Where Low Water Pressure Comes From

Low water pressure usually starts at one of three points: the municipal supply line feeding your house, the main shutoff valve, or somewhere inside your plumbing. If your neighbors have normal pressure and you don't, the problem is on your property. If the whole block is low, call your water company — they may be doing work or have a main break.

The easiest culprit to check is the main shutoff valve, typically located where the water line enters your house, often in the basement or crawl space. This valve can partially close over time without you noticing. Turn it fully counterclockwise (lefty-loosey) and see if pressure improves within a few minutes. If it does, you have found your answer.

If the shutoff valve is already fully open, the problem is likely mineral buildup in aerators and screens, a failing pressure regulator, or a leak somewhere in your lines. Each has a different fix, and some require a plumber.

Key Takeaways

  • Check your main shutoff valve first — a partially closed valve is the quickest fix and costs nothing.
  • Mineral deposits in faucet aerators and showerheads are the second most common cause and can be cleaned by soaking in vinegar for a few hours.
  • A pressure regulator that has failed will need replacement by a plumber, usually costing $150 to $300 for the part and labor.
  • If pressure is low in only one room or fixture, the problem is local to that line and often fixable by cleaning or replacing the aerator.
  • Leaks inside your walls or under your foundation will require a plumber to locate and repair, and should not be ignored.

Clean Aerators and Showerheads

Mineral buildup inside faucet aerators and showerheads is the most common reason for low pressure in individual fixtures. An aerator is the small screen at the tip of your faucet. Over time, calcium and magnesium deposits clog the tiny holes.

Unscrew the aerator by hand or with a wrench if it is stuck. Soak it in white vinegar for two to four hours, then scrub the screen with an old toothbrush and rinse it thoroughly. Screw it back on and test the pressure. If pressure is still low, the aerator may be too clogged to clean — replace it with a new one from any hardware store for $3 to $8.

Do the same for showerheads. Unscrew the head, soak it in vinegar, scrub, and rinse. If you have low pressure throughout your whole house rather than in one fixture, cleaning aerators will not solve it — move to the next section.

Check for Leaks in Your Lines

A leak inside your walls, under your foundation, or in your yard will reduce pressure throughout the house. Look for soft spots in your yard, unusually green patches of grass, or water stains on basement walls or ceilings. Listen for running water sounds when all fixtures are off.

If you suspect a leak, turn off all water-using appliances and check your water meter. Write down the number, wait 30 minutes without using water, and check again. If the number has changed, you have a leak. A plumber can use a leak detection tool to find it without digging — this usually costs $100 to $200 and is worth it before you start tearing up your yard.

Do not ignore a leak. It wastes water, raises your bill, and can damage your foundation or create mold.

Replace or Adjust Your Pressure Regulator

A pressure regulator is a bell-shaped device usually located on the main water line where it enters your house, often near the shutoff valve. It keeps incoming pressure from the street from being too high and damaging your pipes. If it fails, pressure drops throughout the house.

A regulator can sometimes be adjusted. Look for a screw or bolt on top of the device. Turning it clockwise increases pressure; counterclockwise decreases it. Turn it a quarter turn at a time and wait a minute for the system to settle before testing. Do not force it — if it will not turn easily, stop.

If adjusting does not work or the regulator is stuck, it needs replacement. This is a job for a plumber because the regulator is under pressure and requires proper tools. Replacement typically costs $150 to $300 including labor. A new regulator usually lasts 10 to 15 years.

Install a Pressure Booster Pump

If your water company supplies consistently low pressure and you have ruled out problems on your property, a pressure booster pump can help. This device sits on your main water line and uses a motor to increase pressure throughout your house.

Booster pumps range from $300 to $800 for the unit, plus $200 to $500 for installation by a plumber. They require electricity and occasional maintenance. They are most useful if your municipal pressure is below 40 pounds per square inch (psi) — normal household pressure is 50 to 80 psi. Ask your water company what your incoming pressure is before you buy one.

A booster pump is a last resort after you have confirmed that the problem is not a closed valve, clogged aerators, a failed regulator, or a leak on your property.

When to Call a Plumber

Call a plumber if you have ruled out a closed shutoff valve and clogged aerators, or if you suspect a leak. A plumber can test your pressure with a gauge, locate leaks, and replace a regulator or install a booster pump. Most charge $100 to $150 for a service call, which usually includes a basic diagnosis.

Get a quote before work begins. If a plumber recommends replacing your entire water line or major replumbing, get a second opinion — these are expensive jobs and not always necessary.

Frequently Asked Questions

Why is my water pressure low in only one room?

A single-room problem is almost always a clogged aerator or showerhead, or a shutoff valve for that room that is partially closed. Check for a small valve under the sink or behind the toilet. If you find one, turn it fully counterclockwise. If that does not work, clean the aerator as described above.

What is normal water pressure?

Household water pressure is normally between 50 and 80 psi. You can buy a pressure gauge at a hardware store for $10 to $20 and screw it onto an outdoor faucet to check yours. If it reads below 40 psi, you have a real problem. If it reads 50 or higher, your pressure is fine and the issue is likely a clogged aerator.

Can I increase pressure by adjusting my water heater?

No. Your water heater does not control pressure — it only heats water that is already in your lines. Low pressure is a supply problem, not a heating problem. Adjusting your heater will not help.

How much does it cost to fix low water pressure?

Cleaning an aerator is free. Replacing one costs $3 to $8. A plumber's service call is $100 to $150. A pressure regulator replacement is $150 to $300 total. A booster pump is $500 to $1,300 installed. Start with the free and cheap fixes before paying for a service call.

Is low water pressure a sign of a serious problem?

Not always. A clogged aerator or a partially closed valve is harmless and straightforward to fix. A leak or a failed regulator should be addressed, but neither is an emergency unless water is actively pooling or spraying. A leak will waste water and money, so call a plumber within a few days if you suspect one.