Browse Forums General Discussion 1 Mar 14, 2010 11:21 am HI guys I haven't scoured the board fully but I can't see (at a glance) whether there is a better place to post this question, or if in fact it has been asked before... We are looking at installing a water tank/s but I am a bit confused when it comes to determining size. You are advised to calculate based on roof space and rainfall to determine how much rain you could expect to harvest - but - my question is, if the rainwater is usually attached/plumbed to one downpipe, what happens to the rest of the run off from the other downpipes?? Do you essentially only capture the run off from one downpipe or how does it all work? Also, I can work out roof size and rainfall etc, but what guide do I use for how much I actually need/what size to get? We will essentially be using it for garden (3/4 acre block but mostly natives - some lawn), top up the pool as neccessary (very small pool), maybe plumb it into the washing machine and potentially the spare toilet. I don't want to install a 15000l tank if we only need 5000l (making those figures up as I have no clue). Oh, and also, does anyone have a rough idea of how much they cost to get plumbed properly?? Ballpark (just so we can factor it in to the budget). Anyway, if someone could either help me with any of those queries it would be great as I'm just not sure where to start and I want to get the tank installed soon to catch the winter rain. Thanks, Cee Re: General questions re water tanks... 2Mar 14, 2010 1:06 pm Ceebs We are looking at installing a water tank/s but I am a bit confused when it comes to determining size. You are advised to calculate based on roof space and rainfall to determine how much rain you could expect to harvest - but - my question is, if the rainwater is usually attached/plumbed to one downpipe, what happens to the rest of the run off from the other downpipes?? Do you essentially only capture the run off from one downpipe or how does it all work? ask my why but get a bit funny when the washing is left in the rain and I always feel like it needs to be rinsed again. But using rain water to wash the clothes will essentially be the same thing. Is rainwater OK to wash clothes in - isn't it a bit harder or ?????? Funny question but even my DP said same thing when I mentioned plumbing it to the washing machine????? (Copy and paste from your duplicate query so I hope it's the same. Just as well I've been copying my replies because of computer problems, don't know if I could have typed it all out again. ) It depends on the roof. We had space for the tank on one side of the house. One downpipe was already in the ideal position. Another section of guttering flowed away to a downpipe some distance away so the guttering had to be tilted slightly the other way to allow it to be connected to the tank. The roof on the other side of the house does not contribute to the tank, that rainwater still flows into the stormwater system. It seems a shame but it isn't feasible to have another tank of any really worthwhile size on that side of the house, and if there's a way of running piping round to the other side I suspect it would be too complicated and expensive for us to retrofit at this stage. I've heard people who have experience of both say they prefer rainwater to town water. One thing to remember is to get a first flush diverter installed to wash away any accumulated muck from the roof before water starts flowing into your tank. I mentioned it often enough, I don't know how hubby and the installer overlooked it. Re: General questions re water tanks... 3Mar 14, 2010 1:50 pm Our tank is 2750L (all that fits) and is plumbed to our two toilets and regularly runs dry. If you want to use it for all those functions, you're going to need a fair amount of water. You should be able to plumb the tank to two downpipes without too much drama - possibly more, depending on the roof design. You might want to consider two smaller tanks for separate uses, rather than one large one. That way (if you have room) they can be located in two different places and take advantage of different downpipes. You could have one set up for laundry/toilets and the other for garden & pool usage. Re: General questions re water tanks... 4Mar 14, 2010 10:08 pm If you are building with a volume builder they will generaly one plumb 2 or 3 downpipes to the rainwater tank, which means that the majority of the run-off from your roof space literally goes down the drain. We have directed our builder (M3tric0n) to plumb all of our downpipes to the 22500L underground rainwater tank we intend to put in. We would much rather have too much water than not enough. M have charged us $4,205 to do this additional plumbing. Building the Grandview 36 with M$tric0n Plans approved 15/4/2010 Site start date 21/5/2010 Our build thread: viewtopic.php?f=31&t=32825&p=461266#p461266 Re: General questions re water tanks... 7Mar 16, 2010 11:14 am Where do you live Seals? Building the Grandview 36 with M$tric0n Plans approved 15/4/2010 Site start date 21/5/2010 Our build thread: viewtopic.php?f=31&t=32825&p=461266#p461266 Re: General questions re water tanks... 