Browse Forums Building Standards; Getting It Right! Re: Downpipe compliance question- rainwater tank 2Aug 28, 2017 2:06 pm Hi Mars. The following applies. Rainwater harvesting regulations are poorly written and adherence to compliance does not guarantee that a rainwater harvesting system will not be sub standard. Over 95% of the installations that I see fail to meet what I consider to be rainwater harvesting best practice. Rainwater harvesting is covered by the Plumbing Code of Australia (PCA) which is Part 3 of the National Construction Code (NCC). The Building Code of Australia (BCA) is Part 1 & 2 of the NCC and the NCC can be downloaded free of charge. The PCA references different Australian Standards and in doing so, those Standards are legislated. AS/NZS 3500.1 Section 14 Installation Of Water Supply System From Rainwater Tanks states at 14.2 that "All pipes, valves and fittings within a water supply system connected to a rainwater tank shall comply with Section 2." The first two paragraphs of Section 2.3 state... "Materials and products in contact with drinking water shall comply with AS/NZS 4020." "Materials and products to be used for non-drinking water applications shall meet all specifications for pipes except AS/NZS 4020." The PCA also references AS/NZS 3500.3 Stormwater Drainage. Section 2.4.2 Downpipes states... "Materials and products, other than those specified in Clause 2.4.1, used for downpipes shall comply with the following:" "(i) Polyvinyl Chloride (PVC) pipes and fittings as specified in AS/NZS 1254, AS/NZS 1260, AS/NZS 1273, AS/NZS 1477 or AS/NZS 2179.2(Int)." You have stated that your harvested water will be used to flush toilets and for the garden. As such, stormwater PVC which is compliant with AS/NZS 1260 which you will have is approved for use. Note that Drain Waste Vent (DWV) pvc pipe is also manufactured to AS/NZS 1260. Also note that neither PVC stormwater pipe and PVC DWV pipe are pressure rated but PVC DWV pipe is a much stronger pipe. If the Victorian Building Authority (VBA) required DWV pipe to be used for charged rainwater harvesting systems, they should have inserted a variation into the PCA to this effect but they have failed to do so. Other Victorian variations are listed after page 186 in the PCA, you can check for confirmation that the use of DWV pipes in rainwater harvesting charged systems is not listed as a variation. The VBA Technical Solution Sheet (4.05) Charged Systems To Rainwater Tanks that you have linked states on page 2... "NON DRINKING WATER PVC-U at least DWV quality to AS/NZS 1260 PVC-U pipes and fittings for drain, waste and vent application." This technical solution sheet has no legal standing and is only a guide and the very first paragraph states: "The aim of this technical solution is to provide guidance for connecting roof drainage to a rainwater tank, where the tank is either located remotely from the building or where it is not possible to provide a graded downpipe to the tank." The linked VBA document is riddled with misinformation. Consider the following quotes and my appraisals: "STATIC HEAD The minimum distance between the sole of the strainer and rain-head, and the invert of the tank entry is 300mm to provide a sufficient static head on the system." The minimum head requirement for the maximum flow rates through different diameter charged system pipes during high intensity rain events need to be hydraulically calculated. A 300mm head is often not sufficient. "CLEANING AND MAINTENANCE A rain-head and strainer is required at the eaves gutter connection to prevent debris entering and blocking the charged downpipe. While I strongly believe that all charged systems should have rain head leaf diverters fitted to the top of downpipes, they are not required by legislation in Victoria. lf the rainwater tank is to be used for drinking water, then a first flush diverter should also be installed." Note the use of the word "should" which is in keeping with the document's stated aim of being a guide. Unfortunately, I also see vast numbers of first flush diverters fitted to the top of wet system vertical risers which is the inflow pipe that goes up the side of the tank and discharges into the tank's top meshed inlet. The purpose of a first flush diverter is to capture the dirtiest water that is washed from the roof and gutters when it first rains but when the first flush is diverted to a wet system, it falls into the downpipe which pushes the settled water in the vertical riser at the other end into the first flush diverter which fills while the first flush is still in the downpipe! This is not rainwater harvesting best practice! And the Figure 1 diagram irresponsibly states... "Size of overflow equal to size of stormwater charge pipe." The inflow from several downpipes through a charged (wet) system can be well