While many wells will last decades, it is reported that 20 years is the average age of well failure that is well failure, not pump failure. Well casings are subject to corrosion, pitting and perforation. According to Marcus Haynes of the PW Health District the effective yield from a well can fall 40-50% or more over 20-30 years, so a low yielding well might have an effective life of only 25 years. The mechanical components of a well; however, are usually the first to fail and some components fail much sooner. Some kind of equipment failure usually occurs in the first 10-20 years.
The essential components of a modern drilled well system are: a submersible pump, a check valve (and additional valve every 100 feet), a pitless adaptor, a well cap, 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.
To ensure water reaches the tap, the well system within the house must also function. The components within 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. Each component can break or fail.
Submersible pumps used in modern drilled wells are more efficient than older style jet pumps and should last longer, but silt, sand, algae and excessive mineral content can impact their life. There really is not good data on equipment life in private well market, most of the data is from light industrial and community systems and the life of the single family home pump is extrapolated from that and equipment tests. A submersible pump operating in low-sediment water may have a 15 year life while the same pump in high sediment water and without adequate sediment and check valve protection may fail in 5 or 6 years. About 10% of the pumps in my neighborhood have failed in the first 8 years and another 10% have had component failure requiring a repair in that time.
High sediment and mineral content of the groundwater acts as an abrasive and can wear out the pump bearings and other moving parts, causing the pump to fail prematurely. The check valves protects the water pump from loss of prime and having to work as hard each time the pump is activated. A failure of a check valve can result in premature failure of the pump. So, if a problem with the check valve is identified the pump could be repaired before it fails prematurely. A loss of water or a failed pressure switch both result in no water when you turn on a tap. Any change in your water should be looked into, not ignored.
If you have a well, maintaining water to your home is your job. Understanding your well, and water system is important. First of all you should know your system. You should have a copy of you well completion report to know the basics of your well. Also, after five years and every couple of years after that you should have a well maintenance inspection. According to a poll conducted by the National Groundwater Association 80% of respondents had never had a well maintenance inspection and truthfully if you called a service provider they probably would not know what you were asking for. It seems that the expected behavior is to wait until your pump or well do not work and then spend possibly days without water while you call around to find someone to get your water back on. The first time you think about your well (after the initial bacteria test when you bought your house) should not be when the well stops working.
In the past couple of years the Virginia Rural Household Water Quality Program has been working with well drillers and licensed well professionals do develop an affordable and effective well inspection service. It is still in the works, but the basics of such an inspection are:
- A flow test to determine system output, along with a check of the water level before and during pumping. This can cost several hundred dollars, but is important before purchasing a home especially when a well is over 20 years old.
- A pump motor performance (check amp load, grounding, and line voltage).
- Check pressure tank psi, pressure switch contact, and check for leaks.
- Inspect the well equipment to assure that it is sanitary and meets local code requirements, the well cap is still secure and the exposed well pipe is still sound.
- Test of your water for iron, manganese, nitrate, lead, arsenic, fluoride, sulfate, pH, total dissolved solids, hardness, sodium, copper, total coliform bacteria and E. Coli bacteria, appearance, taste and anything else of local concern.