Where Low Pressure Starts: Finding the Real Problem

Low water pressure usually comes from one of three places: a closed or partially closed valve, mineral buildup inside pipes or fixtures, or a problem with your water meter or main line. Before you spend money on equipment, you need to know which one you have, because the fix is different for each.

Start by checking whether the problem is everywhere in your house or only in one room. Turn on the kitchen sink, then a bathroom sink, then a shower. If pressure is low everywhere, the issue is likely in your main water line or the shut-off valve. If it's low in only one room, the problem is probably in that fixture or the supply line feeding it.

Key Takeaways

  • Check your main shut-off valve first—it may be partially closed, which is the easiest fix and costs nothing.
  • Mineral deposits inside aerators and showerheads can be cleaned by soaking them in white vinegar for several hours.
  • If pressure is low everywhere in your house, the problem is likely in your main line or meter, and you may need to contact your water company.
  • A pressure regulator that has failed will cause pressure to drop gradually over time and can be replaced by a plumber for $200 to $400.
  • Installing a water pressure booster pump costs $300 to $800 and is a last resort when all other causes have been ruled out.

Check Your Main Shut-Off Valve First

Your main shut-off valve controls water flow into your entire house. It is usually located near the water meter, in a basement, crawl space, or outside in a box in the ground. The valve may be a round knob or a lever handle. If someone has partially closed it—even slightly—your pressure will drop throughout the house.

Turn the valve all the way counterclockwise (if it's a knob) or fully horizontal (if it's a lever). Do this slowly and wait a few minutes, then test your pressure again. If pressure jumps back to normal, you have found the problem. If the valve is stuck or will not turn, do not force it—call a plumber, because forcing it can break the valve and leave you unable to shut off water in an emergency.

Clean Aerators and Showerheads of Mineral Buildup

Mineral deposits from hard water collect inside the small screens at the end of faucets and showerheads. Over time they block water flow and make pressure seem low in that one fixture. This is one of the easiest fixes you can do yourself in about 30 minutes.

Unscrew the aerator (the screen at the tip of the faucet) or the showerhead by turning it counterclockwise by hand. If it will not budge, wrap a cloth around it and use a wrench. Soak the part in white vinegar for at least two hours—overnight is better. Use an old toothbrush to scrub away the white or tan mineral crust. Rinse it under running water and screw it back on. If the aerator is too corroded to clean, replace it with a new one from any hardware store for $3 to $8.

Inspect Your Water Meter and Supply Line

If pressure is low everywhere and your shut-off valve is fully open, the problem may be in your water meter or the main supply line coming into your house. Your water meter has a shut-off valve on both sides of it. Check that both are fully open—one controls water coming in from the street, and the other controls water going into your house.

If both meter valves are open and pressure is still low, the problem is likely inside the meter itself or in the main line, which is buried underground. At this point, contact your water company. They can test pressure at the meter and tell you whether the problem is on their side of the line (the street) or on yours (inside your house). If it is on their side, they will fix it at no cost. If it is on your side, you will need a plumber.

Test and Replace Your Pressure Regulator

A pressure regulator is a bell-shaped device usually located on the main water line where it enters your house, just after the meter. It keeps water pressure from getting too high and damaging your pipes and fixtures. If the regulator fails, pressure will drop gradually over weeks or months.

To test it, attach a pressure gauge to an outdoor faucet or a laundry sink faucet. Turn on the faucet fully and read the gauge. Normal household pressure is 40 to 60 pounds per square inch (PSI). If your reading is below 40 PSI and your shut-off valve and meter valves are open, the regulator may have failed. A plumber can replace it for $200 to $400, depending on your location and the type of regulator.

Install a Water Pressure Booster Pump as a Last Resort

If your water company confirms that pressure at the meter is normal, your shut-off valve is open, your meter valves are open, and your pressure regulator is working, then your house may straightforward be receiving low pressure from the municipal system. This is common in older neighborhoods or areas at the edge of the water company's service zone.

A water pressure booster pump is a motorized device that increases pressure throughout your house. It costs $300 to $800 installed, plus $20 to $50 per year in electricity. A plumber will install it on your main water line, usually in the basement or crawl space. The pump turns on automatically when pressure drops below a set level and turns off when pressure reaches the target. Installation requires cutting into your main line, so this is not a do-it-yourself job.

Common Mistakes That Make Pressure Worse

Do not close the main shut-off valve all the way and then open it partway, thinking you can control pressure that way. The valve is designed to be either fully open or fully closed. Leaving it partially open can damage the valve and create a leak.

Do not assume that low pressure in one fixture means you need a whole-house solution. Clean the aerator first—it solves the problem 80 percent of the time and costs almost nothing. Do not call a plumber to install a booster pump until you have confirmed that pressure at the meter is actually low. Many homeowners pay for a pump they did not need because they skipped the pressure test.

Frequently Asked Questions

How do I know if my pressure regulator is broken?

Attach a pressure gauge to an outdoor faucet and turn it on fully. If the reading is below 40 PSI and your shut-off valve is fully open, the regulator may have failed. You can also watch for a gradual drop in pressure over several weeks—that is a sign the regulator is wearing out. A plumber can confirm this with a test.

Can I clean a showerhead without taking it off?

You can soak it in place by filling a plastic bag with white vinegar, tying it around the showerhead, and leaving it overnight. This works for light mineral buildup. For heavy buildup, you will get better results by unscrewing it and soaking it in a bowl of vinegar where you can scrub it with a brush.

What PSI should my water pressure be?

Normal household water pressure is 40 to 60 PSI. Below 40 PSI and you will notice weak flow from showers and faucets. Above 80 PSI and you risk damage to pipes, water heaters, and appliances. If your pressure is consistently above 80 PSI, a pressure regulator will protect your plumbing.

Will a booster pump work if my water company's pressure is very low?

Yes, a booster pump can increase pressure even if the incoming pressure is quite low. However, it cannot create water out of nothing—if your water company is experiencing a shortage or main break, a booster pump will not help. Call your water company first to rule out a system-wide problem.

How much does it cost to have a plumber test my water pressure?

A pressure test usually costs $75 to $150 and takes about 30 minutes. Many plumbers will waive the fee if you hire them to fix the problem. You can also buy a pressure gauge for $15 to $25 and test it yourself if you are comfortable with basic tools.