Pete Posted May 15, 2017 Share Posted May 15, 2017 How many people have bothered with rainwater harvesting? We will be mostly be two adults after September so just wondering if it is worth investing in this facility or just paying for what we use through the water meter. The system we have been looking at costs about £2000 plus associated pipework (fitting by myself) so quite a considerable payback time. TIA Link to comment Share on other sites More sharing options...
reddal Posted May 15, 2017 Share Posted May 15, 2017 We looked at rainwater harvesting - but in the end we built our own spring water supply with a borehole and rainwater harvesting on top of that seemed overkill. I fear neither solution is easy to justify on pure economic grounds if you have mains water available - so it depends how much you are willing to pay for more eco cred. - reddal Link to comment Share on other sites More sharing options...
Dudda Posted May 15, 2017 Share Posted May 15, 2017 I’ve a cold water manifold feeding all cold supply (basins, showers, bath, etc) and plumbed an additional rainwater manifold which feeds the toilets and an outside tap. Currently this manifold is fed by the mains water the same as the cold water manifold. I couldn’t justify the expense of a tank and pump currently but did the internal plumbing which was relatively cheap and I wouldn’t be able to do easily later. It was just an additional manifold instead of a larger cold water one, a small bit of extra pipe and an additional duct to outside. I also relocated some rain water runs outside from the downpipes to allow for the future rainwater tank as it was no additional expense now but would be in the future. Link to comment Share on other sites More sharing options...
PeterW Posted May 15, 2017 Share Posted May 15, 2017 4 hours ago, Pete said: How many people have bothered with rainwater harvesting? We will be mostly be two adults after September so just wondering if it is worth investing in this facility or just paying for what we use through the water meter. The system we have been looking at costs about £2000 plus associated pipework (fitting by myself) so quite a considerable payback time. TIA On that cost it's a "never pay back" unless you've got an allotment garden ..! mine is coming in at around £350 for all the bits for 2900 litres of storage and pumps / filters. Only difference on internal pipe work is that I have a dedicated 22mm feed from one end of the house to the other with the toilets tee'd from it and it will end at an outside tap. Deciding whether to run the washing machine currently. Link to comment Share on other sites More sharing options...
vivienz Posted February 10, 2018 Share Posted February 10, 2018 I'm bumping this thread as it's something I'm looking at for the new build. I want to collect rainwater from the house for use in the garden, so it doesn't need to be potable and doesn't need to be plumbed into the internal supply of the house. I'd like the tank to be buried and large - we have water butts everywhere we can at our current place and these soon run dry in the summer, and our garden isn't that big right now. As I'd like the storage underground, though, I will need an electric pump to extract the water for use. It's likely that we will only need to draw substantially on the supply through late spring to late autumn - would leaving the system, including the pump, alone for this length of time cause problems? Presumably, just running it periodically could avoid any difficulties this may cause. Also, the pump would need to be housed outside - would there be problems with this? I've had a look at different systems available and for large volume collection, they all seem to assume that the water will be used in the house for flushing loos & washing machines, etc. Is there any system in particular that's worth looking at, as far as anyone knows? Prices also seem to vary a lot, but often with many more bells and whistles than I anticipate needing for our use. Any hints or tips would be much appreciated! Link to comment Share on other sites More sharing options...
Ferdinand Posted February 10, 2018 Share Posted February 10, 2018 What does large mean for your tank? Is there an approximate number in cubic metres? Link to comment Share on other sites More sharing options...
Bitpipe Posted February 10, 2018 Share Posted February 10, 2018 I did a DIY system for under £200 (excluding pump) using IBCs, however these are not suitable for burying underground. Its' surprising how quickly a 4000l system will fill in heavy rain and how quickly you can deplete it. Average hosepipe will use 1000 l per hour. Link to comment Share on other sites More sharing options...
Pocster Posted February 10, 2018 Share Posted February 10, 2018 I’m going to install it and yes at 2k return on investment will be sometime but that is based on water costs *today* . You use more than you think and as just 2 adults could skip it . But hey ! Awkward to retro fit and helps save the plant a tiny tiny bit . I’d pay for this, AShp , pv , pv battery etc . Anything to get off grid as much as possible . I guess if cost is the issue then at least put the pipe work in ready for a harvesting tank at a later date . But as a self build I always take the 20% vat back ( discount ) as a once in a lifetime offer . Call them up and haggle the price down ! This works surprisingly often on the premis you will pay now over the phone . its a simple technology ( tank and pump ) ; take the opportunity while you can would be my advice ? Link to comment Share on other sites More sharing options...
vivienz Posted February 10, 2018 Share Posted February 10, 2018 In terms of size, I've looked at some Met Office figures for rainfall where we will be, over some time up to 2010. This is all approximate, of course. The tank manufacturers reckon that you can capture up to 80% of run off from the roof but real life cases seem to suggest closer to 50%. So, keeping it simple, I will assume that we use everything that we collect from February - September and that we accumulate everything we get from October to January, which have the highest rainfall in the year. Total average annual rainfall is 857mm, of which 384 falls between October and January. Our roof area, including the garage, is 192m2. This gives a volume of 73.7 m3 of water available. Assume that we do, indeed, collect 80% of this, we have just short of 59 m3 to be stored. Hmm - that's a lot of water and tanks with large capacity (~10m3) are outrageously expensive. I think that the limiting factor is going to be budget; over ground storage is cheap as chips but it's finding a way to hide it. Link to comment Share on other sites More sharing options...
