Low Water Pressure:
Common Causes and Fixes

Low water pressure is one of the most common — and most frustrating — plumbing complaints homeowners have. Whether it's a single faucet with barely a trickle or a whole-house pressure problem that makes showering miserable, low water pressure has distinct causes that can usually be diagnosed and fixed methodically. This guide walks through every major cause and what to do about each one.

First: Is It One Fixture or the Whole House?

The first diagnostic step is to determine the scope of the problem. This single distinction rules out most causes:

• One faucet or fixture only: The problem is almost certainly local — a clogged aerator, a partially-closed supply valve, or sediment in the faucet cartridge. Easy fix.
• One area of the house (e.g., only the upstairs bathroom): Suggests a partially closed zone valve, corroded section of pipe, or supply line restriction in that branch.
• Whole house, hot water only: Clogged water heater inlet, failing water heater, or a water softener bypass issue.
• Whole house, all fixtures: Pressure regulator failure, main shut-off partially closed, municipal supply issue, or corroded main supply line.

Cause 1: Clogged Aerator or Showerhead (Single Fixture)

If only one faucet or showerhead has low pressure, the most likely culprit is a clogged aerator — the small screen at the tip of a faucet that mixes air into the water stream. Mineral deposits from hard water accumulate on the aerator screen over time, gradually reducing flow.

How to Fix It

1. Unscrew the aerator from the faucet tip by hand or with pliers (protect with tape to avoid scratching)
2. Soak it in white vinegar for 30–60 minutes to dissolve mineral deposits
3. Scrub gently with an old toothbrush and rinse
4. Reattach and test

For showerheads, the same technique works: unscrew the showerhead, soak it in vinegar, scrub the nozzle holes with a toothbrush or toothpick. If the showerhead is old, calcified, and difficult to clean, replacing it ($25–$80 for a good showerhead) is often the easier path.

Cause 2: Partially Closed Shut-Off Valve

Every fixture and appliance has a local shut-off valve (also called a stop valve) on the supply line. If someone partially closed a valve — during a repair, by accident, or if a child turned it — low pressure results.

Check the shut-off valves under sinks, behind toilets, under the dishwasher, and at the washing machine. Ball valves (quarter-turn) should be fully inline (handle parallel to the pipe). Gate valves (multi-turn, older style) should be turned fully counterclockwise until you feel resistance.

Also check the main house shut-off valve — usually near where the water supply enters the house — and the meter shut-off valve outside. If either was partially closed after a repair and not fully reopened, whole-house pressure will be affected.

Cause 3: Pressure Regulator Failure

Most homes in the U.S. have a pressure reducing valve (PRV) — also called a pressure regulator — installed where the main water line enters the house. Municipal water supply pressure can range from 40–100 PSI; PRVs reduce this to the ideal residential range of 45–65 PSI.

PRVs have a lifespan of 10–15 years and can fail in two ways:

• Failure closed: Pressure drops dramatically at all fixtures — the most common failure mode
• Failure open: Pressure becomes too high (above 80 PSI), which can damage appliances, cause water hammer, and accelerate pipe wear

You can check your home's water pressure with an inexpensive gauge ($10–$15 at any hardware store) that threads onto an outdoor hose bib. If your pressure is below 40 PSI with all faucets off, a failed PRV is a likely culprit.

Fix: PRV replacement costs $200–$400 in parts and labor. This is a job for a licensed plumber — improper installation can leave your home with dangerously high pressure or no pressure at all.

Cause 4: Corroded or Scaled Pipes (Whole House)

In homes with galvanized steel pipes (common in pre-1970s construction), the interior of the pipe corrodes over decades, creating a thick layer of rust and mineral buildup that dramatically reduces the effective pipe diameter. A pipe that started at ¾-inch inside diameter can be reduced to less than ¼ inch with heavy corrosion — slashing water flow.

Signs of corroded pipes include:

• Low pressure that has gradually gotten worse over years (not a sudden change)
• Rusty or discolored water, especially when you first run hot water
• Pipes that are visibly rusty or corroded on their exterior
• Home built before 1970 with original plumbing

Fix: Unfortunately, corroded galvanized pipes can't be cleaned — they need to be replaced. This is a re-pipe job, typically $4,000–$10,000 for a whole-house re-pipe, and is one of the most impactful plumbing investments you can make in an older home. Learn more about your pipe options in our copper vs. PEX piping comparison guide.

Cause 5: Water Heater Issues (Hot Water Only)

If you have low pressure only from hot water taps, the water heater is likely involved:

• Sediment buildup in tank: Sediment accumulates in tank water heaters and can restrict flow through the outlet
• Partially closed water heater shut-off valve: Check the cold water inlet valve at the top of the water heater
• Water softener or filter problems: If you have a water softener on the cold supply to the water heater, a clogged filter or bypass valve issue can restrict hot water pressure
• Flexible connector crimp or kink: The flexible connectors at the top of the water heater can crimp or develop mineral buildup at the connectors

If flushing the water heater (which every tank unit should have done annually) doesn't improve hot water pressure, have a plumber inspect it.

Cause 6: Municipal Supply Issues

Sometimes the problem is outside your home entirely. Municipal water pressure can drop during peak demand times (mornings, evenings), during work on water mains, or if there's a break in a neighborhood supply line.

How to check: Ask neighbors if they're experiencing the same issue. Contact your water utility to ask about supply pressure in your area and whether any maintenance is being performed. If pressure is consistently low at the meter, you may need to address this with your water utility — or install a booster pump if the utility won't (or can't) increase supply pressure.

Cause 7: Slab Leak or Underground Pipe Leak

A leak in your main supply line — whether inside the slab or underground between the meter and your house — will cause whole-house pressure drop because water is escaping before it reaches your fixtures. Signs include:

• Low pressure that appears suddenly, not gradually
• Water meter spinning even when all fixtures are off
• Unexplained wet spots in the yard
• Hot spots or warm areas on concrete slab floors (slab leak on hot line)
• Higher-than-normal water bills

If you suspect a slab leak or underground line leak, stop reading guides and call a plumber immediately. Learn more in our article on signs of a slab leak and what to do.

DIY Fixes vs. When to Call a Plumber