Low Water Pressure
Updated February 20, 2026
Could be a clogged aerator or partially closed valve (five-minute fix), or a failing PRV, corroded pipes, or municipal issue. First step: is it one fixture, one area, or the whole house?
Overview
One of the most common complaints and one of the most misdiagnosed. Normal residential pressure is 40-80 PSI, ideal is 50-60. Below 40 feels weak. The diagnostic question: one fixture, one area, or the whole house? That answer narrows the cause dramatically and tells you whether this is a five-minute fix or a plumber call.
Symptoms
- Weak stream even with the handle fully open
- Shower feels like a trickle instead of a full spray
- Washing machine or dishwasher taking much longer to fill
- Multiple fixtures weak simultaneously -- whole-house issue
- Pressure dropped after recent plumbing work -- valve or debris
- Low on hot side only -- water heater or hot shutoff valve
Common Causes
- Clogged aerator -- mineral deposits, rust, and debris accumulate in the screen at the faucet tip. Most common cause at a single faucet, easiest fix.
- Partially closed valve -- after plumbing work, valves get left not fully open. Quarter turn from full open reduces pressure noticeably.
- Debris in the cartridge -- after plumbing work or water main breaks, sediment washes in and lodges in the cartridge or valve body. Restricts that specific fixture.
- Failing PRV -- sticks partially closed, reducing pressure throughout the house. Bell-shaped brass fitting on the main line near the shutoff.
- Corroded galvanized pipes -- internal diameter shrinks from scale and corrosion over decades. Progressive, eventually needs a repipe.
- Municipal issue -- water main break, hydrant flushing, or high-demand period. Not your plumbing. Check with neighbors.
What You'll Need
How to Fix It
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Determine If the Problem Is Localized or Whole-House
Test every fixture: kitchen, bathroom, tub, shower, hose bibs. Hot and cold at each. One fixture? Problem is local (aerator, cartridge, shutoff valve). Multiple or whole house? Upstream issue (main shutoff, PRV, or supply). Hot side only? Water heater valve or the heater itself.
Tip: Check with neighbors. They have low pressure too? Municipal issue. Call your water utility. -
Clean or Replace the Aerator
Single faucet? Aerator first. Unscrew from the tip (tape under pliers to protect the finish). Disassemble: housing, restrictor disc, mesh screen. Rinse, scrub with a toothbrush. Heavy buildup: vinegar soak 30-60 minutes. Damaged screen? Replace the whole aerator ($3-8).
Tip: Before reinstalling, run the faucet without the aerator. Strong pressure? Aerator was the problem. Still weak? Issue is in the cartridge or supply line. -
Check All Shutoff Valves
Every valve in the path, fully open. Main shutoff: counterclockwise for gate, in line with pipe for ball. Meter valve at the street if accessible. Individual shutoffs under the affected fixture. Hot-side issue? Cold inlet valve on the water heater. Even slightly closed restricts flow significantly.
Warning: Gate valves (round handle) can break internally if forced. Stuck? Do not force. A plumber can replace with a quarter-turn ball valve. -
Inspect and Clean the Faucet Cartridge
Aerator clean but still weak? Debris in the cartridge. Shutoffs off, handle off, cartridge out (varies by brand). Inspect cartridge and valve body for sediment, mineral chunks, debris. Flush the body by briefly turning the shutoff on with the cartridge removed (towel ready). Clean or replace, reassemble.
Tip: After plumbing work or water main breaks, debris washes into cartridges. Multiple faucets affected? Clean them all, starting closest to where water enters the house. -
Test and Address the Pressure Reducing Valve (PRV)
Whole house low with all valves open? PRV. Bell-shaped brass fitting on the main line. Pressure gauge on a hose bib. Below 40 PSI? PRV needs adjusting or replacing. Adjustment screw on top: clockwise increases, quarter turns, retest. Over 10-15 years old and adjusting does not help? Replacement time.
Warning: Do not go above 80 PSI. Damages fixtures, blows washing machine hoses, triggers the water heater T&P valve. Sweet spot: 50-60 PSI. -
Assess for Corroded Pipes (Older Homes)
Home built before 1970 with gray metal threaded pipes? Galvanized steel. Magnet sticks to galvanized, not to copper or PEX. Internal corrosion narrows the pipe over decades -- no fix other than repipe. Plumber can assess with a pressure test and camera inspection to determine targeted replacement versus whole-house.
Tip: PEX is the most cost-effective repipe option. Flexible, corrosion-resistant, significantly cheaper to install than copper.
When to Call a Pro
Call a plumber if adjusting the PRV does not fix whole-house low pressure, if the PRV needs replacement, if galvanized pipes need assessment, if debris from a main break will not flush out, or if pressure fluctuates without explanation. A plumber can do a static pressure test at multiple points to pinpoint where the loss is.
Prevention Tips
- Clean aerators every 3-6 months. Unscrew, rinse, vinegar soak if needed.
- Fully open all valves after any plumbing work. Verify flow before calling it done.
- Whole-house sediment filter on the main line. Catches debris before it reaches fixtures.
- PRV tested every 3-5 years, replaced every 10-15. Wears internally even if it seems fine.
- Hard water? Softener reduces mineral buildup in pipes, fixtures, and water heater.
- After a main break or utility work, run an outside hose bib 2-3 minutes before using indoor fixtures. Flushes sediment before it hits your faucets.