Browse Forums General Discussion Re: Drainage Point in a Charged System 2Jan 25, 2021 10:57 pm There is no regulatory requirement to have a pit on a wet system. It is also a folly to have a pit that can't drain because it will quickly flood. The purpose of the silt pit is to catch the crud built up in the wet system sump when drained to prevent the crud entering the stormwater system. They also state that a drainage pipe can be extented to a low point on the property to allow the wet system to drain (or words to that effect). This is fairly simple advice and wet system sumps do need draining to clear built up crud. Best practice however is to install a sediment trap to a non turbulent section of pipe between the downpipes and the tank. This will constantly capture the bed load (settled sediments), preventing it from entering the tank. Flushing is also more effective and there is much less yield loss. These simple sediment traps have been fitted all over the world now. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ 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: Drainage Point in a Charged System 3Jan 26, 2021 9:34 am SaveH2O There is no regulatory requirement to have a pit on a wet system. It is also a folly to have a pit that can't drain because it will quickly flood. The purpose of the silt pit is to catch the crud built up in the wet system sump when drained to prevent the crud entering the stormwater system. They also state that a drainage pipe can be extented to a low point on the property to allow the wet system to drain (or words to that effect). This is fairly simple advice and wet system sumps do need draining to clear built up crud. Best practice however is to install a sediment trap to a non turbulent section of pipe between the downpipes and the tank. This will constantly capture the bed load (settled sediments), preventing it from entering the tank. Flushing is also more effective and there is much less yield loss. These simple sediment traps have been fitted all over the world now. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Thanks for your reply. Is there a regulatory requirement to have a sediment trap? Is it only required if you're going to drink the tank water? Or is it good practice regardless? Where does the 40mm DWV pipe connect to? ie. Where is the sediment disposed? I can see that the sediment would drop down into the 45 degree bend then travel through the 40mm pipe. But where does it go from there? Re: Drainage Point in a Charged System 4Jan 26, 2021 2:48 pm Lisa06 Is there a regulatory requirement to have a sediment trap? No, it is simply best practice to prevent bed load from building up in the sub surface pipe and also entering the tank during heavy rain when increased velocity allows debris to be carried up the vertical riser. The trap is just a carryover from our Supadiverta development program to capture fine bed load. Even though the Supadiverta uses a 0.75 mm filter, it was surprising how much small sediment still made its way through the filter and settled as bed load and so it was obvious how beneficial it would be if also fitted to a standard wet system. Lisa06 Is it only required if you're going to drink the tank water? Or is it good practice regardless? Good practice prevents sediment building up in the tank, only fine suspended particles that look like a fine covering of talcum powder on the tank's floor enter the tank. Water quality is improved and the usual tank cleaning requirement can be extended by many years plus cleaning is super quick and simple. Just to explain, water travels through a non turbulent section of flooded pipe in boundary layers (aka streamlines), the water in the core travels fastest and the water on the wall is mostly stationary. Because of this phenomenon, the bed load doesn't get 'pushed' to the bottom of the vertical riser but builds up in small colonies in non turbulent sections along the entire wet system pipe. In time, these small colonies become larger and merge, becoming difficult to completely flush once additional bacterial die off combines to create a black resinous tar like substance. This substance will be well known to anyone who has tried to clean a dirty empty tank. I have linked (below) a Homeone thread's 12 month summary of a QLD rainwater harvesting system that used sediment traps. The property owner actually drew the sediment trap diagram for me! viewtopic.php?p=1146540#p1146540 And another who also installed one. viewtopic.php?p=1551215#p1551215 Lisa06 Where does the 40mm DWV pipe connect to? ie. Where is the sediment disposed? I can see that the sediment would drop down into the 45 degree bend then travel through the 40mm pipe. But where does it go from there? Anywhere you like, even to a short standing outlet. The pipe can be any size but reducing from 100mm DWV to 40mm DWV minimises yield loss while increasing the flush velocity.The elbow and decrease in size also generates turbulence which aids cleaning. 