Where the problem starts: main shutoff valve and pressure regulator
Low water pressure in your house usually comes from one of two places: the main shutoff valve (the one that controls water entering your home from the street) is partially closed, or your pressure regulator is set too low. The main shutoff is the simplest fix. It sits where the water line enters your house, often in a basement, crawl space, or utility closet near the foundation. Look for a valve with a handle shaped like a wheel or a lever.
If the handle is a wheel, turn it counterclockwise (lefty-loosey) to open it fully. If it is a lever, it should point in the same direction as the pipe when fully open. Turn it slowly—do not force it. You should feel resistance ease as you go. If the valve is already fully open, the problem is likely your pressure regulator, a bell-shaped or cylindrical device mounted on the main water line just after the shutoff valve.
A pressure regulator keeps water pressure from getting too high and damaging your pipes and fixtures. If it is set too low, you get weak flow everywhere. Most regulators have a screw on top or a bolt on the side. Before you adjust it, buy an inexpensive water pressure gauge (under $15 at any hardware store) and screw it onto an outdoor faucet or a laundry sink faucet to measure your current pressure.
Key Takeaways
- Check that your main shutoff valve is fully open by turning the wheel counterclockwise or pointing the lever in line with the pipe.
- Measure your current water pressure with a gauge on an outdoor or utility faucet before adjusting anything—normal household pressure is 40 to 60 pounds per square inch.
- Adjust your pressure regulator by turning the adjustment screw clockwise to increase pressure, but do not exceed 80 pounds per square inch.
- If pressure is low only in one room or fixture, the problem is likely a clogged aerator or a closed shutoff valve under that sink, not your main regulator.
- Sediment buildup in your pipes or a failing pressure regulator may require a plumber if straightforward adjustments do not work.
Measuring water pressure and adjusting the regulator
Normal household water pressure ranges from 40 to 60 pounds per square inch (psi). Anything below 40 psi feels weak; above 80 psi can damage washers, water heaters, and pipes over time. Screw your pressure gauge onto the faucet and turn it on fully. Read the dial and write down the number.
If your pressure is below 40 psi and your main shutoff is fully open, locate the adjustment screw on your pressure regulator. It is usually a bolt or nut on top of the device, sometimes covered by a plastic cap. Using an adjustable wrench or the correct socket size, turn the screw clockwise (righty-tighty) one-quarter turn at a time. After each quarter turn, wait 30 seconds and check your pressure gauge again. Stop when you reach 50 to 60 psi. Do not exceed 80 psi.
If the screw will not turn or turns freely without changing pressure, the regulator may be broken and need replacement. If you are not comfortable working with wrenches or your regulator is stuck, this is the point to call a plumber.
Checking for closed shutoff valves under individual sinks
If pressure is low in only one bathroom or kitchen sink, the problem is almost never your main regulator. Instead, look under that sink for a small shutoff valve—a knob or lever on the water line coming in. This valve may have been partially closed during a repair and forgotten. Turn it fully open the same way you would the main shutoff: wheel counterclockwise, or lever pointing along the pipe.
If that valve is already open and pressure is still low in just that one sink, the aerator (the screen at the faucet tip) is probably clogged with sediment. Unscrew the aerator by hand or with a wrench, rinse it under running water, and screw it back on. If pressure improves, you are done. If not, the supply line to that fixture may be blocked, and a plumber will need to check it.
Cleaning aerators and strainers
Sediment and mineral buildup inside aerators and strainers can reduce flow without affecting pressure elsewhere in the house. An aerator is the removable screen at the tip of your faucet. Hold the faucet body steady with one hand and unscrew the aerator counterclockwise with the other. If it is stuck, wrap a cloth around it for grip or use an adjustable wrench.
Once removed, rinse it under hot water and use an old toothbrush to scrub away any white or brown deposits. If deposits are heavy, soak the aerator in white vinegar for 30 minutes, then brush again. Screw it back on hand-tight—do not over-tighten. Turn on the faucet and check the flow. If pressure is still low, the problem is inside the faucet body or the supply line, not the aerator.
When sediment is blocking your whole system
If pressure is low everywhere in your house and your main shutoff is open and your regulator is set correctly, sediment may have built up inside your main water line or in the meter. This is more common in older homes or areas with hard water. You cannot fix this yourself, but you can narrow down the problem before calling a plumber.
Turn on an outdoor faucet (a hose bib) if you have one. If pressure is normal there, the blockage is in your indoor pipes. If pressure is low there too, the blockage is in the main line or meter, and your water company or a plumber will need to clear it. If you have a whole-house water filter, check whether it is clogged—a filter that needs replacement will reduce pressure throughout the house. Replace it according to the manufacturer's instructions, usually every 6 to 12 months depending on water quality.
When to call a plumber instead of adjusting yourself
Call a plumber if your main shutoff valve will not turn or if turning it causes water to spray or leak. Do not force a stuck valve—you may break it and lose the ability to shut off water in an emergency. Also call a plumber if your pressure regulator screw will not turn, turns but does not change pressure, or if adjusting it causes leaks at the connection.
If you have adjusted the regulator correctly and pressure is still below 40 psi everywhere, or if pressure is low in only one fixture and cleaning the aerator did not help, a plumber can check for leaks, blockages, or a failing regulator that needs replacement. A service call usually costs $100 to $200 and takes 30 minutes to an hour for diagnosis.
Frequently Asked Questions
What is normal water pressure for a house?
Normal household water pressure is 40 to 60 pounds per square inch. Below 40 psi feels weak and slow. Above 80 psi can damage appliances and pipes. You can measure your pressure with an inexpensive gauge screwed onto any faucet.
Can low water pressure damage my pipes or appliances?
Low pressure itself does not damage pipes. High pressure does—above 80 psi puts stress on connections and can shorten the life of water heaters and washing machines. Low pressure is annoying but safe.
Why is my water pressure low in only one room?
Check the shutoff valve under that sink or behind that fixture—it may be partially closed. If it is fully open, the aerator at the faucet tip is probably clogged. Unscrew and rinse it. If neither fixes it, the supply line to that room may be blocked.
How often should I replace my whole-house water filter?
Most whole-house filters need replacement every 6 to 12 months, depending on how much sediment is in your water. Check your filter's instructions. A clogged filter will reduce pressure throughout the house.
Is it safe to adjust my pressure regulator myself?
Yes, if you use a wrench and turn the adjustment screw slowly, one-quarter turn at a time. Do not exceed 80 psi. If the screw will not turn or leaks appear, stop and call a plumber.