Start by finding where the pressure drop happens

Low water pressure usually comes from one of three places: the supply line from the street, the main shutoff valve in your home, or the pipes and fixtures inside. The fastest way to narrow it down is to check whether the problem is everywhere or just one faucet.

Turn on a faucet in your kitchen, then check a bathroom sink, a shower, and an outdoor hose if you have one. If pressure is low everywhere, the issue is likely before the main shutoff valve — either the municipal supply or your meter. If pressure is low in only one room or one fixture, the problem is in your home's internal plumbing.

Key Takeaways

  • Low pressure everywhere in the house usually points to the main shutoff valve or the supply line from the street, not your internal pipes.
  • Low pressure in one faucet or room usually means a clogged aerator, a closed shutoff valve under that sink, or mineral buildup in that fixture's supply line.
  • The main shutoff valve can be partially closed by accident; turning the handle all the way counterclockwise often restores full pressure.
  • Cleaning or replacing aerators (the screens at faucet tips) fixes low pressure in individual sinks and showers without calling a plumber.
  • If pressure is low everywhere and the main valve is fully open, contact your water company to check the meter and supply line.

Check and adjust the main shutoff valve

The main shutoff valve controls water flow into your entire home. It is usually located where the water line enters the house — in a basement, crawl space, or utility closet near the foundation. The valve handle should point in the same direction as the pipe (parallel to it) when fully open. If the handle is perpendicular to the pipe, it is partially or fully closed.

Turn the handle counterclockwise until it stops. Do not force it. If the handle is already parallel to the pipe and pressure is still low everywhere, the valve may be stuck or partially blocked inside. In that case, contact your water company — they can check whether the problem is on their side of the meter.

Clean or replace faucet aerators for single-fixture problems

An aerator is the small screen at the tip of most kitchen and bathroom faucets. Mineral deposits and sediment clog it over time, restricting flow. If only one faucet has low pressure, cleaning the aerator usually fixes it in five minutes.

Unscrew the aerator by turning it counterclockwise by hand (or use a wrench if it is stuck). Rinse it under running water and use an old toothbrush to scrub away white or brown buildup. If the screen is damaged or heavily clogged, replace it with a new one from a hardware store — they cost two to five dollars and come in standard sizes. Screw the new aerator back on clockwise until snug, then test the faucet.

Look for closed shutoff valves under sinks

Most sinks have individual shutoff valves under the cabinet, one for hot water and one for cold. These are meant to let you stop water to that sink alone during repairs. If someone closed one by accident, that side will have no pressure.

Open the cabinet under the affected sink. You will see two small valves (usually oval or round handles) where the supply lines connect. Turn both handles counterclockwise until they stop. If one was closed, opening it should restore pressure to that faucet. If both are already open and pressure is still low at that sink, the supply line itself may be clogged — see the next section.

Clear clogged supply lines in individual fixtures

If a single faucet still has low pressure after cleaning the aerator and opening the shutoff valves, sediment or mineral buildup is blocking the supply line. You can flush the line by removing the aerator again and running water directly into the faucet for 30 seconds. If that does not help, you may need to disconnect the supply line and flush it from the other end.

Turn off the shutoff valve under that sink. Use a wrench to unscrew the supply line where it connects to the faucet. Hold a bucket underneath to catch water. Turn the shutoff valve back on briefly to flush sediment out of the line into the bucket. Turn it off again, reconnect the line, and test. If pressure is still low, the clog is deeper in the line or at the faucet itself — a plumber can clear it or replace the faucet.

Check for leaks that reduce pressure

A hidden leak in your walls or under the foundation can reduce pressure throughout the house. Look for wet spots on ceilings, walls, or the foundation. Check your water meter: turn off all faucets and appliances, wait 30 minutes, then check the meter again. If the number has changed, water is leaking somewhere.

Small leaks in visible pipes under sinks or in the basement are straightforward to spot and repair. Leaks inside walls or underground require a plumber with leak detection equipment. Call a plumber if you suspect a hidden leak — the longer it runs, the more damage it causes.

Know when to call a plumber

You can handle aerator cleaning and shutoff valve adjustments yourself. If pressure is low everywhere, the main valve is fully open, and the water company confirms the supply line is fine, the problem is likely in your home's main water line or pressure regulator. A plumber can test the regulator (a bell-shaped device near the main shutoff) and replace it if it has failed.

If pressure suddenly drops after construction, an earthquake, or a water main break in your area, call the water company first. They may be flushing the lines or dealing with a break that affects your neighborhood. Once they confirm the supply is normal, a plumber can check your home's internal system.

Frequently Asked Questions

Why is my water pressure low only in the morning?

Morning low pressure often happens because the water company is flushing the main lines or because overnight sediment settles in your pipes. Run cold water from an outdoor faucet for a minute to clear sediment, then check indoor pressure. If it stays low, contact the water company to ask whether they are doing maintenance.

Can a water heater cause low pressure?

Yes. If only hot water pressure is low, the problem is usually the water heater's dip tube (a pipe inside the tank) or sediment buildup in the tank. Cold water pressure should be normal. A plumber can flush the heater or replace the dip tube. If both hot and cold pressure are low, the problem is upstream of the heater.

What does a pressure regulator do?

A pressure regulator is a valve that reduces water pressure from the street (which can be 80 to 100 pounds per square inch) to a safer level for your home (usually 40 to 60 psi). If it fails, pressure drops everywhere. A plumber can test it with a gauge and replace it if needed.

Should I use a whole-house water filter if I have low pressure?

A whole-house filter can reduce pressure slightly because water has to pass through the filter media. If you already have low pressure, adding a filter will make it worse. Fix the underlying pressure problem first, then decide whether a filter is worth the small pressure drop.

How much does it cost to fix low water pressure?

Cleaning an aerator is free. Replacing one costs two to five dollars. Replacing a main shutoff valve or pressure regulator runs 300 to 800 dollars including labor. A plumber's diagnostic visit typically costs 100 to 200 dollars. Start with the free and cheap fixes before calling someone out.