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Kitchenwitch
Joined: 18 Apr 2006
Posts: 25
Location: Devon
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 Posted: Sun Jan 28, 07 10:10 am Post subject: Grey water, low-pressure garden-related conundrum... |
 
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Hi all,
We have a gardening-related water issue that I'd be glad to hear opinions about...
We have a private water supply, a small and relatively shallow well which is underneath our kitchen. The well has an electric pump which fills up a water tank also in the kitchen, meaning that we have only about a seven-foot drop for water pressure, which you can imagine rules out power showers for the time being!  BUT my ultimate ambition isn't to run a power shower, but to find a way of watering the garden which doesn't take two hours a night (that's what we spent last summer doing...), and which manages to re-use bath water etc.
Last year, we re-plumbed our bath and basin (our bathroom is downstairs, very near the well, all housed in the same miserably damp extension) to drain into a small tank outside, and we then used the water for vegetables etc (using only eco-friendly stuff in the water, I hasten to add); trouble with this is that the soap rapidly degrades, meaning you end up with nasty, nasty water which you wouldn't really want to put anywhere near something you're hoping to eat...!
Tied in with the pressure problem is that we nearly ran out of water full stop last summer - our well is only about twelve feet deep, and is apparently more of a catch-pool than a proper, 'I tap into underground springs'-type affair. So, we can't just use it and think what the hell - we may well need to re-use bath water because, if it's anything like last year, that'll be all we dare use...
What we'd like to do is have some way of pressurising water so that we could run a hose from the bath water, or something similar. Any ideas, anyone? We have energy and enthusiasm, but not much cash! |
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wellington womble
Joined: 08 Nov 2004
Posts: 15051
Location: East Midlands
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| Posted: Sun Jan 28, 07 10:46 am Post subject: |
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HDRA do soaker hose systems that are designed to run off a water butt, so I'd imagine they'd run off your tank. I think a couple of people run them here. A soaker hose system is great, as you can just leave it on for a couple of hours, and get on with other things. They are often made from recycled tyres too. I used to leave mine on overnight once a week, rather than a hour a night, but I don't know if actually makes any difference. Nothing died from lack of water, anyway.
Can you re-use your grey water in the house too - for flushing loos or running the washing machine? If you were only using 'your' water for drinking, and reusing the bathwater for everything else, perhaps you could drain the greywater every couple of days (possibly via the soaker hose, onto the garden!?)
How long does the greywater keep? Do you use enough to keep you in garden water, or is there too much, and some is going to waste. I'd guess it depends on how much of what you use, and how long you can store it for. Don't forget that you can store rainwater in a covered butt (or a seperate tank) and that will keep much better, so you could have a reserve in case you run out. On the other hand, you may have more than ebough greywater to keep the garden and the loos going, and be draining it at regular intervals to stop it going narsty. in which case, perhaps you could rig up the plumbing so you are bathing in rainwater, and just keep the well for kitchen use?
I think perhaps all we downsizers should be feeding up a pet plumber with home made wine! |
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dougal
Joined: 15 Jan 2005
Posts: 7184
Location: South Kent
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| Posted: Sun Jan 28, 07 2:55 pm Post subject: |
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An awful lot has to do with height.
The drain from a downstairs bath is going to be pretty low.
Your existing tank has to be below that.
And to water the garden from that tank, the garden must be lower still. 
Other than living on a hillside, the answer to the 'conundrum' is that the water must be moved higher, somehow.
You are going to need a higher tank, somewhere, and a pump to move the water into that tank. Having the second tank allows you to store the water at high(er) energy. Your pump doesn't have to be related to the flow (or time) when watering, filling a loo cistern or whatever.
You'd probably still need low pressure soakers etc. Normal water mains pressure is equivalent to a tank height of about 60 feet.
If you have a bit of strong flat roof, that might do to support the high tank, or possibly inside the roofspace/attic.
I said *strong* because water is heavy. 1 litre weighs 1 kilo. 500 litres is therefore half a tonne. (A bathful is about 50 litres, ymmv.)
If you fancy trying to use grey water for loo flushing, that too may influence the high tank's location. A loo flush should use rather less than 10 litres. Standards have varied with time, and IIRC place.
The height that you are trying to get to will determine what you need in the way of a pump. Where it might be mounted is another determinant. Some pumps don't 'suck' up the water and so need to be installed lower than the bottom tank.
It'd be nice to power the pump from solar, but that's probably a bit high on capital cost - a solar fountain pump isn't going to lift the water more than a metre or so. And the lifting height is probably the most important part of the pump specification.
Solar power would be neat because the greatest need for irrigation is going to be at those times when solar energy is most abundant. You could slowly pump the water to the high tank all day, ready for the evening watering session. But cheap solar pumps are pretty anaemic.
A worthwhile thing would be to fit the high tank with a float switch, to turn the pump off when the high tank is full.
If you could arrange the high tank just below gutter level, then you could feed it with rain from those gutters - without pumping!
As regards greywater storage. Keeping the tank dark (ie lidded) and cool (so out of the sun) should reduce the fermentation.
I'd expect that it would be worthwhile having three outlets from your greywater collecting tank.
- an overflow, which you could allow to flush away any floating scum (could you use rainwater to promote that overflow cleaning?)
- a bottom tap, for removing any settled sludge (which would likely go on the compost heap very happily...)
- and your normal outlet, something like 3/4 of the way down the tank - where you can draw off the most water that is as clean as possible.
I think it'd be worthwhile to take trouble to ensure that incoming water 'stirs up' the sludge as little as possible. Perhaps a manifold in the tank with its outlets pointing upwards? |
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Barnie
Joined: 26 Jan 2007
Posts: 40
Location: SW/Wales
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chez
Joined: 13 Aug 2006
Posts: 35935
Location: The Hive of the Uberbee, Quantock Hills, Somerset
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dougal
Joined: 15 Jan 2005
Posts: 7184
Location: South Kent
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chez
Joined: 13 Aug 2006
Posts: 35935
Location: The Hive of the Uberbee, Quantock Hills, Somerset
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Barnie
Joined: 26 Jan 2007
Posts: 40
Location: SW/Wales
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Kitchenwitch
Joined: 18 Apr 2006
Posts: 25
Location: Devon
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| Posted: Sun Jan 28, 07 7:22 pm Post subject: |
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Thanks for the suggestions, all.
Dougal, you've hit the nail right on the head. We need to live on a hill! Our house sits in the middle of our garden, which gradually slopes downhill. So, we get some drop from the (downstairs) bath to the storage tank we use for the grey water, but not much (I'd say less than two feet - we've got the world's slowest-draining bath - it could win prizes). We put the water through a basic filter (wire mesh) before it reaches the first tank, and then anything beyond that first tank's capacity is diverted to two water butts by our greenhouse (further downhill still, probably about six to eight feet lower than the bath).
The flat roof option isn't a runner, unfortunately, as our house is thatched with a tin-roof extension which has seen far, far better days. But we might manage something around the back of our house, where we have a traditional Devon bank which is both substantial and flat-toppped, as well as being about eight feet tall!  I really like the idea of a solar pump too - must find out more about that - and the soaker hoses for the remnants. I think that draining the system as we fill it is at least part of the answer - we have quite a few vegetables growing, so we do need quite a bit of water, and just finding a way to take this down from being a two-hour operation would be such a boon... |
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