Low Pressure from the Well

A reduction in pressure from the well can have several causes:

1. the well going dry,
2. a leak or blockage in a pipe in or from the well
3. a pump problem
4. a pressure tank or pressure switch problem
5. an electrical problem (pump is running on 120 instead of 240)

Failure of the well itself is rarely sudden; generally there is a slow deterioration. However, during a drought it can seem to happen suddenly when the storage in the well itself is used up in the normal course of the day. If you have water at normal pressure first thing in the morning or when you get home from work, but the pressure seems to fall or the water run out after a little while, then you may have a groundwater supply problem.

While many wells will last decades, over time the amount of water a well yields can decrease. That can be caused by the water table falling due to extended drought, increased use or increased ground cover with roads, driveways, patios and houses in the recharge area. Mineral encrustation and reducing bacteria (often called iron bacteria) buildup can also decrease well recharge by plugging of holes in the well screen, plugging the piping or the filling of openings in the geologic formation itself. According to Penn State Extension the fall in well yield over time can be caused by changes in the water well itself including:

1. Encrustation by mineral deposits
2. Bio-fouling by the growth of microorganisms
3. Physical plugging of groundwater aquifer by sediment
4. Well screen or casing corrosion
5. Pump damage

To provide a reliable supply of water at an adequate pressure for extended use, a drilled well must recharge at a rate greater than the typical domestic demand of 3-5 gallons per minute or have enough storage in the well itself to supply the 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. The crudest test of the well itself is to see if you can run it dry. My well is only 150 feet deep, but the static water level has fallen over the years to 43 feet below grade so running the hose (which draw about 3 gallons per minute) should draw down the well in about an hour. I ran the hose for 16 hours back in the spring an never ran it dry. It recharges faster than I was drawing water.

Even on the deepest home wells it would only take 5-6 hours to know if your well is not recharging fast enough and you can run your well dry. If you have more than about 150 gallons available in well storage it is generally enough to supply small household needs till the well can recharge. At that point it is more likely an equipment or system problem. You can potentially repair an encrustation problem (see https://greenrisks.blogspot.com/2020/03/keeping-your-home-supplied-with-water.html)

Equipment problems are the most common well problems. The first step is to check the equipment. The components of a modern drilled well system likely to impact pressure are: a submersible pump, the piping which can develop a leak or become clogged, a pitless adaptor,  the pipe to the house and the interior water delivery system including the pressure tank and pressure switch.

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. (There are other types of pressure tanks that do not have a bladder and a constant pressure pump does not need a pressure tank, but those installations are not as common.)

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 30-40 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. The pressure switch could also be the problem; it could be cutting in at the wrong pressure.

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. You can check the pressure on most pressure tanks with a tire gauge and the valve on the top. (Be sure to cut the power to the system and open a faucet to drain the tank before you measure the pressure. While the water is running out of the tank check the pressure on the pressure gauge, to make sure it is dropping and the pressure gauge is working). After thatyou’re your tier gauge to checking to see that the pressure in the tank is a couple of psi below the cut-in pressure set on your pressure switch. (Most are set to 38 psi for the 40-60 psi tanks.) When you unscrew the cover over the valve if water leaks out, your pressure tank bladder has failed, and it’s time to buy a new one.

The electrical switch in front of the 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 40 psi (30 for small tanks) 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.

When you turn the pump back on make sure that both circuit breakers are flipped to the on position. If there is a short in the pump system it can blow a single circuit. The pump can operate this way, but not very well. 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. (If you know how to do it check the amperage across the pump to make sure it is steady and within range see the chart below from Franklin Electric.) In most cases the pump operates near the maximum load.

Time to look for problems outside. The pipe to the house or the 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 signs that a pipe outside of the well is leaking, 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 piping in the well itself can also develop leaks over time that can diminish flow.

If you do not see a leak from a pipe outside the well, you are going to have to look at the pump and equipment in the well. 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 if you are a big, strong and young guy, but special equipment is necessary to pull a deeper pump even for a big guy in great shape. 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 very odd 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.

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 can loose it prime. Both types of pump 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.

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 (which is black tubing in the picture) to the plumbing system through the pitless adaptor and a pipe that runs from the well beneath the ground to the basement.The piping or tubing within the well can fail or get clogged.

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.