Well pumps · troubleshooting
Low water pressure on a well: a troubleshooting order
Weak showers on a well can come from a clogged filter cartridge or a pump that is wearing out, and guessing wrong gets expensive. Work from the cheapest, most common causes to the most expensive, and read a pressure gauge at each step so you know what changed.
Step by step
- Is it one fixture or the whole house? Low flow at one faucet or shower is usually a clogged aerator or showerhead, not the well.
- Read the gauge while water runs. Open a tap and watch the gauge by the pressure tank. Note the cut-in (where the pump starts) and cut-out (where it stops). A common residential setting is 40/60, but check your switch. If the gauge is old or stuck, replace it — a 0–100 psi gauge with a 1/4″ NPT fitting is the usual size.
- Check filters and treatment. A clogged sediment cartridge, a fouled softener, or an iron filter that needs backwashing all drop pressure after the tank. If pressure is normal at the tank but low at the taps, put the system in bypass and see if it recovers. See Waterdrop whole-house filters for cartridge-based systems.
- Check the pressure switch. Pitted contacts or a clogged pressure-sensing port can make the pump stop early. See replacing a 40/60 pressure switch.
- Check the pressure tank. A waterlogged tank or wrong precharge causes pressure swings and rapid cycling. See pressure tank precharge and well pump short cycling.
- Look for leaks. A running toilet, a leak in the yard line, or a failing check valve can keep the system from building pressure.
- Then the pump and the well. If the pump runs and runs but cannot reach cut-out, the pump may be worn, the drop pipe may be leaking, or the well may not be keeping up (especially in dry weather or after heavy use). That needs a licensed well contractor to test.
What the gauge tells you
| Gauge behavior | Most likely area | Next step |
|---|---|---|
| Normal at the tank, low at taps | Filters, softener, fixtures, or undersized piping | Bypass treatment, change cartridges, clean aerators |
| Swings fast between cut-in and cut-out | Pressure tank precharge or waterlogged tank | Check precharge with the pump off and tank drained |
| Pump stops below the set cut-out | Pressure switch or its sensing port | Inspect or replace the switch (power off) |
| Pump runs long and never reaches cut-out | Pump wear, drop-pipe leak, or low well yield | Call a licensed well contractor |
| Pressure slowly drops with no taps open | Leak or a failing check valve | Look for leaks; contractor checks the check valve |
Upgrading for steady pressure
If the pump is due for replacement or the house has outgrown a standard pressure-switch setup, a constant-pressure pump such as the Grundfos SQE keeps pressure steady as more taps open. See SQ vs SQE constant pressure and sizing a well pump by GPM and head. R.E. Merrill & Associates is a Grundfos dealer — ask us about SQ and SQE pumps for your well.
When to call a pro
- The pump runs but cannot build pressure, or you have air or sand in the water.
- Pressure dropped after a dry spell or heavy water use — the well yield needs testing.
- Any work at the wellhead, on the pump, or on the electrical supply.
Start with a licensed well contractor for pump and well diagnosis and a licensed electrician for wiring. R.E. Merrill & Associates has handled industrial and municipal pumps and fluid systems since 1987 and is a Grundfos dealer — contact R.E. Merrill & Associates about Grundfos SQ, SQE, and SP well pumps.
Related across the site
- Iron in well water and softeners — iron fouling is a common cause of pressure loss through treatment
- How to test a sump pump — the other pump in your basement worth checking each season
Sources
- Square D Pumptrol pressure switch instructions — cut-in/cut-out settings and safe service with power off.
- Amtrol Well-X-Trol installation manual — precharge checked with the tank drained and pump off.
- Grundfos SQ/SQE product literature — constant-pressure operation with the CU 301.