and 20m respectively. The grey is the 10kl water tank. and is on the low side of the main roof, and can be directly fed by the required downpipes. Main toilets and showers are upstairs. I have looked at the ACT guidelines for water tanks, and reckon that if we use the red roof only, we can get 60kl of water per year, or the red and blue then about 85kl. Adding the green would give us about 90kl so only a small gain. Edit: Just found a more detailed water usage/savings calculator on the ACT Government's Planning website. I presume due to greater detail, it is more accurate than me trying to read values off a simple graph in that first publication. This includes first flush diverters etc... and drops the benefits by about 10% at the tank sizes we are looking at. Re: Water Tanks - Difference to make "drinking" safe 2Dec 10, 2016 7:45 pm A quick Google tells me that Canberra water charge is around $5/kl, thus your 10,000l tank holds the equivalent of $50 worth of water and you are going to spend how much on this exercise? Presumably the Council mandate a water tank. Go through the motions and spend the minimum. I'm sure that there are some worthy charities that would make better use of your spare cash. And rain water down the drain is not wasted - it all goes back to the environment in one way or another. Re: Water Tanks - Difference to make "drinking" safe 3Dec 13, 2016 10:56 pm Harpies .....your 10,000l tank holds the equivalent of $50 worth of water and you are going to spend how much on this exercise? The OP has not stated a cost but the premise that the cost will only result in one tank full of water is absurd. The benefits of utilising a precious resource like rainwater goes beyond pseudo greenie ROI considerations. Harpies I'm sure that there are some worthy charities that would make better use of your spare cash. What anyone chooses to do with their "spare cash" is their business. 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: Water Tanks - Difference to make "drinking" safe 4Dec 13, 2016 11:58 pm planeguy So we are building a house in ACT, and are going to put in a 10kl tank. Normally tanks are used for toilet, laundry and garden. In ACT if you then want to use it in showers, it has to be brought up to drinking water safe standards. Does anyone have any idea on what the different requirements are, and how expensive the difference will be? We understand that we will require first flush diverters, and maybe filters. Anything else? The requirements will almost certainly be referenced Australian Drinking Water Guidelines (ADWG). Guidelines are only guidelines unless mandated and many regional water supplies often fail to meet the ADWG. It is possible but not probable that the A.C.T. has mandated its own criteria for what constitutes ‘drinking water’ and perhaps you should ask for their reference to the “drinking water standards” when there are no Standards that I am aware of. If there are any mandated Standards, then I stand to be corrected. Your property is well designed for rainwater harvesting and the focus should be on having good quality water diverted to the tank and the best quality water in the tank diverted to the pump but most pumps receive the worst quality water in the tank! Once you have set up the system, the most suitable water filtration can be looked at after you have decided on the usage and had the water tested. Reasonably cheap home testing kits are also available. For potable use, if a well designed system supplies lab tested confirmed good quality water to the pump, then a 10 and possibly a 2 micron washable filter should be all that is needed for ‘insurance’. The filters should have an easy life. I will go over the best practice basics and also mention the traps to avoid so that you can have an informed discussion with your architect. ROOF DRAINAGE Eaves gutter and downpipe compliance is determined by an area's 1:20 Average Recurrence Interval (ARI). The Canberra 1:20 ARI is 140 mm per hour which is based on an average rain intensity of 2.33 mm per minute over a 5 minute duration. The Canberra average annual rainfall is 629 mm and a good rain harvesting yield is about 85%. I think that the 10,000 L tank is a good size but the 110 sq m house roof area is small. I think that you should harvest all of the 166 sq m available roof area. 166 sq m x 629 mm x 0.85 = 88,752 litres or about 243 litres per day. Canberra references both the Australian Standards and the lesser BCA (but the BCA is the primary document as per hierarchy) for roof drainage compliance. You are fortunate in having straight runs of guttering but compliance does not factor straight runs or the use of superior gutter designs. It is important to have clean gutters for collecting good quality rainwater and for maximum first flush efficiency. The best draining and flushing gutters are the D and the half round gutters. Having either of these gutters fitted to the house and draining to a central 100 mm downpipe would be the most efficient, neatest and cost effective method but for compliance, you will need two 90 mm uPVC downpipes fitted at the low points along an elongated W gutter slope. Do not have a downpipe at each end of the gutter with a high point in the middle as most have. The 90 mm uPVC stormwater pipe commonly used for downpipes has a flimsy 1.9 mm thick wall but a stronger 2.5 mm thick walled SN4 rated pipe is available. I don't know the heights of the green and blue roofs or the height of the tank