Browse Forums Building Standards; Getting It Right! 1 Aug 01, 2011 10:32 am Hi, We have finished building our house and are currently living it it. Have been for about 6 months. Due to new Basix laws we have a 4500L water tank which is plummed to our toilets and washing machine. There is 2 problems with this. 1. There is no first flush or diverter/filter on the lines heading to the water tank. We live in Muswellbrook which is a mining town therefore we get a lot of dust settling on our roof. This means when it rains dust flows ionto the tank and into our toilets etc. It also make the water smell and for a while we had to get our washing done else where. 2. The water tank has every single down pipe from the roof going into it (house is 316ms surface area so a fair bit of water when it rains). The overflow is also 90mm down pipe so there are 2 90mm outlets in and 1 90mm outlet out for Over flow. When we get decent rain the overflow cant cope and water pours out the overflow. I suppose what I am asking is there a standard for filtering the water and also shouldnt there be a ratio of water in/out to teh tank? The waste should at least be 100mm right. Also there is no drainage at the front of our house (we have cut 1.2m). Is the drainage from yard run off our task or the builders? Any heklp would be appreciated. Re: Water Tank Problems 2Aug 01, 2011 11:17 am There is no real standard for filtering of tank water its generally up the user to decide what they need. What you probably need although its more money is a tank that the water flows in before the main tank this tank should then have a pipe connecting the two tanks at a high level. Most of the material will then settle out in the first tank which you can drain to waste occasionally. The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Water Tank Problems 3Aug 08, 2011 2:50 pm The builder is responsible for drainage during construction, so even if drainage is not specified as part of the finished house, you should have been left with at least some kind of makeshift drainage that keeps water from pooling against the house. Our contract specifies that land must fall away from the house, which the builder did NOT do. It doesn't specify for what distance it has to fall away from the house though. My approach was to fix the drainage myself, but I've made it clear to my builder that I'm aware that they did not handle drainage during construction, and that I have kept evidence in case there are any issues later on. I am pretty sure that water pooling against the house (and also water pooling on any tiled area) is a defect, though I don't recall where I read that. Metricon Riva 33 - http://herlihy-riva.blogspot.com Site start 15/03/2010 - Handover 23/12/2010 9 months and 8 days (284 calendar days) from site start to handover Re: Water Tank Problems 4Aug 11, 2011 2:49 pm Btherl, BCA regulations state that the ground must have a 1:20 fall for the first metre away from your house to prevent water pooling. Dangerjim, Your roof water harvesting & tank set up is sub standard for a number of reasons. You have a 'wet' system fed by 2 wet (charged) 90 mm PVCu pipes fed from 316 sq m of roof. I don't know your area's 1:20 Average Recurrence Interval (ARI) and you should find out what it is. Your area's 1:20 ARI determines your eaves guttering and downpipe size and the number of downpipes needed for the maximum roof areas that each downpipe can drain. Let me guesstimate that your area's 1:20 ARI is 180 mm an hour. The ARI is actually worked out over a 5 minute interval; in the case of our example, this is 3 mm of rain a minute OR 948 litres a minute falling on your 316 sq m roof (1 mm on 1 sq m = 1 litre). For compliance in our example, you would most probably need ten 90 mm downpipes. Remember, this is an example given that I don't know your 1:20 ARI. If you have less than ten 90 mm round downpipes, you may also have a non compliance roof drainage issue. As you would know, the 2 X 90 mm downpipes feeding the tank run full of water whereas downpipes discharging to stormwater never hold less than two thirds air unless there is a restriction. The tank's overflow pipe however does not flow with a charged head and will not drain the 948 litres per minute as in our example, in fact, it would struggle to drain much more than 200 litres per minute for several reasons including the fact that the overflow outlet should be fitted with a flow restricting low % open area mosquito proof mesh. EDIT 27/08/2013; There is a water tank syphonic base overflow system now available that vacuums the entire tank floor at 9 litres per second (540 litres per minute) through an 80 mm DWV pipe. An air break at the top of the overflow pipe inside the tank prevents the tank syphoning lower than the bottom of the tank's overflow outlet. By syphoning water off the bottom of the tank, sediment and the worst quality water from the anaerobic zone is discharged to waste. The tank's mitigation capacity (between the overflow pipe and the top of the meshed inlet) also assists during heavy downpours. An Australian website is not up yet and until it is, I can provide the Australian contact if requested. http://www.youtube.com/watch?v=e1_B9WITe94 The common use 90 mm PVCu stormwater pipe has less than a 2 mm wall thickness, is flimsy and is not pressure rated. As such, it is unsuitable for use as a wet system transfer pipe. The head charging the two infeed pipes would need to be hydraulically calculated to ensure that they can handle the flow transfer from your roof during a 1:20 ARI. At any rate, 100 mm DWV pipe (3 mm thick walls and 104 mm internal diameter) and not 90 mm PVCu stormwater pipe with an internal diameter of 86.2 mm should have been used for the wet system. Water tank overflow regulations are generally very poorly written or non existent. Some councils, for example the Brisbane City Council, also mandate