Low water pressure: why, and what to do

One faucet or the whole house? That tells you where to look.

The answer in 2 lines. Start with one question: is the pressure low at one faucet, only on hot water, in the whole house, or on the whole street? The answer tells you where to look. A clogged faucet aerator takes ten minutes to clean; a half-closed main valve takes seconds; a drop across the neighborhood goes to your water utility. On a private well, the pressure tank and pump switch are the usual suspects.

The first 3 steps

Test several faucets, cold and then hot.
Ask a neighbor whether their pressure dropped too, and check your utility's website or social media for outages, main breaks or flushing.
Make sure the main shut-off valve is fully open: round handle turned counterclockwise all the way, or lever in line with the pipe.

Stop: danger

Pressure suddenly gone across the neighborhood: a main break or a loss of pressure can let contaminants into the pipes. Watch for a boil water notice from your utility or health department and follow it (what to do during a boil water advisory).
Low pressure plus water where it shouldn't be (wet ceiling, puddle, damp wall): you may have a leak. Close the main valve and see our guide on the first 10 minutes of a water leak.

Where to look, depending on what you see

One faucet or the shower: clogged aerator or showerhead, worn cartridge, kinked supply hose, or a fixture valve under the sink not fully open. Clean the aerator or showerhead; then check the cartridge.
Hot water only: the valve on the water heater's cold inlet not fully open, sediment in the tank, or a faulty mixing valve. Check the valves; for the heater itself, follow its manual or call a licensed plumber.
The whole house: main valve partly closed, a pressure-reducing valve (PRV) set too low or failing, a clogged whole-house filter or water softener, a leak, or old galvanized pipes narrowed by rust. Open the valve, check the filter, do the meter test.
The whole building or street: utility work, main break, hydrant flushing, or the building's booster pump. Call your water utility (number on your bill) or building management.

The simple fixes, in order

Aerator: unscrew the tip of the faucet (wrap it in a cloth if you use pliers), rinse the screen and soak it in white vinegar to dissolve mineral buildup, then put it back (Bob Vila: how to clean a faucet aerator).
Showerhead: same thing, soaked in vinegar or in a bag of vinegar tied around it.
Valves: open the main valve and the small valves under the sink fully, without forcing. After plumbing work, they're sometimes left half-closed.
Pressure-reducing valve (a bell-shaped brass valve where the main line enters, with an adjusting screw on top): if it's clogged or failing, pressure drops everywhere. Don't adjust it blind: an inexpensive water pressure gauge that screws onto an outdoor hose bib (sold at hardware stores; pick one reading 0 to 160 or 0 to 200 psi) tells you the actual pressure.
Leak: all faucets off and nobody using water, read the meter, wait one to two hours, read it again. If it moved, you have a leak, which can also lower pressure. See our guide on hidden leaks.

What not to do

Taking apart a pressure-reducing valve without shutting off the water.
Removing a pressure-reducing valve or cranking it up "for more flow": it protects your water heater, washer hoses and fixtures.
Taking the flow restrictor out of a showerhead: low-flow heads are designed to work at normal pressure, and the restrictor is part of the product's rating.

Too much pressure is a problem too

High pressure wears seals, makes faucets drip, bangs pipes (water hammer) and can trigger the water heater's relief valve.
The International Residential Code, used as a base by many states and cities, sets a minimum of 40 psi and, in its 2024 edition, requires a pressure-reducing valve when street pressure is over 80 psi (IRC 2024 summary; the 2027 edition was finalized in August 2026; PNNL Building America guide). Your state or city may use a different version or local amendments: your building department can confirm.

Good to know

Private well: pressure comes from your pump and pressure tank, not a utility. A pressure switch set too low, a waterlogged tank or a clogged sediment filter are common causes; a well contractor or licensed plumber handles the pump and tank.
Water-saving fixtures are not the problem: EPA WaterSense-labeled showerheads use no more than 2.0 gallons per minute and are tested to give a satisfying spray (EPA WaterSense showerheads).

Who to contact

Your water utility (number on the bill): low pressure on the street, outages, work, main breaks. Many publish their normal pressure range, like Wilsonville, Oregon or College Station, Texas. Ask yours what pressure to expect at your address.
Building management or HOA: low pressure in the whole building, booster pump, shared lines.
Your landlord, if you rent: report lasting low pressure in writing. Rules on what counts as adequate water supply depend on your state and city.

In Phoenix, Luis gets only a trickle at the kitchen faucet, while the bathroom is fine. He unscrews the aerator: the screen is caked with white mineral deposits. A night in white vinegar and a rinse later, the flow is back.

A made-up story, for illustration.

The numbers (latest published)

40 and 80 psi: the minimum and the level above which a pressure-reducing valve is required in the International Residential Code, 2024 edition. The 2027 edition was finalized in 2026; what applies to you is the edition your state or city has adopted, with its local amendments.
2.0 gallons per minute: the maximum flow of a WaterSense-labeled showerhead; the federal limit for showerheads is 2.5 gallons per minute.

Bobby

Sources, verification, confidence

Verified on November 1, 2026, for the United States. Confidence: high for the checks and safety advice; medium to high for the 40 and 80 psi thresholds, which come from the International Residential Code as summarized by PNNL and a code reference site (your state or city may differ); medium for the list of causes, which describes common cases, not a diagnosis.