Weak showers and slow-filling tubs are frustrating—and they often signal a fixable plumbing issue rather than "just how the house is." The first step is figuring out whether pressure is low everywhere or only at certain fixtures.
Whole-house vs single-fixture pressure loss
- Everywhere: Points to main supply issues—shut-off valves, pressure regulator, corroded pipes, or municipal supply problems.
- One fixture or room: Often a clogged aerator, failing cartridge, or localized pipe restriction.
- Hot water only: Suggests water heater sediment, a kinked flex line, or a failing shut-off at the heater.
Checks you can do first
- Clean aerators and showerheads. Mineral buildup is the most common single-fixture cause.
- Confirm main and meter valves are fully open. Partially closed shut-offs throttle the whole house.
- Ask neighbors if they notice low pressure—utility work or area supply issues may be temporary.
- Test multiple fixtures at once. Pressure that drops only when several run may mean undersized piping or a failing regulator.
- Inspect visible supply lines for kinks, corrosion, or recent DIY work.
Common causes plumbers find
- Pressure-reducing valve (PRV) failure: Worn PRVs can stick low or fail open, causing swings in pressure.
- Galvanized pipe corrosion: Older homes lose interior diameter as rust builds, especially at horizontal runs.
- Hidden leaks: Split lines or slab leaks reduce pressure while raising your water bill.
- Clogged or failing cartridges: Single-handle faucets restrict flow when internals wear out.
- Water heater issues: Sediment at the tank bottom blocks hot-side flow.
- Shared supply lines: Multi-unit buildings may see pressure drops during peak use.
Typical professional fixes
- Replace or adjust the PRV to target 50–60 psi (check local code limits).
- Repipe sections of galvanized or polybutylene supply lines.
- Flush or replace water heater if hot-side pressure is affected.
- Install a booster pump where municipal pressure is legitimately low and plumbing is otherwise sound.
- Repair leaks found with pressure tests or acoustic detection.
When to call a plumber
- Pressure dropped suddenly house-wide without an obvious valve change.
- You see discolored water, banging pipes, or recurring clogs with weak flow.
- DIY aerator cleaning did not help multiple fixtures.
- Your home has older galvanized plumbing and pressure has worsened gradually.
Final takeaway
Start local—clean aerators and verify valves—then look house-wide if the problem persists. Low pressure rarely fixes itself; a plumber can measure static and dynamic pressure, inspect the PRV, and pinpoint whether you need a simple cartridge swap or a repipe plan.