Loss of Pressure from the Well

It was hot and the sun was brutal, so we took a break. Grabbing a cold drink we sat in the shade of a tree on the stone enclosure I had built around my well head. I pointed out my new aluminum well cap and the ancient carpenter (who is a couple of years younger than I am) told me about his well problem. He had recently noticed that the pressure from the well had fallen. Was this failure of the well, a piping or an equipment problem?

Failure of the well itself is rarely sudden; generally there is a slow deterioration. However, during a drought it can seemingly happen suddenly. If you have water first thing in the morning and again when you get home from work, but the supply seems to run out especially when doing laundry or taking a shower. Then you may have a groundwater problem. A groundwater problem seemed unlikely after so much rain this past spring, the U.S. Geological Survey (USGS) monitoring wells in our county all show groundwater at or above the mean level for July. So the problem is unlikely to be groundwater.

To provide a reliable supply of water, a drilled well must intersect bedrock fractures containing ground water and recharge at a rate greater than the typical domestic demand of 6-10 gallons per minute or have enough storage in the well itself to supply the pump demand. Each foot of a typical six inch well, has almost a gallon and a half of storage so that a 100 foot of well has 147 gallons. Depending on how deep your well is, the crudest test of the well itself is to see if you can run it dry. My well is only 150 feet deep so running both hoses (which draw about 3 gallons per minute each) would draw down the well in about 40 minutes at normal flow. Even on the deepest home wells it would only take 3-4 hours to know if your can run your well dry, but that would not be necessary. If you have more than about 100 gallons available in well storage it is enough to supply small household needs. At that point it is more likely an equipment or system problem.

from Minn Dept of Health

Equipment problems are the most common well problems. The first step in identifying the cause of a low pressure is to check the equipment. 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, the pipe to the house and the 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 each component in the system and well must remain operational.

If your water supply has lost pressure, and seems to be drizzling out of your faucet or showerhead at all times, your problem could simply be a loss of pressure in the pressure tank or damage to or a leak in the bladder in the pressure tank. So start in the basement. The components within the basement provide consistent water pressure at the fixtures in the house and the electrical switch that turns on the pump. The pump moves water to the basement water pressure tank, inside the tank is an air bladder that becomes compressed as water is pumped into the tank. The pressure in the 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 typically maintains the water pressure between 40-60 psi or 30-50 psi for smaller tanks. After the pressure drops below the cut in pressure (typically 40 psi), the electrical switch turns on the pump and the pressure in the tank increases as the tank fills. If however, the pump is not delivering water fast enough the pressure tank could fail to regain its head while the water is in use. Also, jiggle the tank to make sure that there is not a hole in the bladder and the area above the bladder is not filling with water.

The first two things to check are the pressure in the pressure tank and your circuit breakers to make sure that the problem is not electrical. If there is a short in the pump system it will blow a circuit. So turn off and on the pump’s circuit breakers or change the fuses. Pumps generally have two circuits tied together because an immersion pump draws a lot of power (240 volts). Make sure both circuits are on- a small water drizzle is one sign of a 240 volt pump getting only 120 volts. Next check the pressure gauge on your pressure tank, read it. If it is not showing a pressure of 40 psi (slightly left of center) that could be your problem. Also, turn on a tap and let the water run and while that is happening check the pressure on the tank, to make sure it does not fall. The electrical switch at the pressure tank (grey box under the gauge) turns on the pump. It is probably working since you have water, but check it anyway. Check the voltage before and after the switch just to make sure. When the pressure in the pressure tank falls to 35-40 psi the switch at the pressure tank turns on the pump. Also, you can get what is essentially a vapor lock and the tank may simply need to be drained, bleed and recharged. Before you do that check to make sure that the tubing to the valve is not clogged.

Time to look at what is happening outside. There are two types of pumps; a jet pump and a submersible pump. Most modern drilled wells are built with a submersible pumps. In older pump installations and dug wells, above ground jet pumps were often used, which potentially allowed the introduction of contaminants at the surface concrete well cap and have a fitting called a foot valve. A foot valve is also used at the base of deep wells and is basically a check valve combined with an inlet strainer (older immersion pumps sometimes have what looks like a sock protecting the inlet). Both of these serve as a strainer to prevent picking up rocks or debris that could clog or jam the foot valve. They can get clogged and diminish flow.

At this point, you are going to need help to identify the problem. It is more than a one man (or woman) job to pull a pump. Shallower pumps can be pulled by hand, but special equipment is necessary to pull a deeper pump. Call a well driller or a well repair company. The well drilling companies can generally replace, pumps and pressure tanks and other well components. In addition, they can diagnose an improper well design. Private well construction was not regulated in Virginia until the 1992 (though Prince William County had well regulations going back to 1979). I have seen some funky well designs over the years. In Virginia a license is necessary to work on a well as a certified water well provider. Plumbers generally do not have this certification. Do not call a plumber for a well problem.

Another possible problem is a leak or clog in the pitless adaptor. That is the fitting that allows the vertical well to connect to the horizontal pipe to the house below the frost line. Things like a leaky valve at the bottom of the well can result in a pump losing it prime after a power failure. The submersible pump is a long cylindrical unit that fits within the 6 inch diameter well casing. The bottom portion consists of the sealed pump motor connected to a series of impellers separated by a diffuser that drives the water up the pipe to the plumbing system through the pitless adaptor and a pipe that runs from the well beneath the ground to the basement.

The pipe to the house should run below the frost line, but this past winter was extremely harsh in many locations and a pipe or pitless adaptor might have cracked. If like me your pipe runs under a portion of the driveway, this turns out to be a fairly expensive, but simple fix-excavating the pipe and replacing it. Look for indications of a leaking pipe, sinking ground, cracks in the driveway vegetation that looks a little too lush. If you end up replacing the pipe, make sure you slope it properly. If the horizontal well piping between well and building does not slope continually upwards or if it has a high spot, an air lock can form in the piping, so make sure if you end up replacing the pipe that it is properly slanted and not just a fixed depth below surface. The casing to well itself can also develop leaks over time that can diminish flow.

Finally your pump might be failing. According to the Water Systems Council a submersible pump should last 15 years or more, but silt, sand, iron bacteria and excessive mineral content can impact their life. A submersible pump operating high sediment water may fail in only a few years and a failing pump may appear as diminished pressure before complete failure.

If you need help with a well problem, the Wellcare® Hotline is staffed by the Water Systems Council (WSC), the only non-profit organization solely focused on private wells and small well-based drinking water systems. The Hotline operates Monday through Friday from 8:00 a.m. to 5:30 p.m. Eastern Time, and can be reached at 888-395-1033. Also, if you are in Virginia you can call or email the Virginia Master Well Owner’s Network for help. My name and email are near the bottom of the list with the volunteers and I am happy to help if I can. You have to go through the two step to get my email to avoid spam. http://www.wellwater.bse.vt.edu/contact_mwo_table.php