8Mar 16, 2010 4:25 pm Ceebs, Depending on positions, a plumber can run pipes from additional downpipes to your tank. I was asked but didn't request it since there's about 50m2 of roof on the back downpipe - thanks to the not-so-good plumbing in the extension the previous owners did. It cost me about $1200-1300 for 4000L poly tank + delivery + pump + DIY base + electrician for new outdoor power point, and $1000 (incl materials) for my regular plumber to connect roof to tank to pump to 1 tap at tank, 1 tap 10m away, laundry & 2nd toilet a further 5m away. We don't use it for the washing machine (should have got first flush diverter ), rarely on the lawn & toilet, but mostly for the garden (including some exotic plants, herbs & spices). Water fills up the tank fairly quickly on consecutive rainy days and runs out after 4-6 weeks without rain. Oh, and we are in Sydney southwest area. Re: General questions re water tanks... 9Mar 19, 2010 8:56 pm Our builder is charging $9400 for a 3000L slimline above ground rainwater tank. The DA has been approved and the Basix received. As a DA consent condition, council has has asked for a 2000L tank for tapping roof rainwater. Builder is charging $4300 for a seperate 2000L rainwater tank for the roof run off. Dont understand why we need 2 separate rainwater tanks. If we put both the rainwater tanks together, we may have to get the Basix reassessed. Very frustating to know all this now and the pay $13500 for installing rainwater tanks. Re: General questions re water tanks... 11Mar 23, 2010 8:25 am I've had a 10,000L concrete underground water tank installed before the build begins. This is costing me $8,000 and will also add to my 5 star rating. I first asked the builder to quote on the installation and they asked for $16,000. Therefore I did it myself. <START RANT> Water tanks are a complete false economy and an environmental disaster. More energy and wasted money goes into installing individual water tanks at every house that already has connections to our major dams. All that is required is appropriate expenditure by governments on dams and water recycling. Too many people think that dams are a bad thing and that they destroy the environment, however there are sufficient guidelines in place to ensure that any local impacts on habitats etc. are well managed and these local effects are no where near as bad as using brown coal to generate electricity to turn salt water into potable water. </END RANT> View our blog at: http://room4acubby.blogspot.com/ Re: General questions re water tanks... 12Mar 23, 2010 10:25 am room4acubby - Sorry to bust your bubble... Dams are an environmental disaster. Firstly wind will strip between 6-10mm per day via evap, so over a year the water will disappear if not topped up. The water that comes from dams is treated with Chloramine or chlorine... Dams get 'runoff' from all kinds of nasties and has to be treated with the above chemicals to be so-called fit for consumption. But don't put tap water straight into you fish tank or it will kill your fish. I'd go for a tank and we have several... about 200kl of storage. The prices that are being bandyed around here are excessive. A 100kl tank should cost no more than $10,000 including plumbing and a pump. Where you are coming from is where you are going to... Re: General questions re water tanks... 13Mar 23, 2010 11:28 am onc_artisan room4acubby - Sorry to bust your bubble... Dams are an environmental disaster. Firstly wind will strip between 6-10mm per day via evap, so over a year the water will disappear if not topped up. The water that comes from dams is treated with Chloramine or chlorine... Dams get 'runoff' from all kinds of nasties and has to be treated with the above chemicals to be so-called fit for consumption. But don't put tap water straight into you fish tank or it will kill your fish. Onc, I must disagree. There are issues with evaporation, however based on your assessment most major reservoirs would lose less than 5% of their water through evaporation each year as the majority of these dams are at least 60m deep, this assumes no top up. The catchment areas are much larger than the dams themselves making the 6-10mm seem insignificant. Water from dams is treated with more than just chlorine, however I would think that if this treatment did not occur there would be a lot of sick people out there. I do not know what treatments are required for residential water tanks that provide drinking water, but I think these treatments may be just as bad for fish tanks. Dams in Victoria that provide Melbourne with drinking water are all in closed catchments. The run off is well controlled. It does contain "nasties" including droppings and pretty much anything that could find its way on to any residential roof that you are getting the same run off from. View our blog at: http://room4acubby.blogspot.com/ Re: General questions re water tanks... 