You turn on the kitchen faucet, step into the shower, start the dishwasher — everything drizzles. Weak pressure at one tap is annoying. Weak pressure everywhere points to something wrong upstream.
Whole-house low water pressure almost always traces back to one of seven causes, and a few you can check yourself in under an hour.
Whole-house vs one fixture
First, figure out how widespread the problem is. Turn on faucets in the kitchen, a bathroom, and outside.
If only one faucet is weak, the issue is local — probably a clogged aerator (the small screen on the faucet tip), a corroded valve, or a worn cartridge. Unscrew the aerator, rinse it, and reinstall. That often fixes it in minutes.
If every fixture is equally weak — hot and cold, upstairs and down — the problem is upstream in your supply. That is what this guide covers.
Most likely causes
Partly closed main shutoff or meter valve. Every home has two main shutoffs: one near the water meter and one where the supply enters the house. If either was left partly closed after a repair, you will lose pressure everywhere. A ball valve is fully open when the handle is parallel to the pipe; a gate valve needs to turn counterclockwise until it stops.
Failing pressure-reducing valve (PRV). Most homes built after the mid-1980s have a PRV — a bell-shaped brass fitting on the main line. It steps down high municipal pressure to a safe household level. The EPA WaterSense Technical Reference Manual recommends 45 to 60 psi for residential service. When a PRV's spring and diaphragm wear out, pressure drifts too low house-wide. Warning signs: gradual worsening over months, wild fluctuations when multiple fixtures run, or hissing from the valve.
Clogged or corroded galvanized pipes. Galvanized steel was standard before the mid-1960s. Internal rust and mineral scale slowly narrow the pipe over decades. Pressure declines a little more each year until the pipe is replaced — cleaning does not fix it.
Water softener issue. NSF standards allow up to 15 psi of drop across a softener. A unit clogged with iron or experiencing resin failure can restrict flow far more. Bypass it temporarily using the three-valve bypass and retest. Pressure bounces back? The softener is the culprit.
Hidden leak. A pipe leaking under a slab, inside a wall, or between the meter and house bleeds pressure away. Turn off all water and watch the meter. If the dial or leak-indicator triangle is still moving, water is going somewhere it should not.
Municipal supply or peak demand. City pressure drops during morning shower peaks and afternoon lawn-watering. Call your utility to confirm street pressure at your meter. Normal street pressure but low indoor pressure means the problem is inside your home.
Clogged whole-house filter. A loaded sediment cartridge can cut pressure 20 to 30 psi. Change it every three to six months.
How to troubleshoot it yourself
Test pressure with a gauge. A pressure gauge (about $10 to $15 at any hardware store) screws onto an outdoor hose bib. Open it fully and read the dial. Normal is roughly 40 to 60 psi. Test first thing in the morning for the best baseline.
Check both shutoff valves. Confirm the meter valve and house shutoff are fully open. Two minutes, no cost.
Inspect the PRV. Turn the top adjustment screw clockwise in small quarter-turn increments to raise pressure, retesting at the gauge each time. If unsure whether the PRV is at fault, have a plumber test it first.
Ask neighbors and the utility. If nearby homes have the same problem, call the utility — street-level issues are their responsibility.
Replace the whole-house filter cartridge. Shut water off, swap in a matching cartridge, turn water on slowly, retest.
Safety — when to be careful
Pressure that is too high is actually the bigger danger. Most plumbing codes require a PRV where street pressure exceeds 80 psi. Over 80 psi can rupture washing machine hoses, shorten appliance life, and cause leaks throughout the system. If your gauge reads above 80 psi, call a plumber promptly.
Also: corroded gate valves can break if forced. If a shutoff feels stiff, call a plumber rather than muscling it.
When to call a plumber
Call a licensed plumber for PRV replacement (the main line requires permits and specialized fittings), repiping corroded galvanized pipes, a suspected slab or hidden leak (needs detection equipment), well pump or pressure-tank problems, or anything that does not respond to the DIY steps above.
What it typically costs
All figures are 2025-2026 national averages.
PRV replacement: $200 to $700, averaging $400 (HomeAdvisor, July 2025). Complex installations reach $1,200.
Whole-house repipe: $1,500 to $15,000, most homeowners around $7,500 (Angi, March 2026). Labor is roughly 70 percent of total cost. PEX runs $0.40 to $2 per linear foot; copper $2 to $8. Permits add $50 to $500.
Whole-house filter cartridge: $5 to $30 — a DIY swap.
Slab leak detection and repair: $150 to $400 to locate; $500 to $4,000 or more to repair.
Common mistakes
Adding a booster pump before diagnosing just pressurizes the underlying problem. Checking only hot-water pressure misses the main supply — low pressure only on the hot side points to the water heater. Overtightening the PRV screw can spike pressure above 80 psi; make small quarter-turn adjustments and retest each time. Ignoring a slow year-over-year decline almost always means galvanized corrosion is advancing — repiping before failure is far less expensive than after one.
How to prevent it
Have the PRV checked every five to seven years. Swap filter cartridges every three to six months. Test pressure with a gauge twice a year to catch drift early. Budget for a repipe if your home has galvanized pipes. Confirm both main shutoffs are fully open after any plumbing work.
FAQ
What psi is normal for a house? EPA WaterSense recommends 45 to 60 psi. Most codes accept 40 to 80 psi as the safe range. Below 40 psi and flow suffers; above 80 psi and pipes and appliances are at risk.
Can low water pressure damage my home? The pressure itself rarely does, but the cause can. Hidden leaks cause water damage and mold; corroded pipes can burst; a PRV drifting high can spike to dangerous levels. Get to the root cause.
How long does a PRV last? Most last 10 to 20 years. Hard water shortens that. If yours is over 15 years old and pressure is sliding down, have a plumber test it.
Will a water softener always lower my pressure? A well-maintained softener only drops pressure 5 to 15 psi — barely noticeable. A clogged or failing unit can drop far more. Bypass it temporarily and retest to isolate its effect.
How do I know if I have galvanized pipes? Galvanized steel looks dull gray with threaded fittings; copper is reddish-orange; PEX is flexible colored plastic. If your home predates 1960 and has never been repiped, galvanized is almost certain.
Start with the simple checks — pressure gauge, shutoff valves, filter cartridge. If those do not solve it, bring in a licensed plumber to test the PRV, check for leaks, and assess your pipes before a small problem becomes a large one.
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Sources
- EPA WaterSense. "Service Water Pressure — Technical Fact Sheet." EPA-832-F-23-016, July 2023. epa.gov
- DOE Building America Solution Center (PNNL). "Service Water Pressure." basc.pnnl.gov
- HomeAdvisor. "Water Pressure Regulator Replacement Cost [2025 Data]." Updated July 29, 2025. homeadvisor.com
- Angi. "Cost to Repipe a House [2026 Data]." Updated March 17, 2026. angi.com
- Dierolf Plumbing. "Low Water Pressure on City Water: 7 Common Causes." dscwater.com
- City of Portland Bureau of Water Works. "Troubleshooting Water Pressure and Flow." portland.gov
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