but you need to check this before determining whether you will have a wet or dry system from these two areas. A Canberra 1:20 ARI will produce 166 x 2.333 = 387 lpm. If a wet system is used, a single 100 mm sub surface DWV pipe is ok subject to the available head between the blue and green roofs and the top of the tank's vertical riser. FIRST FLUSH First flush is the initial dirty roof wash but most roof and gutter detritus including solid bird droppings is flushed to the downpipe during heavy rain, long after first flush diverters are full. Metal roofs are better for rainwater harvesting than tile roofs as the metal roofs are flushed much quicker. Metal roofs also have a sterilising effect on bird droppings. First flush diverters reduce yield considerably because most have drippers that drip throughout the entire rain event and invariably the drip rate is greater than the usually recommended one drip per second. One drip per second (NOTE: NOT Apothecaries' measure) is approximately 13.5 litres per 24 hours and if there is a steady stream rather than a drip, yield losses can be significant. Total yield losses of 35-40% are common in areas like Melbourne that have prolonged periods of drizzle and light showers. First flush diverters with slow drippers also have an internal filter to prevent the dripper from blocking and the filter requires regular cleaning. Taking the bottom screw cap off a diverter with a blocked dripper to access the filter can be a 'wet' exercise. A standard 90 mm uPVC stormwater pipe has an internal diameter (ID) of 86.2 mm, giving a volume of 5.83 litres per metre whereas a 100 mm DWV pipe has an ID of 104 mm and a volume of 8.5 litres per metre, 46% more volume. A standard 90 mm first flush diverter is usually inadequate, for example, if your smallest 20 sq m roof area had a 90 mm first flush diverter two metres long, it would hold 11.7 litres. This means that it would fill with less than 0.6 mm of rain; hardly enough to flush the roof, in fact, most of the flush would come from the roof area nearest the downpipe! You have probably seen photos on Homeone and elsewhere that show first flush diverters fitted to the top of wet system’s vertical risers. These are amateur installations because the water that fills the first flush diverter when it first rains is the settled water retained in the vertical riser while the actual first flush is still in the downpipe at the end of the wet system! Even if the wet system is drained after each rain event, the water that refills the wet system pipes and then rises up the vertical riser is very diluted by the time it enters the first flush diverter. Such installations are very common but are a waste of money and water. It isn’t hard to pick the faults with the first flush diverters in the photo below... The most efficient first flush diverters are those that collect a set amount and don't have wasteful drippers or internal filters. These require manual emptying by opening a drain valve and the water can be recycled on the garden. A property owner on one of the Homeone rainwater harvesting threads used one of my company's 100 mm first flush caps to fit a 100 mm DWV pipe under a 100 mm DWV diverted horizontal downpipe and this provided a maintenance free high volume first flush diverter. See photos in the post below. viewtopic.php?p=1146540#p1146540 I always use clear solvent cement but note that the pipe and cap were not painted when the photo was taken. I am considering making the bracketed cap available to the public so they can make their own low maintenance 100 mm first flush diverter but I haven't decided to as yet. If you wanted to go this route, I would supply some bracketed caps to you free of charge. First flush can also be diverted from all downpipes to a single first flush tank. To do this, the downpipes need to be plumbed to an underground (wet system) 100 mm DWV (Drain Waste Vent) SN4 pipe and a reduced 40mm DWV pipe coming off a tee at the bottom the vertical riser would connect to a smaller first flush tank/drum via a low fitted 40mm inlet valve. The flush tank, being low, would be air tight and a mosquito proof vertical vent pipe fitted to the top of the tank would need to rise higher than the 10,000 litre tank. The vent pipe would best be located on the drum’s floor and two holes drilled into the pipe at the level you wanted the tank to fill to. A 200 litre plastic drum or pickle barrel is commonly used and they can be purchased for $20 or less. First flush diverters are most effective after a long dry period but not so when there is a period of continuous rainfall. The single flush tank provides the options of recycling the water or not draining the flush during an extended wet period. A one way valve is often fitted to the infeed line. The first flush tank in the photo would be best located further away from the main tank’s vertical riser, the inlet should be fitted to the bottom and not half way up the flush tank and there only needs to be a single outlet flush valve fitted to the flush tank. WET SYSTEM Wet systems are usually troublesome but they can be better than dry systems if done correctly. One way to send good water to a tank is to fit a DIY sediment trap to a non turbulent section of the wet system to collect and later flush the slow moving bed load (settled suspended sediment). Doing this will remove more sediment than a standard dry system. The diagram below shows a sediment trap fitted to a 100 mm DWV pipe. OVERFLOW