Well pump short cycling: clicking on and off every few seconds

A well pump that clicks on and off every few seconds is short cycling, and it is the single most destructive thing a well system does to itself. The cause is almost always a pressure tank with no air cushion left, or a check valve that lets water drain back down the well. A $600 to $1,500 tank or a $200 to $400 check valve fixes it in one visit, and either one is cheaper than the $1,200 to $3,500 pump it saves.

Check this first (two minutes)

1. Press the air valve on top of the tank with a screwdriver or a tire gauge, with the pump off. Air hissing out is normal. Water coming out means the bladder is ruptured and the tank is finished. That is the whole diagnosis right there.
2. Knuckle the tank top to bottom. Hollow up high and solid low is healthy. Solid all the way up means it is full of water.
3. Watch the gauge with a tap running. A healthy system takes tens of seconds to swing from cut-in to cut-out. A waterlogged tank swings the full range in two or three seconds.
4. Turn the pump off and watch the gauge for ten minutes with everything closed. Pressure that slowly bleeds down with no water being used points at a check valve or a leak, not the tank.

Then turn the well breaker off until someone can get there. Every extra hour of cycling is motor life you are spending.

What is usually wrong

Every number is on the pricing page, and the pressure tanks and switches page walks through sizing.

Why the tank matters more than the pump

A bladder tank is not storage for its own sake. It exists so the motor gets a decent run every time it starts. Sizing is done off the pump’s minimum run time: enough drawdown that a start is followed by a real run, not a blip. When the bladder splits, the usable drawdown falls from tens of gallons to about a cup, and the pump starts and stops on a loop until something gives. A waterlogged tank is one of the most common reasons a submersible dies early.

This is also the most common thing done badly on a replacement job. A crew that puts a new pump on an old tank without checking precharge has just installed a new pump into the exact conditions that killed the last one. Ask any bidder whether the tank, tee, gauge, relief valve, and switch are included, because they are all the same age.

The local angle

Acidic Blue Ridge groundwater, commonly pH 5.5 to 6.5 in the county’s granite and gneiss, works on the steel and brass around the tank. Tank tees corrode, galvanized nipples close up with rust, and the switch’s sensing port plugs with iron sediment. That is why short cycling shows up on twelve-year-old equipment here rather than twenty-year-old equipment in limestone country. Homes on old galvanized tanks in basements around Flat Rock, Laurel Park, and the older streets of Fletcher are typical examples.

Well houses matter too. A tank in an unheated well house at 2,500 feet loses precharge faster through cold cycling and is more likely to have a frozen switch tube in January.

When to call

Today. Not because the house is in danger, but because the pump is. If nobody can come out, shut the well breaker off and run the pump only when you need water. That single step has saved more pumps than any part on the market.

What to expect on the call

Tell us what happened at the air valve, whether pressure bleeds off with the pump off, and roughly how old the tank is. On site a good tech drains the system, reads the precharge cold, checks it against the switch cut-in, tests the check valve by watching the decay rate, and inspects the switch contacts and sensing port. If the tank is done, it is replaced with one sized to your pump, and the tee, gauge, relief valve, and switch go with it. Most short-cycling visits are one trip, and the number is confirmed before the work starts.