Well Pressure Tank Problems: Signs, Causes and Fixes
A well pressure tank is easy to overlook until the water pressure starts acting differently. You may notice the pump turning on every few seconds, a sudden pressure drop in the shower or a clicking sound near the tank. These symptoms often point toward the pressure tank, but low well water pressure can have several possible causes.
The pressure tank, pressure switch, well pump and connecting piping all work together. Proper diagnosis means testing the complete system instead of replacing a tank based on one symptom.
What Does a Well Pressure Tank Do?
A pressure tank stores a small amount of usable water under pressure. Inside most modern tanks, a rubber diaphragm or bladder separates the water from a sealed cushion of air.
When a faucet opens, the compressed air pushes water out of the tank. The pressure gradually falls until it reaches the pressure switch's cut-in setting. The switch then starts the well pump. The pump refills the tank and supplies the home until the system reaches the cut-out pressure.
A common residential setting is 40/60 PSI. The pump starts near 40 PSI and stops near 60 PSI. Some systems operate at 30/50 PSI or use a constant-pressure control instead.
The tank does not make the well or pump produce more water. Its main jobs are to provide a reserve of pressurized water, smooth out pressure changes and prevent the pump from starting every time someone uses a small amount of water.
Common Signs of a Bad Well Pressure Tank
The well pump turns on and off rapidly
Rapid cycling is one of the clearest signs that something is wrong. You may hear the pressure switch click repeatedly while a faucet is running. The pressure gauge may also move quickly between the pump's start and stop pressures.
This often happens when the tank has lost its air cushion or the internal diaphragm has failed. Without enough usable drawdown, a small amount of water causes the pressure to fall and the pump to start. The pump then reaches the shutoff pressure almost immediately.
Rapid cycling is hard on the pressure switch, pump controls and well pump motor. It should be corrected before it causes a more expensive failure.
Water pressure rises and falls noticeably
Some pressure change is normal on a traditional 40/60 system. The pressure will gradually move between the switch settings as water is used. It should not feel like the water repeatedly surges, disappears or changes dramatically every few seconds.
Large swings can come from a waterlogged tank, an incorrect air charge, a failing pressure switch, restricted piping, a weak pump or a demand that exceeds the well system's available flow.
The pressure drops sharply before the pump starts
If the pressure falls below the normal cut-in point before the pump responds, the pressure tank may have too much air relative to the switch setting. The tank can run out of usable water before the pressure switch starts the pump, causing a brief drop in flow.
The problem can also be caused by a clogged pressure-switch nipple, a poorly located switch, inaccurate gauge readings or a switch that is worn or out of adjustment. Adjusting the switch may hide the symptom without correcting the cause, so both the tank charge and actual switch operation should be tested.
Water comes out of the tank's air valve
Most precharged tanks have an air valve that looks like the valve on a tire. If water comes out of this valve, the internal diaphragm or bladder has usually failed. Adding air will not provide a lasting repair because the air and water are no longer properly separated.
In most residential tanks, a failed internal diaphragm means the tank needs to be replaced.
The tank or nearby piping is leaking
A leak may come from the steel tank itself, the tank tee, a threaded fitting, the pressure gauge, the relief valve or the pressure switch connection. Rust around the bottom of the tank can indicate a slow leak or repeated condensation.
A leaking steel tank should not be patched or ignored. The tank holds pressurized water, and corrosion can continue beneath the visible surface.
The pump runs whenever a small amount of water is used
If flushing a toilet or briefly opening a faucet immediately starts the pump, the tank may have very little usable drawdown. This can happen when the tank is waterlogged, improperly charged, damaged or too small for the pump.
It is normal for the pump to start after enough water has been used. The concern is how often it starts and how long it runs once it starts.
