When the showerhead sputters or the washing machine takes forever to fill, low water pressure is more than an annoyance—it can disrupt daily routines and even trigger appliance error codes. Before picking up the phone to call a plumber, there are several checks and adjustments a homeowner can safely perform. Most causes of weak flow are straightforward, such as a partially closed valve, a clogged screen, or a leak somewhere in the supply line.
The first step is to measure the actual pressure. A basic water pressure gauge, available at most hardware stores, screws onto an outdoor hose spigot. With the water turned on, the gauge reads the pressure in pounds per square inch (psi). A reading between 40 and 60 psi is considered normal; anything below 40 psi confirms a problem. To measure flow rate, place a few containers of known capacity—like 5-gallon buckets—under the hose, turn it on fully, and time how long it takes to fill them. The number of gallons collected in one minute gives the flow in gallons per minute (GPM). Before running this test, ensure no other faucets or appliances are drawing water.
Start With the Valves
A common culprit is a main water valve that isn't fully open. Locate the main shutoff valve, usually near the water meter or where the line enters the house, and confirm it is turned all the way. Some homes also have a valve at the street, though access may be restricted. If the low pressure is isolated to one fixture, check the shutoff valves on that specific supply line.
Inspect for Leaks and Clogs
Even a small leak in the supply line can cause a noticeable drop in pressure. While less frequent, a clog in the line can also restrict flow. If the plumbing is relatively new, a clog is unlikely, but older pipes may accumulate sediment. For a single fixture, the problem is often a blocked aerator or screen. Remove and clean these parts to clear any debris.
Adjust the Pressure Reduction Valve
If pressure remains low after checking valves and cleaning screens, the next step is the pressure reduction valve (PRV). This device, typically located where the main line enters the house, limits the incoming pressure from the utility to a safe level. Turning the adjustment bolt or knob clockwise usually increases pressure, but only if the valve isn't already fully open. If adjusting the PRV produces no change, the valve may be faulty and require replacement—a job for a professional. Because the PRV protects pipes and appliances from excessive pressure, adjustments should be made carefully.
When to Consider a Booster Pump
If all else fails, a plumber can install a water pressure booster. This device uses a pump and a pressure tank to raise the pressure throughout the home. It's a more involved solution, but it can resolve persistent low pressure that isn't caused by leaks, clogs, or valve issues.
Knowing when to call a plumber is just as important as knowing when to DIY. If no obvious cause is found, or if the pressure suddenly drops without explanation, professional help is warranted. A plumber can identify underlying issues such as corroded pipes or a failing PRV and restore proper flow.
By methodically checking valves, cleaning aerators, and testing the PRV, most homeowners can resolve low water pressure without a service call—saving time and money while keeping the system running smoothly.
