Browse Forums Eco Living 1 Apr 30, 2020 2:19 pm Hi all I am looking into rainwater harvesting and have some questions. My questions are: • Is it likely there will be problems with the "wet" set up? I am not sure how much the flow will be affected with charged pipes. • With the "dry" set up, does this usually mean pipes will be run along the walls (a short distance below the eaves/gutters) to the tank? • Is it possible to easily filter and harvest water from hard surfaces such as paving? Thank Re: Rainwater harvesting 2Apr 30, 2020 6:50 pm Hi and welcome to the forum. mini255 • Is it likely there will be problems with the "wet" set up? I am not sure how much the flow will be affected with charged pipes. Rainwater harvesting systems should have all encompassing hydraulic flow calculations done but very few installers/plumbers know how to do this. In fact, if you read through a few of the forum threads, you will also see that many hydraulic engineers also don't know the practicalities such as the affect that mosquito proof mesh has on the flow rate through an overflow outlet. To properly answer your question, I need to know whether it is for a new or existing house as both have different issues. Wet systems divert water from downpipes that are away from the tank, the alternative being to run ugly pipes along walls which is not a good look. A new house will divert the downpipes to the tank and the tank will overflow to the stormwater system. This makes the tank part of the stormwater system and thereby subject to the same compliance Standards. An area frequently found to be in breach of those Standards are water tank overflow pipes that have insufficient overflow capacity to prevent the tank from overtopping during a 1:20 year storm event, the criteria by which eaves gutter compliance is based. Because the downpipes are diverted to the tank, connecting those downpipes to the stormwater system at some later time also means re-plumbing the stormwater system plus the diverted pipes could be under paved/concreted areas. To plumb a wet system at an established house usually means disconnecting the downpipes from the stormwater system and trenching the new pipes to the tank but if the established pipes are used, they will need to slope towards the tank plus capped at some point. A standard wet system pipe needs to rise vertically next to the tank and discharge into the tank's top meshed inlet. This means that a large amount of water is retained in the underground pipes and also the vertical riser and the downpipes to the level of water at the top of the vertical riser. Wet system downpipes should also be fitted with good mosquito proof leaf diverters to prevent organic matter and other pollutants from entering the underground pipe and slowly clogging the pipe and to also prevent mosquitoes breeding. From egg to adult mosquito takes an average 12 days and fitting wet systems with leaf diverters is compulsory in many northern shires. l. If you fit a leaf diverter to a downpipe, you also decrease the available head. mini255 • With the "dry" set up, does this usually mean pipes will be run along the walls (a short distance below the eaves/gutters) to the tank? Usually yes when more than one downpipe is harvested but you could have smaller tanks at each downpipe on a level block and run balance lines between all tanks so that you only required one pump. mini255 • Is it possible to easily filter and harvest water from hard surfaces such as paving? It would have to be done separate to the roof harvesting unless you broke into the stormwater system and had an elevated pump inside a large pit. The pit would have to be regularly cleaned of silt but pumping to a tank with any reasonable velocity requires a large pump plus you have to ensure that the pump didn't cycle and burn out the motor. It would be best to use a dirty water submersible pump and pump to a separate settling tank fitted with level control activation that stopped the pump once the tank filled. Realistically, you are better off concentrating on harvesting the maximum number of downpipes that you can and there are ways to divert the initial dirty roof wash and remove sediment which will improve the quality of water diverted to the tank. 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: Rainwater harvesting 3May 01, 2020 10:29 pm Hello This is for an existing house. In fact, I think some pipes are terracotta (very old and unlikely to be 100% watertight), so there's no way that the existing set up could be converted to a wet system. I was thinking of I could cut in a Maelstrom Filter together with a first flush device just before the pipe reaches the kerb outlet on the street, and install an underground tank. But I am not sure how good the water quality will be (even with first flush). Water quality will especially be an issue because the roof water and hard surface drains are combined at this point. There's no guarantee that the water from the hard surface drains will stay clean after first flush. Maybe a chlorinating device might help with water quality too. Thanks Re: Rainwater harvesting 4May 02, 2020 1:37 pm First flush is the dirty roof wash that needs to be collected straight away at the downpipe, it cannot be collected after it becomes a 'shandy'. Underground tanks are expensive plus it would need an overflow at a suitable height that is large enough to handle the combined rainfall from the roof and the surface drains during heavy rain. Given that you have concerns about the existing pipes, are you only considering harvesting surface water because of concerns about the longevity of using the stormwater pipes? The first step with harvesting rainwater is to determine your intended use and whether that use will be constant all year. You also have to consider how your long term average rainfall pattern will satisfy those needs, for example, are you in a region that has wet and dry seasons? The aim should be to maximise yield and usage to get bang for bucks yet keep costs at a realistic level.. What is your intended use and do you live in a regular rainfall region? Also, what are your downpipe sizes? 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: Rainwater harvesting 5May 02, 2020 7:05 pm Hi Intended use is for watering plants. Maybe later I might have aspirations to connect the toilets for flushing, but I will hold off on this for now because of the work required to run new pipes to the toilets. I am in Sydney, which has decent rain fall. My downpipe sizes are 100x75mm rectangular. I am trying to avoid breaking concrete paths to separately collect roof water, because this will be a lot of work. At the moment, roof water and hard surface drains are combined, and lead to the street kerb. I can tap in easily at a point just before the pipe leads to the street. Thanks Re: Rainwater harvesting 6May 02, 2020 10:40 pm You can easily plumb pumped water to most cisterns without the expense of a mains water switching device, it is a simple and cheap manual system that you can see if you Google "Victorian Building Authority plumbing technical solution sheet 99.01". It has diagrams and explains what can be also found in AS/NZS 3500.3 which the Plumbing Code of Australia (PCA) references. The PCA is Part 3 of the National Construction Code (NCC). Having 100x75mm downpipes indicates good amounts of roof water flowing to each downpipe. Underground tanks are expensive and I can also see sediment issues. If you had a good size above ground tank supplied by a pit/pumped system, the pit would have to be large to avoid the pump frequently cycling plus the pump would obviously need power supplied, would a power supply route create a problem? In this pumped scenario, have you decided where the tank would be sited? If you wanted cleaner water, you could have two tanks and pump water to one tank (a settling tank) that transferred settled water via a balance line to a second tank that supplied the pump. You could also have two or three small diameter tall tanks each filled by their own dry system downpipe. It is usually easy to link tanks and have one pump but a disadvantage would be plumbing three overflow pipes. Are you against having a largish tank next to the house? If acceptable, you could have one downpipe directly fill the tank. If you could see where the gutter's high points are that determine the roof area harvested and if the roof areas considered were on the weather side for maximum yield, you could choose a high yield downpipe and calculate an approximate annual yield. If insufficient for your needs, you could also harvest one or more remote downpipes by having some permanent 32mm or 40mm pipes plumbed at ground level between the remote downpipe(s) and the tank or else just connect an 18mm or 25mm hose between a downpipe and the tank whenever needed. A product I have would be connected to the remote downpipes to enable this and this would almost certainly be the easiest and cheapest option. Advantages include having the water filtered, a first flush provision and overflow pipes not needed. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. 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 6858 18 74561 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 25082 |