Why Well Pressure Tanks Lose Their Air Charge
A precharged pressure tank should hold its air charge unless air escapes through the valve or the internal separator fails. Common causes include:
A leaking air-valve core
A damaged bladder or diaphragm
An incorrect initial precharge
Corrosion or physical damage to the tank
Checking or adjusting the tank while water pressure is still present
Older non-bladder tanks operate differently and may gradually absorb their air cushion into the water. Those systems can use an air-volume control and require a different diagnostic process.
What Should the Pressure Tank Air Charge Be?
For a conventional precharged tank, the air pressure is generally set 2 PSI below the pressure switch's cut-in setting. A 40/60 system would normally use a 38 PSI precharge. A 30/50 system would normally use 28 PSI.
The tank must be isolated from the well pump and completely drained of water pressure before the air charge is measured. Checking it while the plumbing is still pressurized gives a misleading reading.
The manufacturer's instructions and the actual pressure-switch settings should always be confirmed. Do not assume the system is operating at the numbers printed on the switch cover. Switches can be adjusted, gauges can be inaccurate and old sensing ports can become restricted.
Is the Tank Always the Cause of Short Cycling?
No. A bad pressure tank is a common cause, but short cycling can also result from:
A failing check valve that lets pressure drain back toward the well
A pressure switch that is damaged or incorrectly adjusted
A clogged switch nipple or tank tee
A pump that is oversized for the available tank drawdown
A water-treatment system or fixture using water unexpectedly
A constant-pressure control or pump controller that is not operating correctly
This is why a complete diagnosis should include the tank precharge, pressure-switch operation, pump run time, system pressure and whether the system loses pressure when no water is being used.
Can a Bad Pressure Tank Damage the Well Pump?
Yes. Electric motors experience their greatest stress when starting. A failed or undersized pressure tank can make the pump start far more often than intended. Over time, this can damage the motor, pressure switch, control box and other electrical components.
Replacing a failed tank promptly is usually much less expensive than waiting until the tank and well pump both need replacement.
How Is the Correct Pressure Tank Size Chosen?
The gallon number printed on a pressure tank is not the amount of water you receive between pump cycles. Only part of the tank's total volume is usable drawdown. The amount changes with the tank model and the pressure-switch settings.
Proper sizing considers:
The well pump's flow rate
The pump manufacturer's minimum recommended run time
The pressure-switch settings
The tank's rated drawdown at those settings
The home's peak water demand
Whether the system uses a standard switch or a constant-pressure control
Installing a larger tank can increase the time between pump starts. It cannot correct a weak well, plugged piping or a pump that cannot meet the home's demand.
How Long Does a Well Pressure Tank Last?
There is no exact replacement interval. Water quality, tank construction, pump cycling, installation quality, moisture and operating pressure all affect tank life.
Rather than replacing a tank based only on age, test its air charge and drawdown and inspect it for leakage or corrosion. A tank should be replaced when it leaks, cannot maintain the correct air charge, has a failed internal diaphragm or no longer provides adequate drawdown.
Can You Add Air to a Well Pressure Tank Yourself?
Adding air may correct a low precharge if the tank and diaphragm are still sound. It will not repair a leaking tank or ruptured diaphragm. Adding air without fully draining the water side can also result in the wrong setting.
Well systems combine electricity, pressurized water and automatic pump operation. Power to the pump must be shut off and water pressure must be safely relieved before the tank or pressure switch is serviced. If you are unsure why the pressure changed, testing the whole system is safer than repeatedly adding air or turning the switch adjustments.
Well Pressure Tank Service in the Western Minneapolis Suburbs
If your well pump is cycling rapidly, your water pressure is dropping or your pressure tank is leaking, Predictable Plumbing can diagnose the plumbing system and explain what is actually causing the problem.
We test the pressure tank, air charge, pressure switch, gauge and system operation before recommending replacement. Predictable Plumbing serves homeowners in Medina, Corcoran, Maple Plain, Independence, Greenfield, Delano, Plymouth and surrounding communities west of Minneapolis.
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