PIPE A half full 10,000 litre tank will fill with 30 mm of rain (excluding first flush) off the 166 sq m roof. Canberra has had several days this year when the daily rainfall was nearly 30mm and on June 6th, 28.4 mm of rain fell BUT the next day, 65.2 mm of rain fell. The overflow pipe’s drainage capacity must be equal to or greater than the inflow capacity and the inflow capacity during a 1:20 ARI is 166 (sq m) x 2.33 (mm per min) = 387 lpm. AS/NZS 3500.3 Figure 8.2 RATE OF OUTFLOW FROM TYPE 1 OVERFLOW (PIPED) HORIZONTAL OUTLET STORAGE TANKS states that a 100 mm overflow pipe with 100 mm of water above the pipe’s invert (the bottom of the pipe) will flow at 4.67 litres per second (280 lpm). This figure is less than the 1:20 inflow off the 166 sq m roof areas BUT the overflow orifice is also fitted with a flow restricting mosquito proof mesh that typically has an open area of little more than 50%. The Figure 8.3 flow rates do not account for restrictive mesh. Of interest, the flow through a tank's horizontal outlet is calculated by Torricelli's Law. To increase the overflow rate, a bell mouth orifice can be fitted to an upturned elbow inside the tank but my suggestion is to seriously consider fitting a TankVac syphonic over flow system that also improves water quality. The TankVac draws water through holes in small uPVC pipes that spread across the tank’s floor and an exterior 80 mm DWV vertical overflow pipe discharges into a larger pipe. The 80 mm pipe is primed by the TankVac and once primed; it vacuums sediment and the worst quality water from the anaerobic zone at 9 litres per second. This has a major positive effect on the tank’s water quality. Overflow is lost yield but it is worthwhile when a TankVac is fitted. The TankVac will not syphon the tank dry. https://www.youtube.com/watch?v=e1_B9WITe94 MAINS WATER SWITCHING DEVICES Plumbing rainwater into the house mains water pipes requires either a manual or automatic mains water switching device to be fitted in case the tank empties. Check valves are also required to be fitted to prevent rainwater from entering the mains water line during maintenance of the mains supply pipe. Some of the automatic devices are expensive and known to be unreliable. The MainRain is a well priced simple manual device that also has a check valve. http://www.mainrain.com.au/MainRain%20e ... ochure.pdf If you think that the systems storage capacity and local rainfall pattern does not warrant plumbing to anything other than the toilets, an additional laundry tap and a garden tap or two, then you could eliminate the expense of having a mains water switching device and check valves by plumbing a separate pex pipe directly from the pump or filter to the end fixtures. The ACT Guidelines on water tanks discusses this plumbing option. The toilet cisterns have to be suitable for the twin cistern valve system. PUMP Most pumps are inefficient and have a hard life when supplying a house needs. There are frequent short duration and slow flow demands that strangle large pumps and if you fit a pressure tank to reduce the number of stop/starts, the pressure to a shower will fluctuate. For whole of house use, a quality variable speed drive (VSD) pump like one of the Grundfos range is unbeatable. VSD centrifugal pumps also have a ‘soft’ start and are energy efficient because the energy requirement is cubed to double the pump’s speed. For non potable house use, probably the best value pump around at the moment is the Einhell 550W equipped with a pre filter and a 20 litre pressure tank. These are available in Bunnings for $299. The 20 litre pressure tank will have a draw down of approximately +6 litres, meaning that the pump will only come on every third ½ flush on a 6/3 L cistern and because it fills the pressure tank when it does come on, it will be operating at peak efficiency. https://www.bunnings.com.au/einhell-550 ... e_p4816143 If you have a submersible pump that draws water from the bottom of the pump, make sure that it is located above the sediment layer as will be required by the pump’s conditions of warranty. A common cause of dirty cistern water and clogged washing machine filters (or frequently dirty filters) are submersible pumps that sit on the tanks floor happily vacuuming the sediment. If you decide to have an external pump, make sure that the tank’s outlet valve that supplies the pump is not fitted close to the tank’s floor. The only time that an outlet valve can be fitted close to the tank’s floor is when the tank is fitted with a floating meshed outlet that draws the best quality water from about 200 mm under the upper water levels. Many people make their own or get an irrigation outlet to make one but they are also commercially available. http://www.crystalclearwater.com.au/waterboy/ External pumps need to be sheltered by a well ventilated cover that is preferably not exposed to the sun. LEAF DIVERTERS Wet systems in many areas are mandated to have leaf diverters but they should be compulsory on all wet systems. Water on organic matter bonds with water on wire mesh and this is the cause of a lot of splash and lost yield. Remarkably, some leaf diverters don’t fully drain while others have a wire mesh profile that acts as a debris trap. The ICON Leaf And Debris Controller has a hard plastic outer mesh on a good slope and an internal mosquito proof mesh that is removed by pulling out a drawer on the lower front panel but this can prove difficult at times when you are up