Why Is My Water Pressure Low?

Low water pressure is one of the most common plumbing complaints — and the first useful question is whether it affects the whole house or just one fixture. That single distinction points to very different causes.

Common causes

One fixture only: a clogged aerator or showerhead, or a partly closed supply valve under the sink.
Whole house: a failing pressure-reducing valve (PRV), a partly closed main shut-off, corrosion inside older galvanized pipe, or an issue on the municipal supply.
On a well: a waterlogged pressure tank or a pressure switch that needs adjusting.

Quick test: if hot water is weak everywhere but cold is fine, the water heater's shut-off valve or sediment in the tank may be the culprit.

What you can check

Make sure the main shut-off and the fixture supply valves are fully open.
Note whether the drop was sudden (often a valve or supply issue) or gradual (often buildup inside the pipes).

When to call a pro

If pressure is low across the whole house, a plumber can test pressure at the main, check the PRV, and trace where it drops. One tap to call.

Common causes

What you can check

When to call a pro

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