Home / Plumbing / Low Water Pressure Causes
What causes low water pressure?
Quick answer
Start by deciding whether the pressure is low everywhere or only at one fixture, because those are two different problems. One weak faucet or shower usually means a clogged aerator, screen, or cartridge at that fixture. Low pressure at every tap, especially if it changed suddenly or has faded over years, points to a valve, a pressure regulator, aging pipes, a clogged whole-house filter, or a hidden leak.
Causes, most likely first
Clogged aerator or showerhead, one fixture only
Beginner. Mineral scale builds up in the small screen at a faucet tip and in showerhead holes, choking flow at that one outlet while the rest of the house stays normal. Unscrew the aerator by hand, rinse out grit, and soak it in vinegar overnight if scale is heavy. Clean showerheads the same way, in a bag tied around the head.
Main shutoff or meter valve not fully open
Beginner. After plumbing work, moving in, or a repair visit, a main valve sometimes gets left partly closed, and the whole house feels weak at once. Find your main shutoff and the valve at the water meter and confirm both are fully open. Gate valves in particular can look open while sitting half shut. Never force a stuck valve.
Clogged whole-house filter or softener
Beginner to intermediate. A sediment filter or softener protects the house, but a loaded filter cartridge quietly strangles pressure everywhere, often getting worse week by week. If pressure improves noticeably in filter bypass mode, you found it. Replace the cartridge with the correct model and note the date. Most homes need a change every three to six months.
Failing pressure regulator
Pro only. Many homes have a bell-shaped regulator near the main shutoff that holds street pressure down to a safe level. When it fails, pressure can drop across the whole house, swing up and down, or spike at night. A simple screw-on gauge at an outdoor spigot shows the pattern. Regulator work involves the main supply and belongs to a plumber.
Corroded galvanized or aging pipes
Pro only. Older galvanized steel pipes rust from the inside, narrowing year by year until flow fades, worst at upper floors and at the far end of the house. Brown water after a vacation and slow decline over years are the classic signs. No cleaning fixes a pipe that has rusted nearly shut. The lasting repair is partial or full repiping.
Hidden leak in the supply line
Pro only, urgent if confirmed. A leaking underground service line or a leak inside a wall steals pressure before water reaches your taps. Clues are a water meter that keeps spinning with everything off, a soggy yard patch, or the sound of running water in a quiet house. Check the meter test yourself, then call a plumber and your water utility promptly.
When to call a pro
- Pressure dropped suddenly across the whole house with no clear cause
- Water meter moves when every tap and appliance is off
- Rusty or discolored water along with falling pressure
- Wet spots in the yard, walls, or ceiling with no visible source
- Pressure is very high instead of low, above about 80 psi on a gauge
- The regulator, main valve, or any underground line is the suspect
What the repair typically costs
Directional national ranges for US homeowners. Your city and system age will move these.
| Repair | Typical cost |
|---|---|
| Aerators and cleaning supplies | $5 to $30 |
| Hose-bib pressure gauge for testing | $10 to $25 |
| Whole-house filter cartridge | $30 to $150 |
| Faucet cartridge replacement by a plumber | $200 to $450 |
| Pressure regulator replacement | $300 to $700 |
| Leak detection service | $150 to $400 |
| Whole-house repipe, size dependent | $4,000 to $15,000 |
Questions homeowners ask
What is normal home water pressure?
Most US homes run comfortably between 40 and 60 psi. Below about 40, showers and appliances feel weak. Above 80, pipes, hoses, and the water heater are under stress and code generally calls for a regulator.
Why is my pressure fine in the morning and weak in the evening?
That rhythm often tracks neighborhood demand, or a regulator and aging pipes that cannot keep up at peak times. A gauge reading morning and evening will show whether the supply or your own plumbing is changing.
Why is only the hot water pressure low?
If hot taps are weak but cold taps are strong, look at the water heater: a partly closed heater valve, sediment in the tank outlet, or a failing heater-side component is the usual cause, not the street supply.