in excess of a tank's overflow pipe's capacity. The mesh on the overflow typically has an open area of little more than 50% and this also needs to be factored in the necessary hydraulic calculations that need to be made when designing a water tank's minimum overflow capacity needed to cope with the inflow during heavy rain. Unfortunately, such calculations are rarely made and water tank manufacturers are not required to state their tank's maximum overflow rate when fitted with a standard overflow outlet. In my opinion, all charged systems should use DWV pipe or u-PVC pressure pipe as I consider the use of SN2 rated 90mm stormwater pipe in charged systems to be substandard as does the VBA but note that 90mm u-PVC 90mm stormwater pipe is also available with a stronger SN4 rating. 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: Downpipe compliance question- rainwater tank 3Aug 29, 2017 7:20 am Thank you Save H2O for such a thorough answer. I will read BCA. My under ground pipes -stormwater - to rain water tank are DWV 100mm. Just the downpipes are 90mm PVC Do you recommend DWV quality downpipes? or just in ground stormwater pipes be DWV? Any specific issues we should be aware of related to 90mm downpipes with charged system other than likely reduced life span compared to DWV downpipes. I have some rain heads but none on the charged downpipes attached directly to the RWT have them . ☺️ (VBA did inform me their guide was not enforceable. Seems ridiculous that plumbing authority doesn't have more say in setting guidelines in Victoria if they feel common practices are not ideal and that fact sheet has misinformation.) Thank you!!!!! Re: Downpipe compliance question- rainwater tank 4Aug 29, 2017 1:54 pm Mars5 I will read BCA. Plumbing regs are in the PCA. Mars5 My under ground pipes -stormwater - to rain water tank are DWV 100mm. Just the downpipes are 90mm PVC Do you recommend DWV quality downpipes? or just in ground stormwater pipes be DWV? Sorry, you did ask about downpipes, I wrongly assumed that all of the pipes would be stormwater. Most builders cheap out and install SN2 u-PVC 90mm stormwater pipes sub surface but your builder hasn't which is good. Now that they are installed, I wouldn't be too fussed about them being 90mm u-PVC stormwater. Water exerts a pressure of 9.81 kPa per metre and this usually won't be an issue provided that the pipes are painted to protect them from going brittle. Most first flush diverters use SN2 90mm u-PVC stormwater pipe and they (usually) have no problems. While u-PVC stormwater pipes are not pressure rated, the pipelines are sometimes subjected to hydrostatic and air pressure leak tests whereby hydrostatic tests usually raise the pipeline pressure by 2-3 metres and usually by 50kPa during air tests. These measures are endorsed by the stormwater pipe manufacturers. SN2 90mm u-PVC is measured as an outside diameter (OD), the actual internal diameter (ID) is 86.2mm whereas the 100mm uPVC DWV pipe has an OD of 110mm and an ID of 104mm. Unless you have specified a style of gutter that you like, you will most probably have the standard 115mm quad guttering and 110mm OD downpipes are not a good fit to this size gutter. u-PVC stormwater pipe is rated by stiffness and there is a minimum stiffness requirement of SN1.5 as required by AS 1260. Nearly all 90mm u-PVC stormwater pipe is manufactured with a SN2 rating but 90mm u-PVC is also made as SN4 which has thicker walls which reduces the ID from 86.2mm to 85mm. The reduction in ID is no problem as the pipe still has about 13% greater volume than a standard 100mm x 50mm downpipe. If the VBA and other State plumbing regulatory bodies were credible, they would introduce a variation into the PCA that mandated the use of SN4 uPVC 90mm stormwater pipe or DWV pipes for downpipes and subsurface pipes for charged systems. Mars5 I have some rain heads but none on the charged downpipes attached directly to the RWT have them . ☺️ Unfiltered charged systems will clog up in time if they can't be properly flushed. The only rainhead leaf diverter that I recommend is the ICON Leaf and Debris Controller because it has an outer screen that actually does flush debris from its surface...unlike many others that have given leaf diverters a bad name. I will soon be selling a kit that includes the ICON diverter plus a low yield loss 100mm first flush diverter kit (with an adapter to fit to 90mm u-PVC stormwater pipe plus postage for less cost than you can buy a 100mm first flush diverter for at the big green shed. It is just a matter of finding the time to introduce it at the moment. Mars5 (VBA did inform me their guide was not enforceable. Seems ridiculous that plumbing authority doesn't have more say in setting guidelines in Victoria if they feel common practices are not ideal and that fact sheet has