Low Water Pressure? How to Diagnose and Fix It
1. Diagnose: Is It the Whole House or Just One Fixture?
| Pattern | Likely Cause | Fix |
|---|---|---|
| Low at ONE faucet only | Clogged aerator or supply valve | Clean aerator — free |
| Low at ALL fixtures, hot and cold | PRV failing, main valve, or pipe issue | See fixes below |
| Low only on HOT water | Water heater valve partially closed | Open valve fully |
| Pressure drops when multiple fixtures run | Undersized supply line or PRV | PRV replacement |
| Old home, gray steel pipes visible | Galvanized pipe corrosion | Repiping needed |
2. Fix #1: Clean Faucet Aerators (Free, 5 Minutes)
Start here, especially if only one or two fixtures are low.
- Unscrew the aerator from the faucet tip (by hand or with pliers + cloth to avoid scratching).
- Rinse out sediment and mineral buildup.
- Soak in white vinegar for 30 minutes if heavily crusted.
- Reinstall and test.
3. Fix #2: Check the Main Shutoff Valve
If someone recently did plumbing work, the main valve may not have been fully reopened.
- Find the main shutoff (usually near the water meter, in the basement, or outside).
- Gate valve (round handle): Turn fully counterclockwise until it stops.
- Ball valve (lever handle): Handle should be parallel to the pipe (perpendicular = closed).
4. Fix #3: Replace the Pressure Reducing Valve (PRV)
This is the most common cause of gradual whole-house pressure loss. PRVs fail after 7–12 years.
The PRV is a bell-shaped brass valve on your main water line, usually right after the meter or shutoff.
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Get Your Free Diagnosis5. Parts You Might Need
Watts 3/4" Pressure Reducing Valve — ~$40 — View at Home Depot
Water Pressure Test Gauge — ~$10 — View at Home Depot
Normal home water pressure: 40–60 PSI. Below 30 = too low. Above 80 = too high (damages fixtures).
6. Cost Breakdown
| Option | Cost | When |
|---|---|---|
| Clean aerators / open valve | $0 | Single fixture or valve issue |
| DIY PRV replacement | $40–$60 | Gradual whole-house loss |
| Plumber — PRV replacement | $200–$500 | Same fix, pro does it |
| Whole-house repiping | $4,000–$10,000 | Corroded galvanized pipes |
7. When to Call a Plumber
- You've checked aerators, valves, and PRV but pressure is still low — could be a supply line issue from the street.
- You have galvanized steel pipes (gray, magnetic) — repiping is the only real fix.
- Pressure drops suddenly (not gradually) — could be a leak or water main break in your area.
- You're not comfortable working on the main water line.
FAQ
What causes low water pressure in a house?
Most common: failing PRV (pressure reducing valve), clogged aerators, partially closed main valve, or corroded galvanized pipes in older homes.
How do I test my water pressure?
Screw a water pressure gauge ($10) onto an outdoor hose bib. Turn on fully. Normal is 40–60 PSI. Below 30 = problem.
Can a water heater cause low pressure?
Yes, but only on hot water. If cold pressure is fine but hot is weak, the water heater shut-off valve may be partially closed, or sediment has built up in the tank.
Frequently Asked Questions
What causes low water pressure in an entire house?
Common causes: partially closed main shutoff valve, failing pressure regulator, corroded galvanized pipes, or a municipal supply issue. Check with neighbors first. If they have normal pressure, the problem is in your plumbing.
How do I fix low water pressure myself?
First, check that the main shutoff valve is fully open. Then check the pressure regulator (usually near the main shutoff). If you have old galvanized pipes, corrosion buildup is likely the cause and requires pipe replacement.
Related Guides
How to Unclog a Toilet (When a Plunger Doesn't Work)How to Unclog a Drain Without Calling a PlumberHow to Fix a Leaking Faucet (Kitchen & Bathroom DIY Guide)How to Fix a Running Toilet (Step-by-Step DIY Guide)Not sure which parts to buy?
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