Why Is My Well Pump Short Cycling, and Is the Pressure Tank Done?
Short cycling means the well pump clicks on and off every few seconds instead of running a steady stretch. One motor maker’s manual names a waterlogged pressure tank as the most common cause. Every start heats the motor, and motor makers want each run to last at least a minute. Too many starts shorten the life of the pressure switch, relays and capacitors, and can overheat the motor.
The first check is the tank’s air charge, called the pre-charge. Check it with the pump off and the tank drained. Most tank makers want 2 psi below the cut-in, where the pump starts. On a common 40/60 switch, that is 38 psi.
A tank that has lost its air, sounds solid when tapped or spits water at the air valve is waterlogged. A failed bladder, a rusting shell or an air charge that keeps dropping usually means a new tank. National cost guides put a typical replacement at $300 to $1,500 installed.
What does short cycling do to a well pump?
A submersible motor draws a surge of current each time it starts, and that surge becomes heat. An engineer writing in the water well industry’s trade journal calls motor heat the main cause of shortened motor life. Motor makers want a minute of run time per start, or two minutes at 2 horsepower and up.
They cap the starts too. One motor maker lists a maximum of 300 starts a day for a single-phase motor up to 3/4 horsepower. From 1 to 5.5 horsepower, the limit drops to 100.
A pump that restarts every few seconds uses that allowance up fast. Holding starts down is the job of a well pressure tank.
How does a 40/60 pressure switch work with the tank?
On a 40/60 pressure switch, the pump comes on at 40 psi and shuts off at 60. That 20 psi spread is typical, and 20/40 and 30/50 switches are common too.
Between those numbers, the air cushion in the tank pushes water to the house. The water you get between pump starts is the drawdown, and it is far smaller than the tank’s size. One maker’s chart shows a 20 gallon tank giving about 5.4 gallons at 40/60. An 86 gallon tank gives about 23.
Sizing works back from the pump. The trade journal sizes a 10 gallon per minute, 1/2 horsepower pump for 10 gallons of drawdown. That is one minute of pumping. A tank too small for its pump makes it cycle more often, even when nothing is broken.
How do you check a pressure tank’s pre-charge?
Tank makers’ manuals boil down to four steps:
- Turn off the breaker for the pump.
- Open a faucet and let it run until the tank is empty and the gauge reads zero.
- Take the cap off the air valve on top of the tank and read it with a tire gauge.
- Compare the reading to the switch. Most makers want 2 psi below cut-in: 38 psi for 40/60, 28 for 30/50, 18 for 20/40.
One maker of composite tanks calls for 4 psi below cut-in instead, so read the label on yours. Makers say to adjust the charge only at ambient temperature, so wait if the shell is hot from the sun.
Water at the air valve means water has reached the air side, a sign the bladder has torn. Tank makers say not to add air to a tank in service that has lost it. Lost air can mean internal corrosion, and more pressure could rupture the shell, so that tank needs a pro.
What causes short cycling and low pressure?
A motor maker’s troubleshooting chart gives the usual causes.
| What you notice | Likely cause | Usual fix |
|---|---|---|
| The pump clicks on and off every few seconds while water runs | A waterlogged tank that has lost its air | Check the air charge; replace the tank if the bladder failed |
| The pump starts when nobody is using water | A leak, or a check valve that will not hold pressure | Fix the leak or replace the check valve |
| The pressure comes and goes | A tank losing air, or a switch set wrong or failing | Check the pre-charge and switch; replace what failed |
| The pump runs all the time | Welded switch contacts, a leak, a worn pump or low water in the well | A pump service visit |
| Water spits from the air valve | A torn bladder or diaphragm | Replace the tank |
Weak pressure can start below ground too. One motor maker notes that a worn pump looks like a leaky drop pipe or a low water level. Those point to well pump repair. If no water comes at all, start with what to check when the well stops.
When is a well pressure tank done?
A tank is done when it can no longer hold its air or its water:
- Water at the air valve. A diaphragm is not a replaceable part, one national guide notes, and a new bladder means taking the tank apart.
- Rust or water under the tank. One guide reads outside rust as decay inside, and makers say not to add air to a corroded tank.
- Air that has dropped since install. Makers read lost air as a possible sign of internal corrosion.
- Age. National guides put tank life at 5 to 15 years, and hard, mineral-heavy water can shorten it.
A galvanized air-over-water tank has no bladder, so its air slowly dissolves into the water. It needs air added back, or it waterlogs. When one keeps waterlogging or starts to rust, ask about a bladder tank.
Does valley heat matter for a pressure tank?
It does. With no frost to plan around, valley tanks sit above ground on a pad or in a pump house. Fresno’s average July high is about 98 degrees, per the Western Regional Climate Center’s airport records.
One tank maker says to install its tanks where they will not see temperatures above 100 degrees. Others list 120 and 130 degrees, and one asks for an enclosed, well-aired spot away from heat sources.
Direct sun can also heat the pump’s control box until its protectors trip, one motor maker warns. Its fix is shade, airflow or a new spot, which a vented pump house or a shade roof can give.
What does well pressure tank replacement cost?
National cost guides land in different places, so treat these as market numbers, not our price list.
| Source | Tank size or scope | Installed cost |
|---|---|---|
| Home-improvement cost guide, 2025 | Typical range | $800 to $1,500 (average $1,000) |
| Same guide | 20 to 29 gallons | $450 to $1,000 |
| Same guide | 40 to 59 gallons | $600 to $1,600 |
| Same guide | 80 to 99 gallons | $850 to $2,300 |
| Home-services marketplace guide, 2026 | Most homes | $300 to $700 (average $500) |
| National business magazine’s home guide, 2024 | Professionally installed | $700 average, up to $1,100 for 80 gallons |
Labor alone runs from about $100 to $500 or more across these guides. A new pressure switch or gauge adds to the total. One guide notes that cramped, hard-to-reach tanks cost more to swap, and a tight pump house can count.
When should you call Big River Drilling?
Call when the pump clicks on and off, the pressure comes and goes, or the tank starts to rust. Big River Drilling is a licensed C-57 well drilling contractor based in Riverdale, working Fresno, Kings and Tulare counties. We handle pressure tank replacement for bladder and galvanized tanks, plus the switches, gauges and check valves.
Our tank installs sit on concrete pads beside the well head, with the control box close by. If cycling has already worn out the pump, we set a new submersible pump too. We take well and pump calls 24 hours a day, seven days a week. Call or text (559) 867-3806 for a free estimate.