Low pressure is one of the most common complaints in older homes. Sometimes the fix takes five minutes with a toothbrush and vinegar. Other times it points to a pressure regulator near the end of its life, a valve that was never fully reopened after a repair, or the inside of aging pipe narrowing with corrosion and scale.
Start by checking several fixtures, both hot and cold, and both inside and at an outdoor hose bib. The pattern of what is weak and what is normal does most of the diagnosing.
Read the pattern
- IfOnly one faucet or showerhead is weakThenClean or replace that fixture's aerator or showerhead; scale buildup is the usual cause.
- IfOnly the hot water is weak, at several fixturesThenLook at the water heater: a partly closed valve or sediment can restrict flow.
- IfEverything in the house is weak, including outdoor bibsThenCheck that the main shutoff is fully open, then suspect the pressure regulator or the supply line.
- IfPressure drops sharply when two fixtures run at onceThenNarrowed or undersized supply pipe is likely. Ask a plumber to check.
- IfPressure changed suddenly and the meter keeps movingThenA leak may be stealing flow. Run the meter test.
Clean an aerator or showerhead
- Unscrew the aerator.Wrap the tip in a cloth and turn it counterclockwise by hand or with gentle pliers.
- Rinse out debris.Small grit or scale flakes often sit on the screen.
- Soak in vinegar.Let scaled parts soak, then brush and rinse before reinstalling.
- Test again.If flow is still weak with the aerator off, the problem is further back.
Parts that affect pressure
- Pressure regulator
- A bell-shaped valve on the incoming line that lowers street pressure to a steady house pressure. When it wears out, pressure can drop or swing.
- Aerator
- The small screen at a faucet tip that mixes air into the stream and catches debris.
- Galvanized pipe
- Steel pipe coated with zinc, common in older homes. Its inside can narrow with corrosion over decades.
- Pressure gauge
- A gauge that threads onto a hose bib to read the house pressure.
Repair options compared
| Cause | Typical repair | Disruption |
|---|---|---|
| Scaled aerator or showerhead | Clean or replace | Minimal |
| Worn pressure regulator | Replace the regulator | Water off for a short time |
| Partly closed or failing valve | Open, repair or replace the valve | Low |
| Corroded supply pipe | Replace sections or repipe | Can involve opening walls |
Common questions
Can a pressure regulator go bad?
Yes. Like any valve with internal parts, regulators wear out. Symptoms include low pressure, pressure that swings, or noisy pipes.
Does hard water cause low pressure?
It contributes. Scale builds up in aerators, showerheads and sometimes inside older pipe, slowly reducing flow.
Who do I call about street-side pressure?
Contact the City of Fullerton water utility for questions about the meter or the supply to your property.
General information for Sunny Hills, not a quote or professional advice. In an emergency, call 911.