Low water pressure on a well

Several different problems produce this same symptom, and they need completely different fixes. Work down the list — each one names the check that rules it in or out.

1. 1

   The pressure switch setting

   The switch decides at what pressure the pump starts and stops. Many are set to 30/50 psi when the house would be more comfortable at 40/60. Nothing is broken; the system is simply set low.

   How to tell
   Pressure is consistently mediocre rather than variable, and has been as long as you can remember. The switch cover is stamped with its setting.

2. 2

   A clogged sediment filter

   The single most common cause of pressure that has got worse over weeks, and the cheapest to fix. A cartridge filter doing its job eventually blocks, and pressure falls off as it does.

   How to tell
   Pressure has declined gradually since the filter was last changed, and it affects the whole house. Removing the cartridge temporarily restores pressure immediately.

3. 3

   A pressure tank that has lost its air charge

   The tank stores pressurised water using an air cushion. If the pre-charge leaks away or the bladder fails, usable storage collapses and the pump cycles rapidly to keep up.

   How to tell
   The pump switches on and off every few seconds during steady use. Tapping the tank sounds solid near the top rather than hollow.

4. 4

   A failing pump, or a falling water table

   Pumps wear out and lose output; water tables drop in dry spells, leaving the pump drawing from a lower and sometimes siltier level. These are the expensive causes and the reason to eliminate the cheap ones first.

   How to tell
   Pressure that fades during heavy use and recovers after a rest, spitting taps, or cloudy water appearing alongside the pressure drop. Worse in dry seasons points at the water table.

5. 5

   Scaled or corroded galvanised pipe

   Old galvanised plumbing narrows internally over decades as it corrodes and scales. The pressure at the wellhead is fine; what reaches the tap is not.

   How to tell
   An old house with galvanised pipe, pressure that is worst at the furthest or highest fixtures, and good pressure at an outside spigot near the supply.

The reason to work in this sequence is purely financial. The cheap causes are also the common ones, and every year people replace pumps that were working perfectly because nobody checked a twenty-dollar filter cartridge first.

1. Read the pressure switch cover. If it says 20/40 and the house feels weak, that alone may be the answer.
2. Change or remove the sediment filter cartridge. If pressure returns, you have found it.
3. Watch the pump during steady water use. Rapid on-off cycling means the pressure tank has failed.
4. Check the tank's air pre-charge with a tyre gauge on the schrader valve, with the system depressurised. It should read 2 psi below the cut-in pressure.
5. Only now consider the pump and the well itself. If pressure fades during long use and recovers after a rest, suspect the water table or the pump.

This is a common question and it deserves a straight answer with the caveats attached, because it involves mains voltage and a pressurised system.

Inside the switch cover are two nuts. The larger one raises or lowers both cut-in and cut-out together, keeping the 20 psi span. The smaller one changes only the cut-out, widening or narrowing the span. Turning the large nut clockwise raises the pressure range.

Two limits are worth respecting. Most residential systems should not be pushed beyond 60 psi cut-out, because fixtures, appliances and older pipe are not designed for it, and a burst supply hose costs far more than the comfort was worth. And whenever you change the switch setting, the pressure tank's air pre-charge has to be reset to match — 2 psi below the new cut-in. Skip that and you have just recreated the short-cycling you were trying to avoid.

• Kill the breaker before removing the switch cover. There are live mains terminals inside it.
• Adjust in small increments, a turn or two at a time, and let the system cycle between changes.
• Do not exceed 60 psi cut-out on a normal residential system.
• Always reset the tank pre-charge to 2 psi below the new cut-in afterwards.
• If you are not comfortable working near live terminals, this is a small job for a well contractor.

Check your tank is sized for your pump→

Low pressure on hot taps alone rules out everything above — the well, the pump, the pressure tank and the main supply are all shared by both.

The usual causes are sediment built up in the bottom of the water heater, a partially closed shut-off valve on the heater's cold inlet, or scale blocking the outlet nipple. On tankless heaters, scale in the heat exchanger is the common one and it needs descaling on a schedule in hard water.

Flushing the tank is the first thing to try and costs nothing but time.

If this turns out to be the cause, here is where the equipment sits in the treatment train. Order matters — each stage protects the one after it.

1. 1
   Sediment pre-filterFirst, where the line enters the houseProtects everything downstream from grit and silt. Cheap to replace, and it is the stage that keeps the expensive stages alive.

Enter your test results for a train built around your water→