The Basics of a Well

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 least through the overburden and possibly to the bedrock or in some instances the water table depth. 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 pressure tank in the basement solves this problem by serving as storage and pressure boost, so when you turn on a faucet, the water flows. 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.

A well can last 50 years (I know of one well that did). However, a drop or complete loss of water production from a well can sometimes occur even in relatively young wells due to a lowered water level from persistent drought, nearby development, or over-pumping of the well which can dewater the water-bearing zones. More often, the fall in well yield over time can be caused by changes in the water well itself. According to Penn State Extension these changes can include:

• Encrustation by mineral deposits 
• Bio-fouling by the growth of microorganisms 
• Physical plugging of groundwater aquifer by sediment 
• Well screen or casing corrosion 
• Pump damage 

Monitoring of a well’s performance brings everything into view, good or bad, and allows for preventive maintenance. While many wells will last decades, not all will last that long.  My well is 21 years old.  When I had the pump and pressure tank replaced a few years back, I got a reading on the static water level. It was about 16 feet lower than recorded on the well completion report. That is a bad sign for the groundwater. Nonetheless, the problems I am most likely to experience are mechanical.

How long a well lasts depends on many factors; the geology and hydrology of the region, the amount of ground cover nearby, how the well was constructed, what equipment has been installed “down hole,” and what maintenance activities have been performed to date. Over time every component of a water system will fail. My water “burped and sputtered” one morning and I decided that was my warning and replaced the pump and pressure tank and pressure switch the next spring. The well had passed what I had determined was the median life of a pump- 15 years and I preferred to schedule my pump replacement.)

As a water well ages, the rate at which water may be pumped referred to above as the well yield tends to decrease. The mechanical components and the well structure, screens and casing all age and deteriorate. Well maintenance and monitoring of the water and well’s performance is important in keeping the water flowing. A well owner must think about their well in terms of stewardship over the long term, long before your well fails.

Well casings are subject to corrosion, pitting and perforation. Iron bacteria and scale will build up in fittings and clog the 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.

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.