Where the problem starts: main valve, meter, and regulator

Low water pressure usually comes from one of three places: the main shut-off valve is partially closed, the water meter valve is not fully open, or a pressure regulator is set too low. Before you call a plumber, check these three things in order, because fixing any of them costs nothing.

The main shut-off valve is typically located where the water line enters your house — often in the basement, crawl space, or under the kitchen sink. It should be a lever handle (pointing along the pipe) or a round knob. Turn a lever handle so it points straight along the pipe direction. Turn a round knob counterclockwise until it stops. If the valve was partially closed, you may have just solved the problem.

Next, find your water meter, usually in a box in the ground near the street or in the basement. There is a valve on each side of the meter. The one on the street side is the city's responsibility. The one on your side should be fully open — lever handles point along the pipe, round knobs turn counterclockwise. Open it fully if it is not already.

Key Takeaways

  • Check your main shut-off valve and meter valve first — both are often partially closed by accident, and opening them costs nothing.
  • A pressure regulator, if you have one, can be adjusted upward with a wrench, but pressure above 80 psi can damage pipes and fixtures over time.
  • Mineral buildup in aerators and showerheads is the most common cause of low pressure in a single fixture, and cleaning takes 15 minutes.
  • If pressure is low everywhere and valves are open, the problem is likely at the water main or inside your pipes, and you will need a plumber to diagnose it.
  • Water pressure that fluctuates or drops when multiple fixtures run suggests a pipe diameter problem or a leak, both requiring professional inspection.

Adjusting the pressure regulator

If your valves are open and pressure is still low, look for a pressure regulator — a bell-shaped or cylindrical device on the main water line, usually within 3 feet of where water enters the house. Not all homes have one. If you see one, it has a screw or bolt on top under a plastic cap.

Turn the cap counterclockwise to remove it. Use an adjustable wrench to turn the screw or bolt clockwise — this increases pressure. Turn it a quarter turn, then turn the water on at a faucet and check the pressure. Repeat in small increments until pressure feels normal. Do not exceed 80 psi, because higher pressure damages pipes, water heaters, and fixtures. If you do not have a pressure gauge, you can buy one for $10 to $20 at any hardware store — screw it onto an outdoor faucet to read the current pressure.

If there is no regulator and you have confirmed both valves are fully open, the low pressure is coming from the water main or from inside your plumbing system, and you will need a plumber to measure pressure at the meter and diagnose the cause.

Cleaning aerators and showerheads when one fixture is slow

If pressure is low at only one faucet or showerhead, the problem is almost always mineral buildup inside the aerator — the screen at the faucet tip. Unscrew the aerator by hand or with a wrench, depending on how tight it is. Soak it in white vinegar for 30 minutes to dissolve mineral deposits, then scrub it with an old toothbrush and rinse it under running water.

Screw it back on and test the pressure. If pressure is still low, the clog may be deeper in the faucet body. Repeat the soak and scrub, or replace the aerator with a new one — they cost $2 to $5. For showerheads, the same method works: unscrew, soak in vinegar, scrub, and reinstall. If the showerhead has multiple spray settings, make sure you have not accidentally switched to a low-flow mode.

If cleaning the aerator does not help and the faucet is old, the problem may be inside the valve cartridge itself. Replacing a cartridge usually costs $20 to $50 in parts and can be done without calling a plumber if you follow the manufacturer's instructions, but if you are not comfortable taking apart plumbing, a plumber can do it in under an hour.

Diagnosing low pressure throughout the house

If pressure is low everywhere, start by checking whether it is low at the meter. Screw a pressure gauge onto an outdoor faucet that is closest to the meter. If the gauge reads below 40 psi, the problem is at the water main or in the line from the main to your house — call your water utility to report it. If the gauge reads above 60 psi, the problem is inside your home plumbing.

Low pressure inside the house usually means one of three things: mineral buildup in the main line (rare in newer homes, common in homes over 40 years old), a leak somewhere in the walls or underground, or pipes that are too small for the demand. If you suspect a leak, look for wet spots in the yard, unusually high water bills, or soft spots in the foundation. A plumber can use a pressure test to confirm a leak and locate it.

If there is no leak and pressure drops when multiple fixtures run at once, the pipes are likely undersized — common in older homes where plumbing was installed for fewer fixtures. This is expensive to fix (replacing main lines costs $3,000 to $10,000 depending on the house), but a plumber can confirm whether this is the cause by measuring pressure under load.

When pressure fluctuates or spikes

Pressure that bounces up and down, or spikes when you turn off a faucet, usually means a water hammer — a shock wave in the pipes when water flow stops suddenly. This is annoying but not dangerous unless it is severe. Install a water hammer arrestor, a small cylindrical device that screws onto the water line near the fixture causing the problem. They cost $15 to $30 and take 10 minutes to install if you are comfortable with a wrench.

Pressure that is very high and steady (above 100 psi) can damage pipes and fixtures over time. If your regulator is already adjusted to the lowest setting and pressure is still too high, you may have a faulty regulator that needs replacement. A new regulator costs $150 to $300 installed by a plumber.

When to call a plumber

Call a plumber if pressure at the meter is normal (60 to 80 psi) but low inside the house, or if you suspect a leak. Call if you have adjusted the regulator and pressure is still below 40 psi. Call if pressure fluctuates wildly or if you hear banging in the pipes that a water hammer arrestor does not fix. A plumber can run a pressure test, inspect for leaks with specialized equipment, and determine whether the problem is in the main line, a branch line, or a fixture.

Expect a service call to cost $100 to $200 for diagnosis. If the problem is a straightforward fix like a clogged aerator or a regulator adjustment, that is all you will pay. If the problem requires replacing a regulator, valve, or section of pipe, costs range from $300 to $1,500 depending on what needs to be done.

Frequently Asked Questions

What is normal water pressure for a house?

Normal pressure is between 40 and 80 psi. Most homes are set to 50 to 60 psi. Anything below 40 psi feels weak, and anything above 80 psi can damage pipes and appliances over time. You can measure your pressure with a gauge that screws onto an outdoor faucet.

Can low water pressure damage my pipes?

Low pressure itself does not damage pipes, but it can indicate a leak or a problem upstream. High pressure — above 80 psi — does damage pipes, water heaters, and fixtures by putting constant stress on joints and seals. If your pressure is consistently high, adjust the regulator or have it replaced.

Why is my water pressure low only in the morning?

Morning low pressure often means the water utility is doing maintenance on the main, or demand is very high in your neighborhood. It usually returns to normal within a few hours. If it happens every morning, call your water utility to ask whether they are doing work on your line.

Will increasing water pressure increase my water bill?

Slightly higher pressure will not significantly increase your bill, but very high pressure can cause small leaks at joints and fittings, which wastes water over time. Keep pressure between 50 and 80 psi to avoid this. If you notice your bill rising after adjusting the regulator, check for leaks.

Can I increase water pressure without a regulator?

If you do not have a regulator, you cannot increase pressure beyond what the water utility provides. You can only may support that your main valve and meter valve are fully open. If pressure is still low, the problem is at the water main, and you will need the utility or a plumber to diagnose it.