Start by finding where the pressure is low

Low water pressure everywhere in your house points to a problem with your main water line or the pressure regulator. Low pressure in only one room or at one fixture usually means a clog or mineral buildup in that specific line or faucet aerator. The location of the problem tells you what to fix.

Turn on a faucet in the kitchen, then one in a bathroom upstairs, then one in the basement if you have one. Write down which ones have weak flow and which ones are normal. If all of them are weak, the issue is upstream—either your municipal water supply is having problems, your main shutoff valve is partially closed, or your pressure regulator is failing. If only certain fixtures are weak, the problem is local to those lines.

Key Takeaways

  • Low pressure everywhere in your house usually means a closed shutoff valve, a failing pressure regulator, or a problem with your municipal supply.
  • Low pressure at one fixture often comes from a clogged aerator, mineral deposits in the line, or a closed isolation valve under the sink.
  • A pressure regulator typically sits where the main water line enters your house and can fail after 10 to 15 years.
  • Cleaning aerators and checking isolation valves are the first fixes to try because they cost nothing and take five minutes.
  • If pressure is low everywhere and your shutoff valve is fully open, call a plumber to test your regulator or check for a leak in the main line.

Check your main shutoff valve and isolation valves

Your main shutoff valve sits where the water line enters your house, usually in the basement, crawlspace, or under the kitchen sink. It should be fully open—the handle should point in the same direction as the pipe. If the handle is perpendicular to the pipe, it is partially or fully closed. Turn it to align with the pipe direction and test your pressure again.

Under each sink and behind each toilet there is also an isolation valve (sometimes called a stop valve). If someone turned one of these partway closed, it will cut pressure to just that fixture. Check under sinks and behind toilets in rooms where pressure is low. The valve handle should point in line with the pipe. If it is at an angle, turn it fully open.

Clean the aerator on your faucet

The aerator is the small screen at the tip of your faucet. Mineral deposits and sediment collect there and restrict flow. Unscrew the aerator by hand or with a wrench (wrap a cloth around it first so you do not scratch the finish). Rinse it under running water and use an old toothbrush to scrub away white or tan buildup.

If the aerator is heavily clogged, soak it in white vinegar for 30 minutes, then scrub again. Screw it back on and test the pressure. If pressure is still low at that faucet, the clog is deeper in the line—usually in the shutoff valve under the sink. In that case, you will need a plumber to replace the valve.

Inspect your pressure regulator

A pressure regulator is a bell-shaped or cylindrical device that sits on the main water line where it enters your house, usually right after the main shutoff valve. It keeps water pressure from the street at a safe level for your home's pipes and fixtures. Most regulators are set to 50 to 80 pounds per square inch (psi). If the regulator fails, pressure drops suddenly.

You can test your water pressure with a cheap pressure gauge from any hardware store. Screw it onto an outdoor faucet or a laundry sink faucet. If the reading is below 40 psi, your regulator may be failing. If it is above 100 psi, the regulator is not working at all. A regulator typically lasts 10 to 15 years. If yours is older and pressure is low everywhere, replacement is likely the answer. This is a job for a plumber—the regulator sits on the main line and requires soldering or professional connections.

Look for leaks in your main water line

A leak in the main line between the street and your house will reduce pressure throughout your home. Check your basement or crawlspace for wet spots, mold, or the sound of running water when all fixtures are off. If you see a wet patch under the floor or smell mold, there may be a leak below ground.

Another sign is a sudden spike in your water bill with no change in usage. If you suspect a leak, call a plumber. They can use a listening device or pressure test to confirm a leak and locate it. Main line leaks require excavation and are expensive, but they waste water and will only get worse.

Check whether your municipality has a supply problem

Sometimes low pressure is not your problem—it is the water company's. Call your local water utility and ask whether they are experiencing low pressure in your area. They can tell you in seconds. If they are, the pressure will return to normal when the problem is fixed on their end. There is nothing you can do until then.

If the utility confirms normal pressure on their side and your main shutoff valve is fully open, the problem is in your house. A plumber can test your regulator and check for leaks to pinpoint the cause.

When to call a plumber

Call a plumber if pressure is low everywhere in your house and you have already checked that your main shutoff valve is fully open and your water utility has normal pressure. A plumber will test your regulator with a pressure gauge, inspect the main line for leaks, and replace the regulator if it is failing. This usually costs between $300 and $500 for diagnosis and replacement, depending on your location and the type of regulator.

If pressure is low at only one fixture and cleaning the aerator did not help, a plumber can replace the isolation valve under that sink or toilet. This is a simpler job and costs less. Do not ignore low pressure for months—a failing regulator can eventually fail completely, or a leak can waste thousands of gallons and damage your foundation.

Frequently Asked Questions

Can low water pressure damage my pipes?

Low pressure itself does not damage pipes, but the cause might. A leak in the main line will eventually erode soil and weaken your foundation. A failing regulator that suddenly spikes pressure can crack pipes. If pressure drops suddenly or spikes, have a plumber investigate.

Why is my water pressure low only in the morning?

Morning low pressure is often caused by the water company flushing the main lines or by high demand in your neighborhood. It usually returns to normal within an hour. If it happens every morning and lasts all day, the problem is in your house—check your shutoff valve and regulator.

Does a water softener affect water pressure?

A water softener can slightly reduce pressure if it is undersized or clogged with sediment. If you have a softener and pressure dropped recently, ask a plumber to check whether the softener needs cleaning or replacement of its filter cartridge.

What is normal water pressure for a house?

Normal household water pressure is 40 to 80 psi. Anything below 40 psi feels weak. Above 80 psi can strain pipes and fixtures over time. A pressure gauge from a hardware store lets you measure your own pressure in minutes.

Can I increase water pressure myself?

You can adjust a pressure regulator if you know how, but it requires a wrench and care not to over-tighten. Most homeowners should not attempt this—if you turn it the wrong way, you can damage it or create a leak. A plumber can adjust it safely in minutes.