misinformation.) At least you spoke to someone who knew how the regulations work. Australian building and plumbing regulations are a mix of the BCA, Australian Standards which the BCA regulations have hierarchy over, performance based solutions that only require one expert’s signature to certify and which can then override a manufacturer’s expert opinion, deregulation that puts trust in some not worthy of trust, self certification that allows substandard work to pass unchecked plus State and local council variations that are often un-knowledgeable and erroneous and for which there is no appeal even when they conflict with the NCC's premise of being performance based. Throw non regulatory Guides that contain non regulatory and erroneous information into the mix and you end up with a cacophony that addles the reasoning of most reasonable people including some experts and also allows for unsatisfactory outcomes. Given the poor 'information in the VBA Technical Solution Sheet 4.05 that many would believe to be based on applicable regulations, would you have confidence in the VBA exercising greater control of the regulatory framework? Some other States have introduced overriding variations and regulations in the past that haven't even deserved amateur status. For example: The Brisbane City Council (BCC) introduced a regulation that mandated suburban rainwater tanks had to harvest a roof area of 100 sq m or 50% of the roof area, whichever was the greater. The trouble was that it never occurred to them to mandate for the tank's overflow to be hydraulically designed to be greater than the inflow capacity during a 1:20 Average Recurrence Interval (ARI). During a 1:20 ARI for which eaves gutter and downpipe compliance is based, the Brisbane 5 minute average rain intensity duration on which the 1:20 ARI is based is about 4mm per minute! The South Australian government introduced a variation into the PCA that mandated suburban rainwater tanks connected to the house to have automatic mains water switching devices which means that substantially cheaper bullet proof manual mains water switching devices cannot be legally fitted as an option. 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: Downpipe compliance question- rainwater tank 5Sep 01, 2017 8:14 pm SaveH2O Given the poor 'information in the VBA Technical Solution Sheet 4.05 that many would believe to be based on applicable regulations, would you have confidence in the VBA exercising greater control of the regulatory framework? Thank you SaveH20 for all the detailed information. Widths of pipes and pressure exertion.... etc Much more than the builder and his plumber ... or VBA have been able to provide when i have asked the same question of them several times. You are of course correct re: gutters. The builder did say that the 90mm downpipes were used match the gutters but could not explain more when I asked if they could withstand water pressure of charged system etc. Maybe I'll add to thread - things "I wish I knew to ask about/check before building" - gutters, rainheads, downpipes, inspection points in downpipes....... And yes re: your comment about VBA. Good point. A sad state of affairs. Downpipe compliance question- rainwater tank 6Sep 01, 2017 8:17 pm SaveH2O The only rainhead leaf diverter that I recommend is the ICON Leaf and Debris Controller Also as I don't have the computer skills to put both your quotes in the same reply - Is it possible at some time in the future for me to have a rainhead leaf diverter like the one you suggested above retrofitted ............... with the gutters and 90mm down pipes I have that currently have no rainhead ?. If yes, please do PM details once you introduce it for sale.... any recommendations on plumber to install in Melbourne also welcome. Re: Downpipe compliance question- rainwater tank 7Sep 03, 2017 10:01 pm You can buy the ICON diverter in Bunnings for $38 but I intend to also supply them separate to the kit I mentioned and post free at the same price in the Melbourne metro area. I will PM you soon. A big mistake that people make is to fit leaf diverters unnecessarily high. All leaf diverters need maintenance and safe access is important. Because the ICON diverter's outer filter now has a steep sloped non wire mesh straight surface that doesn't trap debris, it is low maintenance but there is an inner mosquito proof wire mesh filter that does require occasional close up inspection. Fortunately, the outer filter lifts up on two pivots and inspection is very easy. I know a good plumber who has a passion for rainwater harvesting but he is in the outer SE suburbs. I can't recommend a lot of plumbers I come in contact with. The photos below show what happens when a leaf diverter retains water or doesn't flush debris. Sorry about the poor quality of the first photo. I also don't recommend the 'bucket' type of leaf trap (they have an inner mesh filter), the bottom photos might give you a laugh. