Why Is My Water Pressure So Low?

Weak flow at the tap is annoying, but it’s also a useful clue — where the drop shows up tells you a lot about the cause. Here’s how to narrow it down before calling anyone.

Start with scope: one fixture, or the whole house?

If pressure is low at a single faucet or shower, the cause is usually local — a clogged aerator or shower head, or a partly closed fixture valve. If it’s low throughout the entire home, the cause is upstream: the main line, the pressure regulator, or the municipal supply itself.

Common causes at a single fixture

• Mineral buildup in the aerator or shower head — common with hard water, and an easy fix by cleaning or replacing the part.
• A partially closed valve under the sink or at the fixture.

Common causes throughout the home

• A failing pressure regulator, if your home has one — it can wear out and restrict flow more than it should.
• Corrosion inside older pipes, which narrows the interior diameter over years.
• A hidden leak diverting water before it reaches your fixtures.
• A partially closed main shutoff valve, sometimes left that way after previous work.
• A municipal supply issue, which is worth ruling out with a neighbor or the water utility.

When it’s worth a professional look

If cleaning an aerator or checking valves doesn’t explain it, especially if the drop was sudden, it’s worth having it checked — a hidden leak or corroding pipe is a problem that gets more expensive to ignore. A plumber can test your pressure and trace it back to the actual source.