Borehole FAQ’s

Firstly let us just explain what a borehole is! It is basically a deep hole drilled into the earth down into an underground stream or reservoir. A common misconception amongst homeowners is that boreholes are exclusively for industrial use or there are lots of hidden charges for extracting the water. The only expense is the upfront cost of the borehole, pump and plumbing to the relevant area, plus regular borehole maintenance. Once drilled you are free to extract as much water as you need and at any time!


Boreholes allow us to have access to water which is ideal for many uses. A key benefit is that the water itself is entirely free! The water can be used for many different applications in gardens and horticultural arenas, plus of course commercial applications such as farms, golf courses and hotels, to name but a few.


Whether you’re a home-owner, farmer or industrial business having your own borehole drilled is a big job. It’s one that requires a lot of research, plenty of consideration and you have to be absolutely sure of what you’re getting and how it will benefit you. With that in mind here are some of the most frequently asked questions about our borehole drilling services we get asked by customers on a daily basis.

There are several factors which can affect the cost of a borehole installation this includes: underlying hydrogeology, amount of water required, location, the type of pump required and the depth of the borehole. We are able to provide, free no obligation quotations, simply call us on 07911 713358.

How long a borehole takes to drill depends on the depth of the borehole and the type of matter under the surface the Engineer expects to find. As an example a 150mm diametre borehole drilled to a depth of 30 metres will take around 2 to 4 days and about the same again to install the pumping infrastructure and ensure the borehole walls are secure, construct a small pit to house the relevant non return valves etc.
D.W. Lloyd Limited has specialist knowledge of geology in Guernsey so we are able to give you a firm idea of the materials under the surface we are likely to encounter.

Obviously we cannot simply guess where the underground streams are! Therefore the initial stage is for a water diviner to be called to confirm where there is water (very occasionally water cannot be found) The diviner will present us with several places where he has found water. DWLL can assist in this initial stage.


If there are more than one possible locations, then there are practical decisions to be made. For example where do you want the water to be used, where can the above ground pumping infrastructure be housed, where is the nearest electrical power and are there any potential sources of contamination of the borehole?
As part of our no obligation specification and quotation we will visit the site with our diviner to assist you in determining if there is sufficient space for the borehole and the best location to construct it.

During pumping, a borehole pump produces a ‘cone of depression’. This is the influence zone of where water is being abstracted. Where possible any new borehole should be outside this zone to ensure that one borehole does not affect another.
We recommend that anyone who wishes to site a borehole close to another speaks to us to gain the specialist knowledge they need to make sure the new borehole does not affect the old borehole.

Where possible boreholes should always be a minimum of 50m away from any potential source of contamination such as septic tanks. This is in accordance with Environment Agency guidelines.

On some sites this just isn’t possible but as long as the septic tank or other source of contamination is modern and well maintained and the borehole has been constructed properly with sufficient casing then it should still be viable.

This depends on the scale of the submersible pump installed but typically a small pump for normal use will not be very expensive to run.

Usually borehole water is perfectly safe to drink. However we always recommend carrying out a water testing procedure to fully understand the contents of the water.
There is also legislation in place of course and in cases where the water is inconsistent with the proposed use, for example drinking, or commercial uses we are able to provide water analysis and water treatment services.

There is no set answer for how deep a borehole needs to be. Put simply the borehole should be as deep as is required to reach the aquifer (water bearing rock).
The average depth of a borehole is between 30m and 50m but this can be less as well as significantly more. The depth of a borehole very much depends on where you are in Guernsey and the underlying geology.

We get many enquiries from customers asking “how do I make borehole water safe to drink?”, “What is the easiest way to purify borehole water?” or “How do I remove iron from the borehole / water well in my garden?” This can’t be done with guess work.


The first step is to have your water tested. We work closely with the local States laboratory that can check your water for substances such as iron, manganese, calcium and other minerals and contaminants like bacteria etc.


If your water has failed quality tests for your intended use then you may need to install a water treatment / filtration system.

Filtering borehole water should only be carried out by a company experienced in implementing suitable filtration and UV water treatment systems to purify the water. This is an area that we have many years experience in. Once the right method of borehole filtration has been identified it should be fitted to the required client specification or human potable water standards.

In some cases water may be extracted from the ground under its own pressure. This is known as an artesian well. However in many cases a submersible pump is required to bring water to the surface. Which pump is required depends on various factors, such as the quantities of water required, the desired pressure and its intended use. To get the most from your borehole a pumping system should be designed to suit the client’s exact requirements.

A well-constructed borehole can last many generations. We regularly encounter boreholes from the 1950’s, 60′s and 70′s that are still in full working order and were drilled by people known to us.


Modern technology has also meant that newly constructed boreholes can last even longer due to advancements in borehole lining material and drilling techniques to prevent the borehole from collapsing.

In many cases yes, the old borehole will need to be assessed and if it is still producing water then it can be brought back into commission. It may require maintenance works and a cleaning process to re-develop the borehole yield.

The width of a borehole depends on the volumes of water required. For example if you are wanting to draw large volumes of water for heavy commercial use then a wider borehole would be drilled to allow for a larger borehole pump.

By tapping into borehole water you essentially remove your dependency on mains water. Borehole water is much cheaper than mains water (with bills continually rising) and although there is the up-front cost of drilling the borehole and mobilising a borehole drilling team in many cases the cost can be paid back within a year or so.

Most properties can benefit from groundwater but as this is Mother Nature there is no guarantee.
However carrying out a site visit with our diviner will provide a very reliable indication of location and whether or not water will be encountered.

Boreholes are usually extremely reliable. In fact many of our commercial and agricultural clients use boreholes due to their reliability, whether to feed their livestock or water their fruit and vegetable crops.

One of the mains issue farmers and industries have is variable water pressure from mains water supplies. A borehole solves this problem. Likewise they are sustainable during drought periods meaning that even when mains water supplies are being restricted borehole water supplies can be sustained.