14Mar 23, 2010 12:19 pm Fair call and far beit for me to want a flame war... but just a simple calculation will tell you that in 1 year 1400mm(average of 3.8mm per day) of evap equates to a lot of water over the 2230 hectares(22,300,000sq mtrs) of dam area in greater Melbourne.. ...about 320,000,000 ltrs of water loss by evap, add to that the loss through fissures in the rock and scouring, it adds up to a LOT. Do we treat our tank water? NO! ...But we do have a filter that is washed 2 or 3 times a year. *The 6-12 mm of evap per day is from BOM W.A. I don't understand how it has been reduced to 3.8mm, but that is the figure of evap history around greater Melbourne. I hope this helps understand why we should all have decent sized water tanks(30kl minimum IMHO[an area of 3mx3mx3m]) Where you are coming from is where you are going to... Re: General questions re water tanks... 15Mar 23, 2010 12:32 pm rupz Our builder is charging $9400 for a 3000L slimline above ground rainwater tank. The DA has been approved and the Basix received. As a DA consent condition, council has has asked for a 2000L tank for tapping roof rainwater. Builder is charging $4300 for a seperate 2000L rainwater tank for the roof run off. Dont understand why we need 2 separate rainwater tanks. If we put both the rainwater tanks together, we may have to get the Basix reassessed. Very frustating to know all this now and the pay $13500 for installing rainwater tanks. OMG that is ridiculously expensive. I got a 2500l tank in for less than 1k. Building on an acre in Macedon ......one day. Re: General questions re water tanks... 16Mar 23, 2010 1:52 pm onc_artisan Fair call and far beit for me to want a flame war... but just a simple calculation will tell you that in 1 year 1400mm(average of 3.8mm per day) of evap equates to a lot of water over the 2230 hectares(22,300,000sq mtrs) of dam area in greater Melbourne.. ...about 320,000,000 ltrs of water loss by evap, add to that the loss through fissures in the rock and scouring, it adds up to a LOT. Do we treat our tank water? NO! ...But we do have a filter that is washed 2 or 3 times a year. *The 6-12 mm of evap per day is from BOM W.A. I don't understand how it has been reduced to 3.8mm, but that is the figure of evap history around greater Melbourne. I hope this helps understand why we should all have decent sized water tanks(30kl minimum IMHO[an area of 3mx3mx3m]) Flame War I'm sorry but I must continue, you have tickled a nerve. OK 320,000,000 ltrs sounds like a lot when we are talking 10,000 litre tanks in peoples back yards. But if you look at the real numbers this is how I see it: 2230 hectares = size of dam area of Thompson Reservoir when full. Assuming all of this area evaporates over a year at 3.8mm per day = 30,930 Mega Litres 1,068,000 Mega Litres = capacity of Thompson when full. Therefore evaporation over a year = 2.9%. The area and volume reduce reasonably linearly, however the evaporation may be up to 5% when the dam is as empty as it currently is. This is not a lot. To look at it another way Melbourne uses about 1000ML of water per day, the Thompson is more than half of Melbourne's total water supply. If 3.8mm evaporates of the Thompson every day this is only 8.5ML which is still only 8.5% of Melbourne's daily usage and again this is assuming that the Thompson is full which it is not. I am glad to know that you do not need any additives to your drinking water. I am still happy drinking my chlorinated water, albeit only mildly in Melbourne. I agree that in areas where the development of large infrastructure dam projects is impractical 30kl tanks is very important, however there are a lot of small residences that can not have such large tanks. The environmental impact of manufacturing all of these tanks and having everyone running electric pumps far outweigh any impacts of a dam. And with all due respect evaporation and chemical additives are irrelevant. View our blog at: http://room4acubby.blogspot.com/ Re: General questions re water tanks... 17Mar 23, 2010 8:57 pm Ceebs, My BIL has a large tank at the rear of his block well away from the house and the down pipes. His plumber placed a small pit around the storm water outlet pipe where all of the roof water runs and in that pit installed a sump pump, with the other end of the pipe from the sump pump appearing at the tank. Thus when it rains the pit begins to fill and so activates the sump pump; if the tank fills a switch is activated at the tank to turn off the pump. I believe there is a general rule of thumb that what ever you spend on the tank you will spend the same amount on all the ancillary plumbing. Re: General questions re water tanks... 18Mar 23, 2010 9:33 pm Don't know how that works... The last tank we put in(4 years ago) was 15,000gal and cost $4800, the plumbing was 5 x 6mtr lengths($12.50each) of 90mm SW pipe and 5 x 90 degree bends ($3.50each) the pump to house was $700(davey) Plumbing was 4 hours digging a tin of blue glue and a hacksaw. Pumping was 20mm pvc pipe 6 mtrs( about $11) and a slab(crownies) for the plumber. Less than $6000 Forget the pit just use gravity, and only pump to the house. Where you are coming from is where you are going to... You should check your detail drawings, it may show downpipe within brick pier. 14 14078 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 17324 |