Where low water pressure comes from

Low water pressure usually starts at one of three points: the water main coming into your house, the pipes inside your walls, or the fixtures themselves. The fastest way to narrow it down is to check whether the problem is everywhere or just one sink or shower.

If only one fixture has weak flow, the issue is almost certainly a clogged aerator (the screen at the tap's mouth) or a valve that's partially closed. If the whole house is affected, the problem is either in your main water line, your pressure regulator, or a blockage deeper in your plumbing. If only the hot water is weak, your water heater may be the culprit.

Start by checking your water meter and the main shutoff valve. The meter is usually in a box near the street or in your basement. Look for a small dial or digital display; if it's moving when no water is running, you have a leak somewhere in your line. The main shutoff is typically near the meter or where the line enters your house—make sure it's fully open (the handle should be parallel to the pipe, not perpendicular).

Key Takeaways

  • Check whether low pressure affects the whole house or just one fixture; one fixture usually means a clogged aerator or closed valve, while whole-house pressure points to the main line or pressure regulator.
  • Your main water shutoff valve must be fully open (handle parallel to the pipe) and your water meter should not be moving when no water is running.
  • Sediment buildup in aerators and screens is the most common cause of weak flow and can be cleaned by unscrewing the fixture and rinsing the screen.
  • A pressure regulator that has failed will cause low pressure throughout the house and usually needs replacement by a licensed plumber.
  • If pressure is low only for hot water, flush your water heater's sediment drain valve or call a plumber to drain the tank.

Cleaning aerators and screens

The aerator is the small screen at the end of your faucet. Sediment and mineral deposits collect there and restrict flow. Unscrew it by hand (turn counterclockwise) or use a wrench if it's stuck. Rinse it under running water and use an old toothbrush to scrub away any buildup.

If the aerator is heavily clogged, soak it in white vinegar for 30 minutes, then scrub again. Rinse thoroughly and screw it back on. Do the same for showerheads—unscrew them, clean the screen, and reinstall. This fixes the problem in roughly half of all low-pressure complaints and costs nothing.

Check the screens on any outdoor faucets or hose bibs as well. These collect debris more easily and are often overlooked.

Testing and adjusting your pressure regulator

If the whole house has low pressure and your main shutoff is open, your pressure regulator may have failed. This is a bell-shaped or cylindrical device usually mounted on the main water line just after the shutoff valve. It keeps incoming pressure from the street (which can be 60 to 80 pounds per square inch) at a safe level for your home's pipes, typically 40 to 60 psi.

You can test your pressure with a water pressure gauge, which screws onto any outdoor faucet and costs $10 to $20 at any hardware store. Screw it on, turn the faucet fully open, and read the number. If it's below 40 psi, your regulator is likely failing or set too low.

Some regulators have an adjustment screw on top. Turning it clockwise increases pressure; counterclockwise decreases it. Turn slowly—a quarter turn at a time—and retest. If the gauge still reads low after adjustment, or if you cannot locate the regulator, call a licensed plumber. A failed regulator cannot be reliably repaired and usually needs replacement.

Checking for leaks in your main line

A leak in the water main between the street and your house will lower pressure throughout the home and waste water. To check for a leak, locate your water meter and note the reading. Do not use any water for two hours, then check the meter again. If it has moved, you have a leak.

If you find a leak, you will need a plumber. Main line leaks are underground and require excavation. Call your water utility first—some utilities own the line from the meter to the street and will repair it at no cost. If the leak is on your side of the meter, you are responsible for the repair.

While waiting for a plumber, you can reduce water loss by closing the main shutoff valve. This will cut off water to the whole house, so plan accordingly.

Flushing sediment from your water heater

If only your hot water has low pressure, sediment has likely built up inside your water heater tank. Over time, minerals settle at the bottom and can block the outlet pipe, restricting flow.

Locate the drain valve at the bottom of your water heater (usually in a basement, garage, or utility closet). Attach a garden hose to it and run the hose to a floor drain or outside. Turn off the heater's power or gas, let the water cool for an hour, then slowly open the drain valve. Let water run until it runs clear—this usually takes 10 to 20 minutes. Close the valve, turn the power back on, and test your hot water pressure.

If flushing does not restore pressure, or if you are uncomfortable working with your water heater, call a plumber. A full tank drain and flush requires more steps and should be done by someone familiar with your heater's make and model.

When to call a plumber

Call a plumber if pressure remains low after you have cleaned aerators, checked the main shutoff, and tested the pressure regulator. You should also call if you find a leak in the main line, if your pressure regulator cannot be adjusted, or if flushing the water heater does not help.

A plumber can use specialized tools to check for blockages deeper in your plumbing, test your regulator under load, and diagnose problems you cannot see. The cost of a service call is usually $100 to $200, but catching a main line leak or failed regulator early can save thousands in water damage and wasted water.

Frequently Asked Questions

Why is my water pressure low only in the morning?

Low morning pressure often means your water heater is draining sediment into the main line overnight. Run hot water for a few minutes to flush it out, then check pressure again. If this happens regularly, your water heater needs flushing. If it happens only after the heater has been off for several hours, sediment is definitely the cause.

Can a clogged toilet fill valve cause low water pressure in the whole house?

No. A clogged toilet valve affects only that toilet's fill rate. If the whole house has low pressure, the problem is in the main line, pressure regulator, or main shutoff valve. If only one toilet fills slowly, the issue is the fill valve itself, which can be replaced for $15 to $30.

Does low water pressure mean I have a leak?

Not always. A leak will cause low pressure, but so will a clogged aerator, a closed shutoff valve, or a failed pressure regulator. Check your water meter while no water is running—if it is not moving, you do not have a leak. If it is moving, you do.

Should I replace my pressure regulator myself?

Replacement requires shutting off the main water line, unbolting the old regulator, and installing a new one with proper sealing. If you are comfortable with basic plumbing, you can do this, but if you are unsure, hire a plumber. An incorrectly installed regulator can fail suddenly and cause water damage.

What water pressure is normal for a house?

Normal household water pressure is between 40 and 60 psi. Anything below 40 psi will feel weak at the tap. Anything above 80 psi can damage pipes and appliances over time, which is why the pressure regulator exists. You can measure yours with a pressure gauge screwed onto any outdoor faucet.