Why Your Water Pressure Is Low — Causes & Fixes

Why is my water pressure so low and how do I fix it?

Low water pressure usually traces to a clogged aerator or fixture, a partly closed shutoff valve, a failing pressure regulator, or buildup in old galvanized pipes. Start with the cheap, single-fixture checks before assuming a whole-house problem.

ℹ️ Reference only: For general reference only. This guide does not guarantee any result — every home is different. Verify against your local building codes and a licensed professional before acting, especially for electrical, gas, plumbing, structural, or roof work.

💵 DIY: aerator cleaning $0; new aerator/showerhead $8–$30; pressure gauge $10–$15; filter cartridge $15–$40. Pro: PRV replacement $350–$600; hidden leak detection $150–$400 plus repair; water heater flush $100–$200; whole-house repipe $4,000–$15,000+ depending on size and material. ⏱ 15–30 minutes for aerator cleaning and valve checks; about an hour for a pressure test and leak check; a PRV replacement or repipe is a half-day to multi-day pro job. ● Use caution

Safety: Plumbing work risks water damage: know where your main shutoff is and use it before opening any line. Never set whole-house pressure above 80 psi — it stresses fixtures, hoses, and the water heater's relief valve. Before flushing a water heater, turn off its power at the breaker (electric) or set the gas control to pilot, then let it cool and shut the cold supply — draining while powered can dry-fire and ruin the element, and the water is hot enough to scald. Stop and call a pro if you find a hidden leak, are working near a gas line, or aren't comfortable with the water heater.

Common causes

Clogged faucet aerator or showerhead — mineral scale and debris choke the tiny screens at the tip of the fixture. This is the #1 cause of low flow at one specific faucet. (most common)
Quick check: Is it only one faucet/shower? Unscrew the aerator or showerhead; if flow jumps when removed, the screen is clogged.
Partially closed shutoff valve — the main shutoff, the meter valve, or a fixture's angle-stop got bumped or was never fully reopened after a repair. (most common)
Quick check: Find the main shutoff (near where water enters the house) and any under-sink stops; make sure each is turned fully open (counterclockwise / handle inline with the pipe).
Failing or misadjusted pressure-reducing valve (PRV) — the bell-shaped regulator near the main line drifts over time and can drop whole-house pressure. Typical lifespan is roughly 10–15 years. (common)
Quick check: Is the WHOLE house weak? Screw a $10 pressure gauge onto an outdoor hose bib; normal is 45–60 psi. Below ~40 psi house-wide points at the PRV (or the city supply).
Clogged or corroded galvanized steel pipes — older homes (commonly pre-1970) build up internal rust/scale that narrows the pipe bore and slowly strangles flow. (common)
Quick check: Old house with steel pipes and pressure that's been declining for years, worst at the farthest fixtures? Likely internal corrosion.
Municipal supply issue or shared peak demand — utility work, a water main break, or everyone in the neighborhood using water at the same time. (common)
Quick check: Ask a neighbor if theirs is low too, or check the utility's outage page. If it's the whole street, it's not your house.
Clogged whole-house water filter or softener — a spent cartridge or fouled softener resin restricts flow to everything downstream. (less common)
Quick check: Got a filter housing or softener? Note the install date; put it on bypass temporarily — if pressure returns, the filter/softener is the choke point.
Water heater issue — only hot-water pressure is weak, from sediment, a partly closed heater shutoff, or clogged hot-side aerators. (less common)
Quick check: Is only the HOT side weak at multiple fixtures? Points at the heater or its supply valve.
Hidden leak in a supply line — a slab or wall leak bleeds off pressure and wastes water. (less common)
Quick check: Shut every fixture, then watch the water meter for 30–60 min. If the dial moves with everything off, you likely have a leak.

How to fix it

Isolate the problem first: is it one fixture or the whole house, hot-only or both? This single question tells you whether to clean a fixture (cheap) or chase a system issue.
Clean the aerator: unscrew it from the faucet tip by hand (or wrap with tape and use pliers to avoid scratching), rinse the screens, soak in white vinegar for a few hours to dissolve scale, then reassemble. Do the same for a showerhead.
Verify every shutoff is fully open: the main shutoff near the meter or where the line enters the house, plus the angle-stops under each affected sink/toilet. Turn fully counterclockwise.
Test whole-house pressure with a screw-on gauge at an outdoor hose bib. 45–60 psi is the healthy range; above 80 psi is too high and damages fixtures, below ~40 is too low.
If a PRV is present and pressure is low everywhere, you can try adjusting it: loosen the lock nut and turn the top bolt clockwise a little to raise pressure, re-checking the gauge after each small turn — never go above 80 psi. If turning it does nothing, the PRV has failed and needs replacement (a pro job in many areas).
Replace or bypass a spent whole-house filter cartridge per the manufacturer's schedule (typically every 3–6 months).
Flush the water heater only if the hot side alone is weak: first cut power (electric breaker) or set gas to pilot, then let the tank cool and shut off its cold-water supply before draining a few gallons from the drain valve — draining a powered or full-hot tank risks a burned-out element and scalding. Follow your heater's manual; if unsure, leave it to a pro.
Do the meter test for hidden leaks: with all water off, a moving meter means a leak — call a plumber to locate it.
If old galvanized pipes are the cause, there's no lasting DIY fix — re-piping the house in copper or PEX is the real solution and is a licensed-plumber job.

DIY or call a pro?

DIY is fine for cleaning aerators and showerheads, opening shutoff valves, swapping a whole-house filter, testing pressure with a gauge, and the meter leak test. Call a licensed plumber for replacing a failed pressure-reducing valve, diagnosing/repairing hidden or slab leaks, repiping corroded galvanized lines, and any water-heater work you're not comfortable with — these involve soldering, gas, electrical, or risk of flooding.

Tools & parts

Adjustable wrench or channel-lock pliers
White vinegar (for soaking scale)
Old toothbrush or small brush
Screw-on water pressure gauge
Plumber's tape (Teflon tape)
Replacement aerator/showerhead or filter cartridge (if needed)
Flashlight

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Based on: Reputable DIY references (This Old House, Family Handyman, Bob Vila in spirit); Manufacturer guidance for faucets, pressure-reducing valves, and water heaters; Plumbing-code norms for residential service pressure (typical 45-60 psi, 80 psi max)

This is general guidance, not a substitute for professional diagnosis. Plumbing systems and local codes vary; when in doubt or when work involves gas, electrical, hidden leaks, or repiping, consult a licensed plumber.