a ladder. Having an outer filter on a functional continuous slope means that it is larger than most but thought has gone into the design to try and overcome the common leaf diverter problems. It is $38 in Bunnings. https://www.bunnings.com.au/icon-300mm- ... d_p4760074 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: Water Tanks - Difference to make "drinking" safe 5Dec 14, 2016 11:25 am Wow, that is a thorough response. It might take me a couple of detailed readings to get all the information out of it. Thanks a alot. To add a little more info: The Red roof is 6.1m AGL on the tank side. The Blue and Green roofs are 2.7ish AGL. The water tank hasn't been "designed" yet, and I had just made an assumption that it would sit on ground level, but need not. Similarly, we haven't picked the tank profile yet, and up to this point I had only been thinking something short enough to fit through the carport (blue roof), but happy to consider shorter, or taller options. (underside of blue roof is about 2.4-2.5m). Now, I have done some more reading, and have a "minor" problem. The green roof will have a wood fired chimney running up through it, and some sites say that this therefore makes it unsuitable for potable water - but still good for garden/laundry. From what you are saying, we might have the opportunity at this point to "choose" wet system or dry system, but then say that wet systems can be better but more troublesome. What factors/tradeoffs should we consider to make the decision? My gut feel at this point is the increase in pump system complexity for the shower and the loss of use of the green roof eliminates the advantages of going to the showers. But will keep analysing. Once again, thanks for the detailed response. Re: Water Tanks - Difference to make "drinking" safe 6Dec 14, 2016 1:20 pm planeguy From what you are saying, we might have the opportunity at this point to "choose" wet system or dry system, but then say that wet systems can be better but more troublesome. What factors/tradeoffs should we consider to make the decision? SaveH2O Wet systems are usually troublesome but they can be better than dry systems if done correctly. I'll give a reply later tonight when I have time and explain with example photos why standard wet systems are the 'pits'. They should be avoided at all costs. I would still direct connect to a dual cistern valve WC system and also to a separate laundry cold water tap, this can be done without the need for a mains water switching device or check valves. The value of connecting to toilets is not what it use to be when cisterns were single flush 12 or 13 litre units and utilisation of course also depends on the number of occupants, the amount of time they are home and even how much coffee (and other beverages) they drink. The average person flushes a toilet six times a day. Switching to cold water clothes washing is a great way to utilise rainwater and the added benefits include water heating cost savings, softer towels etc and needing less laundry powder/liquid. I often do a second rinse cycle and I also have a simple 2 way diverter on my outside laundry pipe so that I can divert the rinse water to the garden during the warmer drier periods. Are you planning to have a metal or poly tank? If you have a metal tank, it has to sit on a slab. I assume by the roof slope that the tank will be on the south side which is good. You don't always need a concrete base, the poly tanks in the photo sit on compacted sand bases 80 mm below the surface. Were you planning to have a submersible or an external pump? 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: Water Tanks - Difference to make "drinking" safe 7Dec 14, 2016 2:56 pm SaveH2O Are you planning to have a metal or poly tank? We have got as far as knowing we want a tank - not what type SaveH2O Were you planning to have a submersible or an external pump? See previous answer As a follow up, can the washing machine be connected to a tap with failover to mains if the tank runs dry, similar to the functionality of the duel cistern loo? Re: Water Tanks - Difference to make "drinking" safe 8Dec 14, 2016 5:55 pm It is best to have separate mains and rainwater cold water taps. When you have a tank, you are generally aware of the water level and it is easy enough to manually switch taps. A dual cistern valve cistern has an air gap that prevents cross contamination plus the wall isolation valves are the manual change over devices...one is off while the other is on. Practically all cisterns have two bottom entries for the valve. I always use the Fluidmaster 400UK063 valve because it is compact, cheap ($20 in Bunnings) plus you can get an optional low pressure valve seal or a very low pressure gravity fed valve seal (242LP071) to replace the standard high pressure valve seal. This is easier on the pump. 