Short answerLow water pressure is usually caused by a clogged aerator or showerhead (one fixture), a partly closed valve, a failed pressure-reducing valve, corroded galvanized pipe, a leak, or low pressure from the water supplier. Checking whether one fixture or the whole house is affected narrows it down quickly.
Troubleshooting decision tree
- Is it one fixture? Clean the aerator or showerhead and check the fixture's shutoff valves.
- Is it only hot water? Look at the water heater: its shutoff valve, sediment, or the fixture's mixing cartridge.
- Is it the whole house? Confirm the main shutoff is fully open.
- Measure pressure at a hose bib with a gauge. Many homes are comfortable between 40 and 80 psi.
- If you have a pressure-reducing valve and pressure is low, it may have failed.
- Do a meter test for leaks.
- If pressure is low and the home has galvanized pipe, corrosion is a likely cause.
- Ask neighbors or the utility whether street pressure is low.
Low pressure versus low flow
Static pressure is measured with no water running. Flow is how much water you get when a fixture is open. Corroded pipe often shows normal static pressure but poor flow, because the narrowed pipe restricts how much water can move.
When it's urgent
- Pressure drops suddenly throughout the house and you hear running water (possible break)
- The water meter spins with everything off
Frequently asked questions
Can a water softener cause low pressure?
A clogged or undersized softener or filter can reduce pressure. Test by putting the system in bypass mode.
Why is my pressure fine in the morning but low in the evening?
Neighborhood demand affects street pressure, especially during peak use. Measuring at different times helps confirm.