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: Drainage Point in a Charged System 5Jan 26, 2021 7:18 pm SaveH2O Lisa06 Is there a regulatory requirement to have a sediment trap? No, it is simply best practice to prevent bed load from building up in the sub surface pipe and also entering the tank during heavy rain when increased velocity allows debris to be carried up the vertical riser. The trap is just a carryover from our Supadiverta development program to capture fine bed load. Even though the Supadiverta uses a 0.75 mm filter, it was surprising how much small sediment still made its way through the filter and settled as bed load and so it was obvious how beneficial it would be if also fitted to a standard wet system. Lisa06 Is it only required if you're going to drink the tank water? Or is it good practice regardless? Good practice prevents sediment building up in the tank, only fine suspended particles that look like a fine covering of talcum powder on the tank's floor enter the tank. Water quality is improved and the usual tank cleaning requirement can be extended by many years plus cleaning is super quick and simple. Just to explain, water travels through a non turbulent section of flooded pipe in boundary layers (aka streamlines), the water in the core travels fastest and the water on the wall is mostly stationary. Because of this phenomenon, the bed load doesn't get 'pushed' to the bottom of the vertical riser but builds up in small colonies in non turbulent sections along the entire wet system pipe. In time, these small colonies become larger and merge, becoming difficult to completely flush once additional bacterial die off combines to create a black resinous tar like substance. This substance will be well known to anyone who has tried to clean a dirty empty tank. I have linked (below) a Homeone thread's 12 month summary of a QLD rainwater harvesting system that used sediment traps. The property owner actually drew the sediment trap diagram for me! viewtopic.php?p=1146540#p1146540 And another who also installed one. viewtopic.php?p=1551215#p1551215 Lisa06 Where does the 40mm DWV pipe connect to? ie. Where is the sediment disposed? I can see that the sediment would drop down into the 45 degree bend then travel through the 40mm pipe. But where does it go from there? Anywhere you like, even to a short standing outlet. The pipe can be any size but reducing from 100mm DWV to 40mm DWV minimises yield loss while increasing the flush velocity.The elbow and decrease in size also generates turbulence which aids cleaning. Thank you for explaining how the tar-like substance develops -that makes a lot of sense. What do you mean by non-turbulent sections? Which sections of a wet system pipe are non-turbulent? Thank you for those links -I have read them before but will read them again. I read in one of your links that you can only reduce the pipe size if you have leaf diverters fitted. We don’t actually have them fitted (we are the second owners and they were never installed) and there is no room to actually fit them (not enough head). So does that mean we can’t fit a sediment trap? Also, what exactly is a purge valve? Is it different to a sliding gate valve? The sediment trap picture you shared doesn’t have a drainage pit, and I understand you said that it would flood quickly so it’s not the best idea. If that's the case, then how will it be possible to drain the charged system (if it's necessary)? I have another unrelated question for you, please… if the overflow mesh on a water tank is removed, can the overflow be connected directly to the LPOD without installation of an airgap? Is an airgap a regulatory requirement or just best practice? Thank you. Re: Drainage Point in a Charged System 6Jan 26, 2021 8:56 pm Lisa06 What do you mean by non-turbulent sections? Which sections of a wet system pipe are non-turbulent? Water flow is either laminar or turbulent. Water entering a wet system from a downpipe creates turbulence because of the two different flow paths colliding. An elbow creates turbulence due to induced boundary layer velocity variance causing eddies and vortices to form. It is best to fit a sediment trap 4-5 metres past the last area of turbulence. Lisa06 I read in one of your links that you can only reduce the pipe size if you have leaf diverters fitted. We don’t actually have them fitted (we are the second owners and they were never installed) and there is no room to actually fit them (not enough head). So does that mean we can’t fit a sediment trap? Just use a discharge pipe size that will pass an object that will fit down the downpipe. The object could be a kid's toy or anything. The pipe needn't be very long and there will be plenty of water in the downpipes and riser to provide an adequate flushing head. Lisa06 Also, what exactly is a purge valve? Is it different to a sliding gate