Why Is My Water Pressure Low?

Is It One Fixture or the Whole House?

This is the most important diagnostic question. The answer tells you exactly where to look.

One fixture: The problem is at that fixture — clogged aerator, partially closed supply valve, or a blockage in the supply line to that fixture.

Whole house: The problem is in the main supply — shutoff valve, pressure reducing valve, or municipal supply issue.

Hot water only: The problem is related to the water heater — sediment buildup, a partially closed hot water valve, or a failing mixing valve.

One Fixture: Clogged Aerator (2-Minute Fix)

The aerator is the small screen/filter at the tip of your faucet. It mixes air into the water stream to reduce splashing. Over time, sediment, calcium, and debris clog it.

1. Unscrew the aerator from the faucet tip (counterclockwise — you may need pliers with a cloth to avoid scratching the finish)
2. Disassemble the screen parts and rinse under water
3. Soak in white vinegar for 30 minutes if there's heavy calcium buildup
4. Reassemble and screw back on

If the pressure is good without the aerator, the aerator was the problem. If pressure is still low without the aerator, the issue is upstream.

One Fixture: Supply Valve or Line

Under every sink, there should be two shutoff valves (hot and cold). Make sure they're fully open — turn counterclockwise until they stop. A valve that's only 80% open restricts flow noticeably.

For showers with no accessible shutoff, the issue might be:

• Clogged shower head — unscrew it and soak in vinegar
• Flow restrictor — many modern shower heads have a built-in flow restrictor that can get clogged
• Cartridge restriction — the shower valve cartridge may be partially clogged with sediment

Whole House: Check the Main Shutoff Valve

Your house has two main shutoff valves:

1. At the meter (usually at the street) — this is the city's valve, but you can check that it's fully open
2. At the house (where the main line enters, usually in the garage, utility room, or near the water heater) — this is yours

Turn the house-side valve fully counterclockwise (gate valve) or parallel to the pipe (ball valve). A partially closed main valve is one of the most common causes of low pressure throughout the house — and one of the most overlooked.

Whole House: Pressure Reducing Valve (PRV)

Many homes have a PRV (also called a pressure regulator) where the main water line enters the house. It looks like a bell-shaped brass fitting on the main line. Its job is to reduce the high pressure from the municipal supply (60-80+ psi) to a safe household level (40-60 psi).

When PRVs fail, they often fail partially closed — dropping your pressure below comfortable levels.

Test: Attach a pressure gauge to a hose bib (outdoor faucet). Normal household pressure is 40-60 psi. Below 40 psi, you'll notice it. Below 30 psi, something is wrong.

The fix: PRVs can sometimes be adjusted (there's a screw on top). Turn it clockwise to increase pressure. If adjustment doesn't help, the PRV needs replacing — this is a $50-$80 part plus $200-$400 in labor.

Whole House: Municipal Supply Issues

If your pressure dropped suddenly and your neighbors report the same issue:

• The city may be doing water main work
• A main break somewhere in the system is reducing pressure
• High demand (hot summer days, everyone watering lawns)

Call your water utility to ask if there are known issues in your area.

Hot Water Only: Water Heater Related

Low pressure from hot taps only points to the water heater:

• Partially closed hot water outlet valve on top of the water heater — make sure it's fully open
• Sediment buildup restricting flow through the tank — flush the tank
• Failing mixing valve — if you have a thermostatic mixing valve, it can restrict flow when it fails
• Cross-connection issue — a failed check valve on a recirculation system can reduce hot water pressure

Sudden Pressure Drop: Emergency Checklist

If pressure drops suddenly and dramatically:

1. Check for a visible leak inside or outside your house (broken pipe, sprinkler line)
2. Check the main shutoff valves
3. Call neighbors to see if it's area-wide
4. Check with the water utility
5. If you can't find the cause and pressure is very low, turn off the main valve and call a plumber — you may have a slab leak or broken pipe underground

When to Call a Professional

• Pressure is low throughout the house after checking valves
• You suspect a PRV failure (pressure gauge reads below 40 psi)
• Pressure dropped suddenly with no obvious cause
• Hot water pressure is significantly lower than cold
• You hear running water when nothing is turned on (hidden leak)

Expect to pay: $80-$150 for a diagnostic visit, $200-$400 for PRV replacement, $150-$500 for valve replacement depending on location and type.