Q: How much water do I need?
A: Many people moving to New Hampshire have never owned a house with a well and have little understanding of
what works and what doesn't. First, almost all wells in our area are "drilled wells". This means that a deep hole (sometimes
in excess if 500 feet) is drilled into the underlying bedrock. A "casing" or pipe is used until bedrock is reached).
This hole is normally something over six inches in diameter. The two main variables relating to a wells capacity are "recovery
rate", measured in GPM (Gallons per minute) and storage (the amount of water contained in the well hole, above where the
submersible pump is located).
As there are 1440 minutes in a day, it is clear that a well producing one GPM could conceivably produce 1440 gallons per
day, a fair amount of water, except perhaps when irrigation is used. No family uses water at a uniform rate and may in
fact use it at a rate of several gallons per minute, for short periods of time. Without adequate storage even four or five
gallons per minute might be inadequate. The answer to this is storage. When a well is "stable", the water flowing into
it will rise to a level such that the pressure in the water column equals the pressure pushing the water in. This height is
known as the "static level". If the static level was 50 feet below the ground and the pump was at a depth of 450 feet,
the result would be a hole in the ground, six inches in diameter, 400 feet tall, full of water. As there is about 1.5 gallons
in each foot, there would be about 600 gallons of water in storage, a very good buffer. The net result is that large storage
reduces the need for a high flow rate and visa-versa.
When buying a new home, the buyer may have some control over the decision relating to the well, if it has not be installed
prior to agreeing to buy the house. If the well is drilled by us and if no buyer requirements are stipulated, we normally drill
to the point where we have met the FHA spec or a combination of storage and flow rate which will allow the well to produce
at least 5 GMP for four hours. I.e. be able to pump 1200 gallons in four hours.
