How to Fix Low Water Pressure

Before changing anything, figure out how widespread the problem is, because it points straight to the cause. Open several fixtures around the house — kitchen, bathrooms, tub — and note whether the weak flow is at just one or everywhere, then check whether it's the hot side, the cold side, or both. One fixture means a local clog or valve; the whole house means a main valve, the pressure-reducing valve, or the supply; hot-only points at the water heater or its shutoff.

If only one faucet is weak, the cause is almost always a clogged aerator — the small screen at the tip of the spout that traps mineral scale and grit. Unscrew it by hand or with tape-wrapped pliers, and you'll usually find the mesh packed with white or rust-colored deposits. Soak the parts in white vinegar for an hour to dissolve the buildup, scrub the screen with an old toothbrush, and reassemble. Clean a weak showerhead the same way — unscrew and soak it, or tie a vinegar-filled bag over it overnight.

Look under the sink (or behind the toilet) for the small shutoff valves on the wall and make sure each is turned fully counterclockwise to open — a half-closed stop throttles just that fixture. Inspect the braided supply lines for sharp kinks, and if a faucet is weak on both hot and cold, suspect a clogged or failing cartridge inside it. These angle-stop valves can also scale up internally, so if one won't deliver full flow even wide open, it may need replacing.

For whole-house low pressure, go to the main shutoff where the water line enters the house — often in a basement, crawlspace, garage, or near the water heater. Older gate valves (the round wheel type) are easy to leave half-closed or to seize partway shut, so open it fully. If you can reach the meter valve on the street side, check that it's wide open too; utility crews sometimes leave it throttled after work.

Buy a water-pressure test gauge ($10-15) that screws onto a garden-hose thread. Attach it to an outdoor hose bib or the washing machine's cold-water connection, make sure no water is running anywhere, and open the tap fully. Healthy household pressure reads 40-60 psi, with 50-60 the sweet spot; below 40 is genuinely low, and above 80 is high enough to damage fixtures and needs a pressure-reducing valve to bring it down.

Many homes on city water have a pressure-reducing valve — a bell-shaped brass fitting on the main line just past the shutoff. If your gauge reads low everywhere, find the PRV's adjustment screw, loosen its lock nut, and turn the screw clockwise in small quarter-turns to raise pressure, re-checking the gauge after each. If turning the screw makes no difference at all, the PRV has failed internally — they wear out roughly every 7-12 years — and needs to be replaced.

If you have a whole-house sediment filter, a clogged cartridge is a very common and easily missed cause. Shut off the housing, unscrew the sump, and swap in a fresh pleated cartridge — they need changing every 3-6 months. If you have a water softener, set it to 'bypass' and see whether pressure returns; fouled resin or a unit stuck mid-regeneration can choke flow to the entire house.

If only the hot side is weak, the cause is on the hot plumbing. First confirm the shutoff valve on top of the water heater is fully open — a frequent culprit right after any heater service. Next, sediment in the tank bottom can restrict flow, so drain and flush the tank: shut the heater off, connect a hose to the drain valve, and run several gallons until it comes out clear. In older homes, corroded galvanized nipples at the heater connections narrow over time and may need swapping for brass or dielectric unions.