Pocster Posted February 10, 2018 Share Posted February 10, 2018 21 minutes ago, vivienz said: In terms of size, I've looked at some Met Office figures for rainfall where we will be, over some time up to 2010. This is all approximate, of course. The tank manufacturers reckon that you can capture up to 80% of run off from the roof but real life cases seem to suggest closer to 50%. So, keeping it simple, I will assume that we use everything that we collect from February - September and that we accumulate everything we get from October to January, which have the highest rainfall in the year. Total average annual rainfall is 857mm, of which 384 falls between October and January. Our roof area, including the garage, is 192m2. This gives a volume of 73.7 m3 of water available. Assume that we do, indeed, collect 80% of this, we have just short of 59 m3 to be stored. Hmm - that's a lot of water and tanks with large capacity (~10m3) are outrageously expensive. I think that the limiting factor is going to be budget; over ground storage is cheap as chips but it's finding a way to hide it. My roof area is smaller and I can collect from all of it . But agree the cost of super large tanks make it uneconomical. I guess it’s either a ‘don’t do’ or accept the compromise of cost against storage .... Link to comment Share on other sites More sharing options...
PeterW Posted February 10, 2018 Share Posted February 10, 2018 I’ve got a spreadsheet somewhere that maps the usage to the rainfall - basically I need 3300 litres and we would be able to use that for toilets and garden etc, an outside tap would be used to top it up if needed but to be honest I can’t see why we would go to that currently as it’s decades on payback. Link to comment Share on other sites More sharing options...
Joss Posted February 10, 2018 Share Posted February 10, 2018 We have rainwater storage of about 10000 litres for the garden (IBC's). This lasts us for around 3 months with no rain during the growing season for a large veg plot. We rarely go longer than this without a top up. As Bitpipe says, you can collect a useful amount in a short space of time. We use gravity and watering cans to deliver the water where it's needed. Link to comment Share on other sites More sharing options...
vivienz Posted February 11, 2018 Share Posted February 11, 2018 I've been looking at @Bitpipe homebrew rainwater harvesting using IBCs that he put into a concrete box. Lovely idea. I'm not having a basement in the new house, though, and wonder how difficult/expensive would it be to dig a nice big hole and then shore it up so that I can replicate @Bitpipe's system. Is there a cost effective way of doing this, given that we'll have a digger on site and will be getting foundations and drains dug. I'm a position of complete ignorance about this, but would really like to see if it's a practical proposition as we'll have a big garden and it seems a shame to waste all that rain water. Link to comment Share on other sites More sharing options...
Bitpipe Posted February 11, 2018 Share Posted February 11, 2018 2 hours ago, vivienz said: I've been looking at @Bitpipe homebrew rainwater harvesting using IBCs that he put into a concrete box. Lovely idea. I'm not having a basement in the new house, though, and wonder how difficult/expensive would it be to dig a nice big hole and then shore it up so that I can replicate @Bitpipe's system. Is there a cost effective way of doing this, given that we'll have a digger on site and will be getting foundations and drains dug. I'm a position of complete ignorance about this, but would really like to see if it's a practical proposition as we'll have a big garden and it seems a shame to waste all that rain water. The RC concrete box was something of accident as we needed egress from basement to meet regs, could have made it smaller (it's decoupled from the basement itself) but thought it would have looked a bit odd. We decided to make a feature of it with a sunken deck and then the penny dropped that we could put RWH under that. I'd guess that by the time you've excavated the hole, got rid of the muck, poured a slab, designed (SE) & built walls capable of withstanding the pressure exerted by the ground etc, you'll have paid for a 4000 underground tank many times over. If you're not connecting to the house then you can forget much of the expensive gubbins. Get one of these and a submersible pump. You'll need to ensure that all your roof drainage meets at a single point to feed your tank through a suitable filter to screen out gunk. Your tank will also need to overflow to a soakaway (where your rain water would have gone anyway). You'll want surface water, from aco drains, to go straight to the soakaway. Allow for power to the tank for the pump. Once hooked up, our 4 1000l IBC tanks filled in a single day of heavy rain... 1 1 Link to comment Share on other sites More sharing options...
vivienz Posted February 11, 2018 Share Posted February 11, 2018 Thanks, @Bitpipe, that's much better value than what I had been looking at. For some reason, I could only find systems that produced potable water. Just the ticket - ta very much. Link to comment Share on other sites More sharing options...
