Topic: Borehole anybody?

[woppa30]

Well, after a few nice warm (dry) days some people are taking the mick with sprinklers left on for hours on end. This has caused the town council to threaten rent increases (on top of the 420% two years ago) to cover the water rates.
Been thinking, has anybody any experience of boreholes on allotments. I am thinking of pricing up a solar / wind powered system that feeds some sort of header talk (several thousand litres...) that feeds dip tanks around the site. Fixes several problems in one go...
No water rates bill (should mean cheaper rent)
no hosepipes (not enough pressure...)
More environmentally friendly (drinking water for my spuds is a bit OTT)

Has anybody any info on price, feasibility etc. I have googled and there are systems available, just looking for somebody with some practical experience....
Thanks in advance,
David.

[gavinjconway]

Probably easier and cheaper in the long run to pay council for water..

[Tee Gee]

I am not sure that it would be legal!

I seem to think that " water" being a "utility" would prevent  you doing it!

As I said I am not sure but I think all  "water" belongs to the local Water Authority,

But I may be wrong!

[Unwashed]

I had a look at the idea once.  I reckoned that it would be difficult to break-even, though it does rather depends on a few things.

For starters you need to be sitting on water-bearing ground.  There are geological maps that can tell you and if you contact a well-drilling company they may also have experience of the area and be able to tell you.  Ideally you'll be sitting on sands and gravels, if you're on rock, chalk or clay it's less easy.

You can dig a well yourself.  Digging a big deep hole and lining it with brick as you go down is technically difficult and dangerous, but the well only actually needs to be around 3" diameter, not 3', and an inventive way of doing it is by repeatedly plunging a length of rigid pipe while you push water down it and let the water carry the spoil away.  It works well by struggles on stony ground.  A professional well-drilling company will charge several thousand I believe, so it would pay to get some prices to get a ball-park cost.  Friends recently had a domestic well sunk and I think that was in the region of £20k for all the works and that went down some 30m I think.

If you're on mains electric it's a whole bunch easier because the solar options adds to the cost and complexity.  With solar you probably don't need batteries, you just let the sump pump run when the sun shines and store the water in a series of tanks above ground.  You'll need float switches to stop the pump running either when the well's dry or when the header's full.  If you're on mains then a high-pressure pump in the header to feed the dip tanks at 3 bar is possible, but on solar you'd need more panels and would almost certainly need a bank of batteries so the dip tanks would re-fill on a dull day.

You need to think about peak demand.  Dip tanks don't have much capacity - half a dozen watering cans and that's it, so think about the required peak flow at busy times - how many allotmenteers do you want to support watering heavily simultaneously - under-spec the system and your allotmenteers will complain about the lack of water, over-spec the design and they'll complain about the cost.

Water is somewhat reluctant to flow down pipes and needs a certain head of pressure to drive a given flow through a pipe of a given bore.  From the specification above you'll know your max flow rate, and knowing the dimensions of your site and the locations of the dip tanks you can work out the total length of pipe (and you need to add a bit for bends and valves) and that will allow you to estimate the required head.  Sitting several thousand litres on a stack of pallets 3' in the air is not necessarily any great problem, but once you start needing more than a metre or so then you really need to think seriously about the structural engineering of the stand, because you don't want several tonnes of water tank just falling over, and you need to think about worst case, like 70mph winds and such. 

A low head system is safer, but you may need quite a large bore pipework main to deliver that.  1/2" MDPE pipe is really cheap, but it gets very much more expensive as the bore diameter goes up.  You can estimate the head loss for a given flow through a given length of pipe of a given diameter using the Darcy-Weisbach equation, but it may take you a little research to work out how to use it - but it's pretty straight forward.

If I remember right I found that recycled 1000 litre IBC tanks gave the best price per volume storage.  Guestimate how big your above ground reservoir needs to be - I'd guess you'd want to store several days of the peak demand, but that's just my guess.  Just couple the IBCs together with large bore pipe and they'll act as a single reservoir.  You might possibly find that distributing the IBCs around the site next to dip tanks and filling them from a small-bore main direct from the sump pump would allow you to use very shore length on large bore pipe from the IBCs to the dip tanks - the sump pump will be a high-head-low-flow pump so you can get away with a smaller bore pipe to the headers than you can between the headers and the dip tanks where you have high-flow-low-head.

Any road, those were my thought, but I never put any of that into practice so I don't know how useful it might be to you, but I hope that it might give you some ideas to develop.

Water from the water company costs in the region of £1/cubic metre, and there's a standing charge too depending on the bore of the site main - the water companies publish their charges on their web sites.  Make sure you're not being charged for foul water disposal - they assume that a reasonable proportion of the water they sell ends up coming back down the sewers and that charge for that too, so if you can show that none returns down the sewer you can claim a discount.  That should allow you to make an informed judgement on whether you think you can provide water more cheaply with a well, spreading the cost of the system over the lifetime - 10 years is probably reasonable, but that's quite a long time to be looking for payback because various things can fail in that time.  My feeling is that a 5-year pay-back might be reasonable, but any longer isn't worth the risk, but that's entirely up to you and your situation.

[Unwashed]

I am not sure that it would be legal!

I seem to think that " water" being a "utility" would prevent  you doing it!

As I said I am not sure but I think all  "water" belongs to the local Water Authority,

But I may be wrong!

It depends on how much water you plan on abstracting.  I can't remember the limit off the top of my head, but it's quite a lot before you need an abstraction license - and I think that comes from the Environment Agency rather than the water company.

[woppa30]

A bit of googling late lat night, you can extraxt 20 000 litres a day without permission from your land. Thats 20 cubic meters.
Food for thought. Also found this...

http://www.geologicboreholes.co.uk/case-study/solar-powered-water-pump-installed-on-remote-borehole/

The BGS site has some farms nearby as having a well, my daughter knows one of them through work so I will be finding out how far down the water table is...
David

[Robert_Brenchley]

How would you go about digging a simple well? I'm thinking about six feet down; I have water since I'm by a stream, but it dries up some summers.

[squeezyjohn]

It really depends on what is under your land!  If you're sitting on rock then it's not an easy matter at all.

I've dug a simple experimental well on my allotment using nothing more than a spade, a bulb planter screwed to a long stick and drain rods with the screw attachment.  I hit water about 8-10 foot down and ended up just over that in depth.  Fortunately it seems to be just clay, clay and more clay where I am and although it's really sticky and not the easiest job in the world - it's perfectly do-able in a few hours.  My hole was only about a foot across though and wells like that take a while to re-fill with the water.

If you've got mains water on your site - it would be well worth having a go at this method which frankly seems much easier as the water pressure just pushes the debris up.  All it needs is PVC pipe, a few fittings and a pressurised water supply.

http://www.youtube.com/watch?v=XGq0ETzZP0E - drilling a borehole well

and a great (but long!) instruction of making your own hand pump from just plumbing parts at https://www.youtube.com/watch?v=j_RqQ3elzNU&list=PL6F5B48EE13E0F8E4

I made my own pump this way and it really works!

[Robert_Brenchley]

It's silt from the stream. I don't know how deep that goes, but I doubt whether there's anything like solid rock under it. I believe there have been wells on the site in the past.