A private water supply is a lifetime investment.
It is therefore essential when considering a borehole quotation that you compare the specification of the construction and not simply the price.
The borehole acts in part as an underground reservoir.
A larger diameter well has a greater surface area allowing more inflow of water.
The larger internal volume means that to extract a given volume of water the drawdown required, is less than that of a smaller well. The recharge is therefore less dramatic, thus increasing the life of the well.
We recommend that the well be drilled no less than 8” diameter which allows for the installation of 5” well screen/liner providing an internal volume which equates to approximately 16 litres of water for every metre. Thus providing a good space or annulus for filter pack and bentonite seal between the borehole walls and the outside casing.
A 6” diameter well would normally have a 4.5” well screen/ liner which equates to approximately 5 litres of water per metre which is considerably less. Furthermore, the annulus between the borehole walls and the outside of the casing is insufficient for the required filter pack and bentonite seal.
It is important that a formation filter pack be installed in the annulus between the borehole wall and the outside of the casing. The purpose of which is to stabilise the well and filter out rock particles from the surrounding strata.
A bentonite seal is applied on top of the filter pack in compacted pellet form which expands when wetted to form a single mass. This prevents any ingress of unwanted water or potential pollutants. The pellet size makes it virtually impossible to install in the smaller annulus, their effect would be unreliable. A larger annulus allows for confident installation which when wetted will form the required single mass seal.
We cannot stress enough the importance of this seals purpose in keeping out surface and near surface water.
Near surface water can contain a cocktail of unwanted substances e.g. sewage effluent, silage effluent, fuel spills, pesticides, bacteria from dead and decaying wildlife and livestock, naturally occurring organic compounds from decaying vegetation or acids from peat deposits.
The size of the water well will determine the size of the pump installed.
We recommend the use of 4” pumps which have an outside diameter of 99mm.
This size of pump is of higher quality, more reliable and generally has a longer life span than the 3” alternative.
When installed within an 8” borehole a 4” pump has sufficient space for operation and allows for easy removal should maintenance be required at a later date.
However, when installed in the smaller 6” borehole it is an extremely tight fit within the well screen. The cable guard on the pump could catch on the well screen joints making it difficult to remove for service or maintenance. Any debris that drops into this situation jams the pump and prevents its removal. In some cases the only answer is to snap off the riser pipe and push the pump to the bottom of the borehole. The length of still connected riser on the final position of the pump may result in a total loss of the borehole.
Borehole pumps find it easier to pump volume rather than pressure. Therefore a large volume well provides a given amount of water at much less drawdown. The pump in a smaller diameter well has to work much harder to deliver the same volume due to the increased drawdown.
Every 10m of drawdown means the pump has to overcome an extra 1 bar of pressure (14.7psi). The extra load on the pump means a higher amp age requirement, therefore a direct increase in electricity consumption.
We believe the construction, quality and reliability of our wells and equipment speak for themselves. Our one stop shop approach means we are able to offer our clients a comprehensive service from construction and installation to service and repair regardless of location.