Vijay Posted February 11, 2018 Share Posted February 11, 2018 6000 litre even cheaper https://www.tanks-direct.co.uk/water-tanks/underground-tanks/plastic-underground-water-tanks/6000-litre-underground-water-tank-bt2021.html 1 Link to comment Share on other sites More sharing options...
Bitpipe Posted February 12, 2018 Share Posted February 12, 2018 I get the feeling that when you search on 'rainwater harvesting' you instantly add a premium to whatever you're looking at. Give some thought to your pre-filter system. I've gone for a fine mesh sock inline with the 110mm pipe that all the rainwater runs through before entering the tank., needs quite regular cleaning as it can gunk up fast. I have hedgehogs in the guttering to stop leaves etc getting in in the first place. Link to comment Share on other sites More sharing options...
Cpd Posted February 12, 2018 Share Posted February 12, 2018 2 hours ago, Bitpipe said: I've gone for a fine mesh sock inline with the 110mm pipe that all the rainwater runs through before entering the tank Do you have a link to this as its something i am intrested in, thanks Link to comment Share on other sites More sharing options...
Pocster Posted February 12, 2018 Share Posted February 12, 2018 3 hours ago, Bitpipe said: I get the feeling that when you search on 'rainwater harvesting' you instantly add a premium to whatever you're looking at. Give some thought to your pre-filter system. I've gone for a fine mesh sock inline with the 110mm pipe that all the rainwater runs through before entering the tank., needs quite regular cleaning as it can gunk up fast. I have hedgehogs in the guttering to stop leaves etc getting in in the first place. I agree ! but to get a large tank and all the necessary does ramp the cost up . i do like the ‘ all in 1 ‘ kits though ... Link to comment Share on other sites More sharing options...
PeterW Posted February 12, 2018 Share Posted February 12, 2018 22 minutes ago, pocster said: do like the ‘ all in 1 ‘ kits though ... They are a total rip off... The tanks can be had direct from Balmoral or others for 1/3 price of the specialists. The pumps are Polish, the only clever bit is the electronics but tbh @JSHarris could knock something up with a PIC in an hour to do the same..... you need an airgap for your filler - just use a Hotun tundish - and a valve.... Its not rocket science ! Contrary to popular belief you can bury IBCs, but they need to be encased in concrete. The wire frame acts like reinforcing and you just fill them with water before you cast the concrete and they are good for life. 1 Link to comment Share on other sites More sharing options...
Pocster Posted February 12, 2018 Share Posted February 12, 2018 23 minutes ago, PeterW said: They are a total rip off... The tanks can be had direct from Balmoral or others for 1/3 price of the specialists. The pumps are Polish, the only clever bit is the electronics but tbh @JSHarris could knock something up with a PIC in an hour to do the same..... you need an airgap for your filler - just use a Hotun tundish - and a valve.... Its not rocket science ! Contrary to popular belief you can bury IBCs, but they need to be encased in concrete. The wire frame acts like reinforcing and you just fill them with water before you cast the concrete and they are good for life. Oh ! Bury ibc and pour concrete around !!! If that’s ok ; that’s a massive saving !! Link to comment Share on other sites More sharing options...
PeterW Posted February 12, 2018 Share Posted February 12, 2018 They need 3-4” around them and 6” over the top and if you fill them to the brim then they can easily take the weight. A tank riser for a 300mm IC over the cap will give you plenty of access. 1 Link to comment Share on other sites More sharing options...
Pocster Posted February 12, 2018 Share Posted February 12, 2018 4 hours ago, PeterW said: They need 3-4” around them and 6” over the top and if you fill them to the brim then they can easily take the weight. A tank riser for a 300mm IC over the cap will give you plenty of access. Great ! So what kind of pump ? it needs to only come on with demand yes.? E.g toilet flushes etc . without the electronic control unit I guess some float valve for when the tank gets low mains water is added ? Link to comment Share on other sites More sharing options...
vivienz Posted February 12, 2018 Share Posted February 12, 2018 Very interesting, @PeterW. I rang the Tanks Direct people this morning and they were very helpful. Their tank is no different to any other vessel that gets buried and has varying mass, in that it still needs to go onto a concrete base and have concrete poured around it to anchor it. Other than the capacity, one has to ask what's the advantage over IBCs if these can also be buried, following your method? Very little, it seems, at a much greater cost. Link to comment Share on other sites More sharing options...
PeterW Posted February 12, 2018 Share Posted February 12, 2018 14 minutes ago, pocster said: Great ! So what kind of pump ? it needs to only come on with demand yes.? E.g toilet flushes etc . without the electronic control unit I guess some float valve for when the tank gets low mains water is added ? You can’t use a float valve as you have to have an air gap. Non-submersible are better as you can get a pressure tank version that gives you 3 bar easily for less than £100. No fishing in tanks either when it goes wrong ... just need a simple level indicator and you are done. Link to comment Share on other sites More sharing options...
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