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ As an aside, when a downpipe is sloped towards the wall, the water that flows along the (inside) bottom of the near horizontal pipe transitions to flow down the pipe's inside edge that is the furthest away from the wall. Guess where most of the water falls? 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: Downpipe compliance question- rainwater tank 8Sep 13, 2017 9:14 pm SaveH2O You can buy the ICON diverter in Bunnings for $38 but I intend to also supply them separate to the kit I mentioned and post free at the same price in the Melbourne metro area. I will PM you soon. . Guess where most of the water falls? Thank you. I've had phone problems so just logged back on. That would be really helpful to have your PM when you are selling. I'm in south east, so might be in plumber's range. Would be great to get advice on what is possible at this stage. Yikes re: types of sloppy work you see. Houses like white goods don't seem be made to last anymore Re: Downpipe compliance question- rainwater tank 9Sep 13, 2017 9:25 pm Mars5 Houses like white goods don't seem be made to last anymore I'm in south east, so might be in plumber's range. Project homes are like sausages...if you saw how they were made, you wouldn't eat them. He is at Upwey but he ranges like most plumbers do. I'll send you a PM, just been very busy lately. 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: Downpipe compliance question- rainwater tank 11Nov 07, 2018 6:53 pm No such thing. 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: Downpipe compliance question- rainwater tank 12Nov 07, 2018 10:48 pm Well in an article (2016) the NCC mentioned that to achieve a 6 star standard rating there must be provided a minimum 2000litre rainwater tank (+other specs). How do you cite that in a drawing? The article https://www.nationalpolyindustries.com. ... australia/ This link for Victorian 6 star achievements notes! https://www.google.com.au/url?sa=t&sour ... 1593928881 I get this requirements where are they specified: "Buildings will need to be designed to ensure that roof water from a minimum of 50 square metres of roof catchment area is: collected by a drainage system (gutters and downpipes); and stored in a minimum 1000 litre rainwater tank; [I need the standard cited, what regulation?; is it relevant to BCA standard?] and is plumbed to at least a toilet or water heater or all laundry cold water outlets." Sustainable Design Requirements For New Houses, House Extensions & Transportable Buildings Development Guide No. 19 Any help welcomed! Cheers Re: Downpipe compliance question- rainwater tank 13Nov 08, 2018 6:04 am The requirement and regulations for rainwater tanks varies between states and even regions within States. Your situation depends on where you live and sometimes your council wikll have over-rides. There is not a one all-encompassing rule and not all States require water tanks on new homes. The 2,000 L tank servicing a minimum 50 sq m roof catchment area is a Victorian 6 star requirement (are you in Victoria?) but a tank is not required if you specify a gas boosted solar HWS or when the property is connected to recycled water...water that you are charged for. "Roof catchment" is deemed to be the roof area as looked at as a flat plan area but factored for the slope by using a multiplier found in AS/NZS 3500.3 which allows for wind driven rain. For example, the common 22.5 degree roof slope is factored as 1.21 which would give a plan area of 40 sq m draining to one downpipe a factored or roof catchment area of 48.4 sq m. In this situation, two downpipes would be required. Note that a standard Victorian slotted 115mm quad gutter would not be compliant to drain a 48.4 sq m roof catchment area in any case. NSW is bound to BASIX. South Australia has a tiny 1,000 L mininum tank capacity requirement and they don't allow the use of manual switching devices! This variation is found in the NCC. The tank size is also dictated by local council rules which may include a detention requirement. In these cases, the tanks can be very large. Different State variations are found in the NCC but local councils can override national regulations and these mandates do not appear in the NCC. Your builder should know the local council overrides if any. The BCC minimum roof area harvested mandate I mentioned earlier is one example. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. 18 90480 DIY, Home Maintenance & Repair But if it is a ground level open pit, then it is not a charged system. No surprises there. The pipes have obviously been altered and there would be a reason for this.… 3 31280 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 31154 |