Well Pressure Switch Problems

Start with the gauge

Find the pressure gauge on the pipe near the tank. Run a faucet and watch:

• Does the pump turn on when the pressure falls to the cut-in? Note the number.
• Does it turn off at the cut-out when you close the faucet?
• Does the needle drop slowly and steadily, or does it jump around?

Those three answers sort almost every switch complaint. On a submersible pump you often can't hear the pump at all; Boshart notes the gauge gives you a way to monitor the pump's operation and run times. If the gauge itself is stuck or full of water, replace it first. You can't troubleshoot with a bad gauge.

Likely causes

1. 1

   Cause 1: The switch clicks on and off rapidly

   Rapid clicking is usually the tank, not the switch. Boshart lists rapid on-off switch clicking, short cycling and a jumping gauge needle as signs of a waterlogged pressure tank. Knock on the upper part of the tank. A healthy tank is mostly air and sounds hollow, Boshart says about 70 to 75 percent air. A dull thud all the way up, or a cold, sweaty top, means the bladder has failed or the air is gone.

   Boshart is blunt about why this matters: a waterlogged tank will burn out your pump. Go to well pressure tank problems before you buy a switch.

   If you have a piston pump, rapid chatter can also come from pressure spikes on each stroke. Those pumps need a switch with a pulsation plug, which slows the water into the diaphragm so the switch ignores the spikes.

2. 2

   Cause 2: The pump won't turn on

   Pressure is below cut-in, the breaker is on, and nothing happens. Boshart names two causes:

   • A clogged inlet. The tube or 1/4-inch nipple feeding the switch diaphragm gets blocked with sediment, iron or rust. The switch never sees the low pressure. A switch that starts when you tap the box is the giveaway.
   • A worn mechanism. The linkage wears out after years of use, or debris lodges in it.

   Either way the fix is cheap. Replace the nipple, and if that doesn't do it, replace the switch.

3. 3

   Cause 3: Burned, pitted or stuck contacts

   With the power off, look at the two sets of contacts. Some pitting is normal, and Boshart says not to sand, file or chemically clean them. Heavy burning, melted plastic or contacts that are welded shut mean the switch is done. Welded contacts can keep the pump running nonstop until something breaks.

   Square D sells contact replacement kits for its Pumptrol switches, such as 9998PC241 for FSG and FSW models, which includes a new diaphragm. A whole new switch costs little more.

4. 4

   Cause 4: The settings are off

   If someone has been turning nuts, the switch may be set beyond what the pump can reach, so it runs and never shuts off. Or the differential has been cranked so wide the pressure swings hard. Boshart says most messed-up switches come from adjusting the differential nut. Its fix is to measure the nut positions, return them to the factory setting and start over. Our adjustment guide covers the right way.

5. 5

   Cause 5: Pressure drops to zero before the pump starts

   This one fools people. The water stops at the tap for a moment, then the pump kicks on. Boshart says that's usually a tank pre-charge set too close to the switch's cut-in, not a switch problem, and recommends a pre-charge about 15 percent below the cut-in.

6. 6

   Cause 6: The lever switch keeps tripping

   If your switch has a side lever, it's a low-pressure cutoff. Nuisance trips usually mean the tank pre-charge is too close to the cut-in or the pump can't hold pressure during heavy use. See our low-pressure cutoff reset page.

Checks you can do safely

With the breaker off and the cover removed:

• Look for water, rust or insects inside the box. Boshart warns that bugs and debris getting into the switch through unsealed openings create a fire hazard.
• Look for scorched wire ends or loose terminal screws.
• Check the contacts as described above.

With the system drained, check the tank air charge at the valve on top of the tank. If water comes out of the air valve, the tank is finished.

Fixes, by cause

HomeGuide puts a pressure switch replacement at $150 to $200 with labor. If the real problem is the tank, HomeGuide's range for a pressure tank replacement is $800 to $1,500 or more. The step-by-step swap is on our page on how to replace a well pressure switch.

When to call a pro

Call a well contractor or electrician if:

• The contacts are welded or the switch box shows burn marks.
• The pump runs but pressure won't climb, even with a new switch.
• The breaker trips when the switch closes.
• Pressure falls steadily with every faucet closed, which points to a leak or a failed check valve.

A furnace or HVAC "pressure switch stuck open" fault, like the ones on Goodman furnaces, is a different part entirely. Nothing on this page applies to it.