Thursday, December 4, 2014

Water Well Basics

Nationally about 14% of domestic water is supplied from private wells. In Virginia, still a very rural state, about 21% of domestic water is supplied from private wells. If you have a private well you are responsible for making sure that you have water in your home and it is safe and pleasant to drink yet, I’ll bet that no one ever taught you the fundamentals of a well so that when there is a problem, you have a frame work to narrow down the causes and solve it.

Wells are a combination of natural and mechanical systems that serve to move water from fractures or cracks in the bedrock or pore space between grains of sediment or sand in the earth into the well and from there into the house. Generally speaking a modern well should be drilled through the loose “overburden” of top soil, sand and sediment into the bedrock below. In geology that has groundwater, water will flow from any fractures that intersect the open borehole. In wells drilled in areas where the sediment and sand are more than a hundred or two hundred feet deep, water will flow from the pores or spaces into the well. A well should have a casing that extends at east through the overburden and possibly to the water table. In bedrock a well borehole can simply be open, but in sandy soils the borehole will require a well screen liner or slotted casing to prevent the borehole from collapsing or filling with sand and silt. Well casings used to be made of steel, but these days plastic piping is becoming more common.

For the plumbing system to function properly, the recharge rate in the well would either have to equal the pumping rate or there has to be adequate storage in the system- either a storage tank or the well itself. The recharge rate or the well recovery rate is the rate that water actually flows into the well through the rock fissures. If the well cannot recharge at the same rate at which water is being removed and does not have adequate water reserves then the well, the system would suffer intermittent episodes of severe water pressure loss. The information on your wells performance can be obtained from the water well completion report on file with the department of health. The “stabilized yield” is the recharge rate.

While many wells will last decades, it is reported that 20 years is the average age of well failure. Over time every component of a water system will fail. Older well pumps are more likely to leak lubricating oil or fail. Well casings are subject to corrosion, pitting and perforation. Iron bacteria and scale will build up in fittings and clog pitless adaptors and pipes. A water pressure loss can result from a pump that is too small for demand, inadequate or a failing pressure tank, or a buildup of scale in the pipes. There are a number of reasons why a well might stop producing water, but basically they break down into equipment failure, depletion of the aquifer or other groundwater problems and failing well design and construction.
Sanitary well cap

The essential mechanical components of a modern drilled well system are: a submersible pump, a check valve (and additional valve every 100 feet), a pitless adaptor (a fitting that makes a 90 degree turn to make the connection between the water line in the well and the horizontal pipe that runs below the frost line to the house), a well cap (sanitary sealed), electrical wiring including a control box, pressure switch, and interior water delivery system. There are additional fittings and cut-off switches for system protection, but the above are the basics. To keep the home supplied with water the system and well must remain operational.
The components within the house (usually in the basement) provide consistent water pressure at the fixtures. The pump moves water to the basement water pressure tank, inside the tank is an air bladder that becomes compressed as water is pumped in. The pressure tank moves the water through the house pipes so that the pump does not have to run every time you open a faucet. The pressure tank maintains the water pressure between 40-60 psi. After the pressure drops to 40 psi, the switch turns on the pump and the pressure in the tank increases. Over time the bladder becomes stiffer and water pressure is lost. Also, the pressure tank can lose some of it’s charge or become water logged.
my pressure tank- Goulds made my pump and slapped their label on the pressure tank

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