Short Cycling: The Cheap Fault That Kills Well Pumps

A pump that clicks on and off every few seconds is not a pump problem yet. Left alone for a few months, it becomes one, and the repair goes from a few hundred dollars to a few thousand.

Stand next to your pressure tank with every tap in the house turned off. If you can hear the pump clicking on and off every few seconds, stop reading, and book somebody, because that sound is costing you money right now.

It is called short cycling. It is not a pump fault. It is the tank behind the pump failing to do its job, and the pump is the thing that pays for it.

The short version. A well pump wears out on starting, not on running. Short cycling can turn a handful of starts an hour into hundreds, which is how a $600 to $1,500 tank problem becomes a $1,600 to $3,800 pump problem.

What the tank is actually for

People assume a pressure tank stores water. It does, but that is not the point of it. The point is the air.

Inside a modern tank is a rubber bladder with water on one side and compressed air on the other. As the pump pushes water in, the air compresses. When you open a tap, that compressed air pushes the water back out. The pump does not need to run, because the air is doing the work.

That is why a healthy system lets you wash your hands without the pump starting at all. The tank covers small draws entirely, and the pump only runs when the tank has given up enough water to drop to the cut-in pressure.

Lose the air and the tank becomes a lump of metal full of water. Now every drop you draw comes straight from the pump, so the pump starts the moment you open a tap and stops the moment you close it.

Confirming it in two minutes

Run a tap at a steady, moderate flow and listen.

Healthy: the pump starts, runs for a good while, stops. It might not start at all for a short draw.

Short cycling: the pump starts, runs for a few seconds, stops, and starts again almost immediately. The pressure gauge swings up and down with it, rapidly.

A second check: tap the side of the tank from the bottom upward with a knuckle. A healthy tank sounds solid low down where the water is and hollow higher up where the air is. A waterlogged tank sounds solid all the way up, and feels unusually heavy.

The three causes

The tank has lost its air charge. The most common, and the best news. Air escapes slowly through the valve or gets absorbed over years. If the bladder is intact the tank can be drained and recharged, and that can be the entire repair.

The bladder has ruptured. Then air and water are in contact and no recharge will hold. The tell is water spitting out of the air valve on top when you press it. That tank is finished, and a replacement is $600 to $1,500. See pressure tank installation and replacement.

The tank is simply too small. Less common but it happens, usually where somebody bought on price. An undersized tank gives the pump too little to work with and short cycles from day one, quietly shortening the pump’s life for years.

There is a fourth possibility worth ruling out: a failed check valve letting pressure bleed back down the well, which makes the pump restart for nothing. That one sits on the pump side. See well pump repair.

Why we treat this as urgent

Most plumbing faults get worse slowly and cost the same to fix whenever you get to them. This one is different, because the damage is happening to a different component than the one that failed.

Every start pulls a heavy inrush of current through a motor sitting at the bottom of a well. A pump designed for a certain number of starts over its life gets through them at many times the intended rate. Then it fails, the symptom is no water, and the diagnosis is a pump replacement.

That pump did not wear out. It was worn out by a tank that could have been fixed for a fraction of the cost.

So when somebody tells us their pump is noisy or clicky but the water is still fine, we do not tell them to wait and see. We tell them this week. The price comparison makes the argument better than we can.

What we do about it

Test the air charge against your switch settings, check the bladder, check the gauge, and check the switch and check valve while we are there, because a dead gauge hides every other fault on the system.

If it is an air charge, that is the repair. If it is the bladder, you get told the tank is finished and why. If it is the switch, that is $250 to $450. We diagnose before we quote, which on a well system is the difference between a few hundred dollars and a few thousand.

See pressure tank repair, or well pumps and pressure tanks for how the pieces fit together.

What is short cycling?

A pump switching on and off rapidly, often every few seconds, instead of running for a minute or two at a time. It means there is nothing holding pressure between pump starts, which is the pressure tank’s whole job.

Why is short cycling so bad for a pump?

Motors wear on starting, not on running. A pump that should start a handful of times an hour and instead starts hundreds of times gets years of wear in months, and then fails in a way that looks like a pump problem rather than a tank problem.

Can I fix short cycling myself?

You can confirm it, which is genuinely useful. Setting the air charge correctly has to be done against the switch settings with the system drained, and getting it wrong makes things worse, so it is worth having done properly.

What does it cost to fix?

If the tank has simply lost air, recharging it can be the whole repair. A pressure switch is $250 to $450. If the bladder has ruptured the tank is finished and a replacement is $600 to $1,500. All of which beats $1,600 to $3,800 for the pump it would have taken out.

How long can I leave it?

Do not. This is the one plumbing fault on a well system where waiting reliably multiplies the bill.

Written by the team at Shoresteady Plumbing, Temperanceville, Virginia. Master plumbing licensed in Virginia and Maryland. Prices shown are typical ranges for the Eastern Shore, not a quote. Your written estimate is the only number that binds either of us.

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