If you use a lot of water for your plot and don’t want to rely on the expensive mains supply, you might consider drilling a well or borehole. Wells are inexpensive provided the water table on your property is high and the water quality is good. Boreholes use exactly the same principle, but they are much narrower with an impermeable liner. This means you can drill down to a deeper aquifer, which cannot run dry and is less likely to become contaminated by surface water, sewage and so on.
The UK has been slow to introduce compulsory water meters, but the government is keen to see 80% of all households metered by 2020. This could prove expensive for homesteaders, particularly if they irrigate from the mains. Note that ground water is a renewable resource, but not an infinite one: you should still catch, store and use as much rainwater as you can.
The stages of drilling a borehole
- Get a groundwater extraction survey from British Geological Survey or other specialist surveyor. This isn’t compulsory, but it will tell you how far down the water is likely to be and what sort of rock will have to be drilled through. You can also use BGS’s borehole browser to see if any neighbours have already had surveys done. If they will share the data you may save yourself the cost of the survey.
- Pass this information to a few borehole companies, and ask them for an estimate. There is still an element of luck when you drill, so ask what will happen if they hit water more early than forecast – or if they do not find water at all.
- Contact the Environment Agency (in the UK) to register for a license if necessary – this is not expensive but it does take time. At the time of writing no permission is necessary if the borehole will be used to abstract less than twenty cubic meters of water a day. Twenty cubic meters is equivalent to 20,000 litres (just under 4,400 gallons). If you intend to abstract more than this, ring the Agency before you get the survey done. They will check that there are no local reasons such as contamination or over-abstraction that would cause them to refuse you a license.
- The contractor drills, then installs pipework, cables and a submersible pump. The borehole is flushed through to clear the supply, and a sample of water is sent for testing. The total time from drilling to test result is usually around four weeks.
How much does a borehole cost?
At the time of writing (May 2011) costs are likely to fall between £5000 and £8000, but the borehole company’s estimate will give you a much better idea. The cost mostly depends on the result of the geological survey, because that will determine the likely depth and rock types of the hole. A pump is usually necessary to lift the water from the aquifer. If the pump ever fails your water supply will stop immediately, so a storage tank is a vital precaution just as it is for other forms of supply. If you are extremely lucky and drill into an aquifer which is under pressure, then you won’t need a pump and a storage tank is probably unnecessary. Other expenses may include an electric pump to lift the water out of the ground, a storage tank if you require one, and appropriate filters and/or UV steriliser if the water quality is not ideal.
Running costs are low provided you don’t insist on remaining connected to the mains water system, which can create additional expense. Modern borehole wellheads can be hidden away in an underground enclosure, and even if filters and/or a UV unit are needed, these are no bigger than a large fridge and can be sited in an outbuilding.
Lifetime of a borehole
A new borehole, installed to a high standard using modern materials such as PVC and stainless steel should last a lifetime. Borehole installation is an area where contractors can cut their costs in ways that cannot be seen until much later, so the least expensive quote is not necessarily the best. Choose a contractor with a proven track record and a written guarantee. If they offer a maintenance contract it is likely that their work will be of a high standard.
Combining with a Ground Source Heat Pump
Ground Source Heat Pump installations also need a geological survey and can be vertically installed using a borehole. If you are considering a vertically-installed GSHP you can investigate the very efficient open-loop type installations, which can be used for drinking water abstraction as well as offering free heat.
- US: The EPA maintains a state-by-state list of well links.
- Australia: Varies by region. You should get advice on necessary permits from a local drilling company.