valve? Any suitable outlet valve will do. Names vary throughout Australia. Lisa06 The sediment trap picture you shared doesn’t have a drainage pit, and I understand you said that it would flood quickly so it’s not the best idea. If that's the case, then how will it be possible to drain the charged system (if it's necessary)? It is buried. the valve is on the end of the pipe. Lisa06 … if the overflow mesh on a water tank is removed, can the overflow be connected directly to the LPOD without installation of an airgap? Is an airgap a regulatory requirement or just best practice? The overflow pipe should be meshed either at the outlet (inefficient) or with the air gap product or similar fitting. The mesh is to prevent pests like rats and frogs from entering the tank. Rainwater tank regulations have never been adequately written and there are also health regulations to abide by but which are inadequately publicised. Councils also put in their 2 cents at times and often they are not worth even that. The regulations are a hodgepodge of inadequacy, misinformation and localised variables of often questionable value. I think that QLD mandates the use of an air gap to protect the tank water from surcharge should the stormwater system become overloaded. I don't know offhand whether you would be required to have the overflow pipe meshed but I recommend that you do. 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: Drainage Point in a Charged System 7Jan 29, 2021 1:38 pm SaveH2O Lisa06 What do you mean by non-turbulent sections? Which sections of a wet system pipe are non-turbulent? Water flow is either laminar or turbulent. Water entering a wet system from a downpipe creates turbulence because of the two different flow paths colliding. An elbow creates turbulence due to induced boundary layer velocity variance causing eddies and vortices to form. It is best to fit a sediment trap 4-5 metres past the last area of turbulence. Lisa06 I read in one of your links that you can only reduce the pipe size if you have leaf diverters fitted. We don’t actually have them fitted (we are the second owners and they were never installed) and there is no room to actually fit them (not enough head). So does that mean we can’t fit a sediment trap? Just use a discharge pipe size that will pass an object that will fit down the downpipe. The object could be a kid's toy or anything. The pipe needn't be very long and there will be plenty of water in the downpipes and riser to provide an adequate flushing head. Lisa06 Also, what exactly is a purge valve? Is it different to a sliding gate valve? Any suitable outlet valve will do. Names vary throughout Australia. Lisa06 The sediment trap picture you shared doesn’t have a drainage pit, and I understand you said that it would flood quickly so it’s not the best idea. If that's the case, then how will it be possible to drain the charged system (if it's necessary)? It is buried. the valve is on the end of the pipe. Lisa06 … if the overflow mesh on a water tank is removed, can the overflow be connected directly to the LPOD without installation of an airgap? Is an airgap a regulatory requirement or just best practice? The overflow pipe should be meshed either at the outlet (inefficient) or with the air gap product or similar fitting. The mesh is to prevent pests like rats and frogs from entering the tank. Rainwater tank regulations have never been adequately written and there are also health regulations to abide by but which are inadequately publicised. Councils also put in their 2 cents at times and often they are not worth even that. The regulations are a hodgepodge of inadequacy, misinformation and localised variables of often questionable value. I think that QLD mandates the use of an air gap to protect the tank water from surcharge should the stormwater system become overloaded. I don't know offhand whether you would be required to have the overflow pipe meshed but I recommend that you do. Thank you for your very clear explanations. They make perfect sense and are very helpful. Re: Drainage Point in a Charged System 9Nov 07, 2021 1:02 pm Lisa06 @SaveH2O I have another question for you, please... The pipe from the tank overflow to the LPOD (which will be approx 30m in length) -does it need to have bedding (ie. crushed rock) underneath it like the stormwater pipes do? Thanks. Just saw this query. Better late than never to reply I guess. The pipe between the tank's overflow outlet and the LPOD is part of the stormwater system and those regulations apply. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Once you know the basics, the rest is easy. Read my post in the thread linked below. viewtopic.php?p=1919271#p1919271 2 19517 2 2525 Building Standards; Getting It Right! Hi All, We have a fall from road to garage front. But we cannot put a drain/grate because no discharge point put by the builder. Now they complain not enough space for… 0 9242 |