minimum roof areas that need to be harvested but fail to consider that the tank overflow needs to be equal to or greater than the inflow capacity in order to prevent the tank over topping during a major storm. Many regions require mosquito proofing (leaf diverters) for wet systems. This is because the pipe work, unless drained after every rain event, remains full of water to the level of the bottom of the infeed pipe above the tank's top meshed inlet. The discharge end of the pipe will also require a flap to prevent mosquitoes entering the pipe and breeding. Leaf diverters reduce the available head and it is common for wet systems to be plumbed with an insufficient head to transfer water during a major storm. Many leaf filters are rubbish; certainly don't get ones that have a coarse outer mesh (generally 6-8 mm) and a fine inner mesh. These allow a lot of contaminants,for example bird droppings, to fall through the outer mesh and then wash through the finer inner mesh. Most debris is also washed from the roof and gutters during storm events and this can cause this design to block and overflow. They also need regular maintenance and climbing ladders can be hazardous. The new Leaf Eater Advanced has a fine outer mesh and is much better although there is still room for improvement. If you don't have first flush diverters, you should fit them but don't fit a first flush diverter to the top of the tank's vertical riser. All this will do is drain off the water that has settled in the riser since the last rain while the first flush is still in the downpipe at the other end. Always fit them to the downpipe. A 100 mm first flush diverter has over 40% more volume than one that uses a 90 mm stormwater pipe. Re your water smelling, this is probably due to the water stagnating within the wet system pipe work. As the trapped organic matter breaks down, the water becomes anaerobic (devoid of oxygen) and then pollutes the tank water the next time it rains. Totally agree with bashworth re having a settling tank. The tank (with the decanted water) connected to the pump is best being a smaller tank but one that is of equal height to the larger tank. Also, unless you want your pump ingesting sludge and drawing the worst quality water in the tank, have the pump's draw off valve fitted a minimum 100 mm above the bottom of the tank. You could also consider buying a large (+100 litres) stand alone pressure tank supplied by the pump. This will eliminate about 90% of the pump start ups, eliminate water hammer to the washing machine and reduce energy use. Copper pipe is also best NOT USED with rainwater as rainwater is naturally acidic. The people who have installed your tank are probably no worse than most in the industry. Most of the tank installations I see are sub standard and there is a high incidence of non compliance. 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 Tank Problems 5Aug 11, 2011 3:24 pm Jim this may be to late but can your builder fit another washing machine tap which is supplied from the mains? The plumber here fitted three taps for the washing machine...hot and cold are mains, then the third is rainwater (cold), his reasoning was that if the rainwater tank is empty then you just turn on the mains hot/cold water to do a load of washing. He also, (unlike me) seems to think rainwater is inferior, whereas I've lived on acres where rainwater was the 'only' water available so I'm used to dealing with a whole of house rainwater system. Because I always wash in cold water (only using hot water if I'm dyeing fabric) I attached the washing machine 'cold' inlet hose to the rainwater tap...then the washing machine 'hot' inlet hose to the cold mains tap, because there are only two inlets into the washing machine this I thought was the simplest and easiest way. If I want to fill the washing machine with mains cold water, I just select 'hot' on the washing machine. When I want to do a hot wash, or dye fabric, it's a simple matter of unscrewing the hot inlet hose from the cold mains tap and screw it onto the hot mains tap. I know this sounds a bit confusing at first but it's really very simple and gives me the best of both worlds...not that I think I'll ever run out of rainwater because I'm on the coast from you where even a light shower or heavy dew during the night tops up the tanks but having said that I don't have the dust problem which I know is a problem in your area. My one complaint with the setup here is that the plumber wouldn't put a tap at the bottom of the rainwater tank so in the event there is some dirty water or I simply want to flush the tank, it's a simple matter of turning the tap...but that's on their bucket list anyway. Only one side of the roof goes into the rainwater tank, the rest goes to the soakwell along with the overflow from the tank. H2O....I've noticed the overflow here is only one 90mm pipe whereas 4 x downpipes feed the system. LOL Haven't ventured out when it's raining but it gurgles quite a lot. Re: Water Tank Problems 6Aug 11, 2011 3:40 pm HappyCamper, The gurgling has a fairly complicated explanation that involves the tank's air gap above the outlet and the dynamics of what happens when the water rises above the outlet and loses the annular vortex that is necessary to maintain gravity/weir flow. Googling Syphonic Pulse might bring something up. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. If you can calculate the reasonable charged head from let's say 100mm below the gutter to the top of where the vertical riser's horizontal discharge pipe will be, that… 11 17991 Building Standards; Getting It Right! Thank you for the generous offer. I need to get the plumber out to give me an explanation. As mentioned I haven't seen any rain water discharge from pipes 1& 3. It… 7 11326 Can a plumber put a tap on a rain water tank which is full? Tank is similar to one in photo. Cheers. 0 1976 |