NH Well Pump HelpWell pump short cycling: what it means and what to do
If you hear the pressure switch click on, the pump hum for a few seconds, then click off and back on again, over and over, your pump is short cycling. It’s easy to get used to the sound, but it isn’t normal, and it can wear out a healthy pump. Here’s how to recognize it, the usual causes, what a homeowner can safely check, and when to call a licensed pro.
First: is it short cycling or running nonstop?
| What you notice | What it usually points to |
|---|---|
| Pump starts and stops every few seconds to a minute; the pressure gauge swings quickly up and down | Short cycling. The system reaches its shut-off pressure almost at once because there’s little stored water. Most often a pressure tank problem (The Well Guide). |
| Pump runs for many minutes and never shuts off; pressure climbs slowly or stays low | Running constantly. The system can’t build pressure, from a leak, stuck check valve, low water level or worn pump. See pump runs but no water. |
A healthy system works like this: the pump starts when pressure falls to the switch’s cut-in setting (commonly 30 or 40 PSI), runs until it reaches cut-out (commonly 50 or 60 PSI), then rests. The gauge should rise steadily, hold when no water is used, and fall smoothly as you use water. A gauge that bounces on and off within seconds indicates short cycling (The Well Guide).
Why it matters
Every start sends a surge of current through the motor, which heats it. Pumps are built for a run followed by a rest so that heat can dissipate. The Well Guide says a pump that would normally last 12 to 15 years can fail within 1 to 3 years under sustained short cycling (The Well Guide). The pressure switch contacts wear faster too (The Well Guide). Since replacing a deep-well pump in our towns often runs into the thousands (see our NH cost guide), fixing short cycling early is usually the cheaper path.
Common causes
| Cause | Notes |
|---|---|
| Waterlogged pressure tank (failed bladder or diaphragm) | The most common cause. Modern bladder and diaphragm tanks typically last about 10 to 15 years. When the membrane fails, water fills the air side, the air cushion disappears and the pump restarts on every small draw (The Well Guide). |
| Low air pre-charge (membrane still intact) | Air slowly escapes over time, shrinking how much water the tank can deliver between starts. The Well Guide recommends a pre-charge 2 PSI below cut-in, measured with the tank empty and the pump off (for example 28 PSI on a 30/50 switch) (The Well Guide). |
| Old galvanized tank losing its air | Older unpainted steel tanks have no bladder, so air dissolves into the water. If the tank keeps losing its charge, it usually needs replacing (The Well Guide). |
| Undersized tank | The tank should store enough usable water for the pump to run at least about a minute per cycle. Only about 25 to 30 percent of a tank’s rated size is usable water between cycles (The Well Guide). |
| Leaking check valve, a plumbing leak, or a faulty pressure switch | Less common causes listed by The Well Guide (The Well Guide). A leaking check valve can let pressure bleed off, so the pump restarts with no water in use (UNL Extension). |
| Water treatment regeneration | Water softeners and iron filters often backwash overnight. If the cycling happens mostly in the small hours, a treatment cycle may be the reason rather than a fault (The Well Guide). |
General guidance only. A licensed pro testing your system is the only way to be sure.
Checks that are safe for a homeowner
Watch and listen
With nothing running in the house, watch the pressure gauge near the tank for a few minutes. If the pump starts again with no water in use, something is letting pressure drop. Note how many seconds each on and off period lasts.
Rule out a running fixture
Check for a running toilet, a dripping outdoor faucet, or a softener or filter in a backwash cycle (The Well Guide).
Tap the tank
Tap the tank from top to bottom with your knuckle. A healthy tank sounds hollow near the top (air) and solid lower down (water). A tank that sounds solid all the way up is likely waterlogged (The Well Guide).
Write it down
Note the tank’s age and size from its label, your switch setting if it’s marked (for example 30/50), when the cycling started and what you heard. That helps a pro diagnose it faster.
What not to do
- Don’t open or adjust the pressure switch. University of Nebraska Extension warns homeowners not to adjust it because it is connected to electric power and could cause serious injury (UNL Extension).
- Don’t ignore it for months. Sustained short cycling shortens pump life (The Well Guide).
- Don’t open the well cap or pull the pump. In New Hampshire, maintenance and repair of wells and pumps must be done by a licensed water well contractor, pump installer, plumber or electrician (RSA 482-B:15).
What a licensed pro may do
A pro will typically check the tank’s air pre-charge with the system drained, test for a failed bladder, check the pressure switch and look for leaks or a bad check valve. If the tank has failed, they’ll usually replace it, often with a new switch and gauge, and can tell you whether a larger tank would cut down on cycling. See pressure tank replacement for typical scope and published cost ranges. If the pump itself is worn out after years of cycling, see repair and replacement.
Hire licensed
In New Hampshire, anyone in the business of installing or replacing a well pump must hold a pump installer license from the NH Water Well Board (RSA 482-B:5). Licensed plumbers and electricians may repair and service pumps, but need a pump installer license to install or replace one (NHDES). Before you hire anyone, ask for the license number and check it on the NHDES license lookup.