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: Water Tanks - Difference to make "drinking" safe 9Dec 16, 2016 7:18 pm SaveH20, so, looking again at the numbers, I think we have confirmed our thoughts. Potable water from 150m2 of roof area gives 1kl of extra available water per year. For looking at your guidance/costs etc... we are instructing our architect to go down the 170m2 option. Now he will adjust the roof fall so that the Blue roof's gutter will be on the right side as drawn , and the green on the near edge. He was thinking a wet system, to minimise the visibility of the guttering. I don't think we matter much about the look over that side of the house, but may agree. Reading up about tank types, it looks the material choice is fairly even for our use case in metal vs polymer types. Metal 10kl tanks look to be about $300 smaller, but look better. Do you think there is any performance difference? I also read up on external vs internal pumps - I like the ability to maintain a pump easier if needed, so am leaning towards external. Can you comment on the W gutter, versus one downpipe on each end of the gutter - why is that preferred? Similarly, does that mean on the small roofs that will have a single downpipe, does that mean they should have a downpipe in the middle and not the end? The architect won't like the look of that, so what's the purpose? Thanks again for all your advice. Re: Water Tanks - Difference to make "drinking" safe 10Dec 17, 2016 12:08 am planeguy He was thinking a wet system, to minimise the visibility of the guttering. When you have one tank and several downpipes, a dry system will entail having downpipes diverted along walls. It can get ugly, particularly when the tank is also a poor colour choice and the uPVC pipes are not painted. I will get around to doing a separate informative post about wet systems. planeguy Can you comment on the W gutter, versus one downpipe on each end of the gutter - why is that preferred? Similarly, does that mean on the small roofs that will have a single downpipe, does that mean they should have a downpipe in the middle and not the end? The architect won't like the look of that, so what's the purpose? Architects subjugating function for aesthetics is the reason why most display homes don't have downpipes visible from the street view and why downpipes are positioned at the end of walls. Eaves gutters are installed with a slope so that the water will drain efficiently and not pool in the gutter when it stops raining. The minimum slope is 1:500, i.e., 2 mm per metre. The gutter's high points determine the roof areas drained to each downpipe and the low points are where the downpipes are fitted, hence my reference to an elongated W pattern. Preferably, gutters should never be installed with the minimum slope as house settling can later result in the gutters flowing backwards and/or pooling water. A 1:300 slope (3.33mm per metre) should be considered the preferable minimum. Imagine two straight gutters, each 20 metres long. Gutter 1 has the downpipes positioned at the end of the walls as is most common. If the last short length of gutter doesn't slope towards the downpipe as is also common, the water will pool after rainfall but not very much, probable just a few mm but that section will also build up sediment. Decayed organic matter is negatively charged and metal is positively charged. Gutters rust because of contact with sediments, not because they get wet. The tolerances also allow gutters to pool water up to 10 mm deep for 3 days after it rains and so there is no regulatory requirement to slope the last section of gutter. Gutter 1 will have a high point mid way along and allowing for 0.5 metres of guttering between the downpipes and the end caps, the distance between each downpipe and the central high point will be 9.5 metres. If the gutter has the minimum 1:500 slope, the gutter would drop 19 mm to the downpipe but a better 1:300 slope would see almost 32mm of drop and this could be considered unsightly...but you do have a two storey roof. A downpipe at the far end (past the blue roof) also requires more sub surface pipe work because it is further from the tank. Our Gutter 2 example would have two downpipes positioned at 1/4 and 3/4 distance with the high points at the ends and the middle. 5 metres of guttering would flow from either side to the downpipes and a superior 1:250 slope would only result in a 20mm drop between the low and high points. Drainage would be very efficient and the guttering would carry less load. For rainwater harvesting, short gutter runs have more efficient first flush collection. Function Vs aesthetics! planeguy Reading up about tank types, it looks the material choice is fairly even for our use case in metal vs polymer types. Metal 10kl tanks look to be about $300 smaller, but look better. Do you think there is any performance difference? Metal tanks are dearer but they (should) last longer although good poly tanks do last a long time. Metal tanks haven't been without their problems though and there was a (belated) recall several years ago on metal slimline tanks after numerous structural failures. viewtopic.php?f=35&t=74141 Another brand of metal tank leached lead into the water. http://www.examiner.com.au/story/133518 ... ter-tanks/ http://www.dhhs.tas.gov.au/news/2013/le ... ater_tanks There are some good looking poly tanks but avoid the light colours if the tank will receive UV. My main tank is a Clark poly corrugated tank, it looks good and is good. EDIT The post below discusses a very common but very poor roof drainage design that is nevertheless compliant. Gutters overflowing during even medium to light heavy rain is the result. viewtopic.php?p=1289026#p1289026 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Block of two storey townhouses requires painting on the roof. A brick parapet wall separates each unit and extends above the tiled roof. The parapet walls require sealing… 0 3443 That was always going to be a challenge and a test of patience. Full marks to your mate. Did you discuss the wet area near the trampoline? 16 17287 |