Where low water pressure comes from, and what you can fix yourself
Low water pressure usually starts at one of three points: the main shutoff valve, the pressure regulator, or mineral buildup inside pipes and fixtures. The main shutoff valve and pressure regulator are both things you can adjust yourself in about ten minutes. Mineral deposits take longer to clear but do not require a plumber. If pressure is low everywhere in the house at the same time, start with the shutoff valve and regulator. If it is low in only one room or at one fixture, the problem is almost certainly mineral buildup in that line.
Before you do anything, measure your current pressure so you know whether the problem is real or just feels that way. A water pressure gauge costs $8 to $15 at any hardware store and screws onto an outdoor faucet or a washing machine connection. Normal household pressure is 40 to 60 pounds per square inch (psi). Anything below 40 psi will feel weak; anything above 80 psi can damage pipes and appliances over time.
Key Takeaways
- Check your water pressure with a $10 gauge before assuming there is a problem—normal pressure is 40 to 60 psi, and anything below 40 psi is worth fixing.
- The main shutoff valve is often partially closed by accident; opening it fully takes seconds and solves low pressure in most homes.
- If pressure is still low after the shutoff valve is fully open, adjust the pressure regulator (a bell-shaped device on the main water line) by turning its adjustment screw clockwise.
- Mineral buildup in a single fixture or line can be cleared by soaking the aerator or showerhead in vinegar, or by flushing the line with a plumber's snake.
- If pressure stays below 40 psi after these steps, or if it drops suddenly, call a plumber to check for leaks or problems with the municipal supply.
Check and open the main shutoff valve
The main shutoff valve is the first place water enters your house from the street. It is usually located in the basement, crawlspace, or utility room near the foundation wall, or sometimes in a box buried in the yard. The valve looks like a handle or a knob attached to a pipe about the size of a quarter or half-dollar.
If the handle is a lever (shaped like a wrench), it should point in the same direction as the pipe—parallel to it. If it points across the pipe (perpendicular), the valve is partially or fully closed. Turn it so it lines up with the pipe. If the valve is a round knob, turn it counterclockwise (lefty-loosey) until it stops. Do not force it; if it is stuck, stop and call a plumber rather than risk breaking it.
After opening the valve fully, turn on a faucet and wait 30 seconds for air to clear the line, then check your pressure again with the gauge. This single step fixes low pressure in roughly half of all homes.
Adjust the pressure regulator if the shutoff valve is already open
If the main shutoff valve was already open or opening it did not raise pressure, the next step is the pressure regulator. This is a bell-shaped or cylindrical device usually found on the main water line just after the shutoff valve. It has a screw or bolt sticking out of the top, sometimes with a plastic cap covering it.
The regulator controls how hard water pushes through your pipes. If it is set too low, pressure will be weak everywhere. To raise it, turn the adjustment screw clockwise (righty-tighty) a quarter turn at a time. After each quarter turn, wait 30 seconds and check your pressure with the gauge. Stop when you reach 50 to 60 psi. Do not exceed 80 psi, because high pressure damages water heaters, washing machines, and pipes.
If the regulator has no adjustment screw, or if turning it does not change pressure, the regulator itself may be faulty and will need to be replaced. This is a job for a plumber, though the part itself costs $30 to $100.
Clear mineral buildup in aerators and showerheads
If pressure is low in only one faucet or showerhead, mineral deposits are almost certainly the cause. Calcium and magnesium in hard water build up inside the aerator (the screen at the tip of the faucet) or inside the showerhead, blocking flow.
Unscrew the aerator or showerhead by hand or with a wrench, then soak it in white vinegar for 4 to 8 hours. The vinegar dissolves mineral deposits. After soaking, scrub the inside with an old toothbrush, rinse it thoroughly, and screw it back on. If the aerator or showerhead is very clogged, you may need to soak it overnight or replace it entirely (they cost $5 to $20).
For a faucet that is low-pressure but has no removable aerator, or for a shower valve that is clogged inside the wall, you will need a plumber to disassemble and clean the internal parts.
Flush mineral buildup from supply lines
If an entire bathroom or kitchen has low pressure, mineral buildup may be inside the supply line itself rather than just at the fixture. You can sometimes clear this by opening the shutoff valve under that sink or behind that toilet all the way, then closing it and opening it again rapidly several times. This surge of pressure can dislodge loose deposits.
If that does not work, a plumber can use a tool called a plumbing snake or a pressurized water jet to flush the line from inside. This costs $150 to $300 depending on how long the line is and how stubborn the buildup is. It is worth doing if the line is old (20+ years) and you want to avoid replacing it.
In very old homes with galvanized steel pipes, mineral buildup is often so severe that flushing does not help for long. In those cases, replacing the affected section of pipe is usually the only permanent fix. A plumber can assess whether your pipes are worth flushing or whether replacement makes more sense.
When to call a plumber instead of troubleshooting
Call a plumber right away if pressure drops suddenly (it was fine yesterday, now it is not), because this usually means a leak somewhere in your main line or in the city supply. A sudden drop is not something you can fix yourself, and the longer you wait, the more water you lose and the more damage occurs.
Also call a plumber if pressure stays below 40 psi after you have opened the shutoff valve fully and adjusted the regulator. This suggests a problem with the municipal supply, a leak you cannot see, or a regulator that is broken and needs replacement.
If you are not comfortable opening the shutoff valve or adjusting the regulator, or if you are not sure which device is which, a plumber can do both in a service call that usually costs $100 to $200. It is a small job and worth paying for if it saves you the stress of guessing.
Frequently Asked Questions
Can high water pressure damage my pipes?
Yes. Pressure above 80 psi puts constant stress on pipes, joints, and appliances. Over months or years, this causes leaks, burst pipes, and premature failure of water heaters and washing machines. If your gauge reads above 80 psi, lower the regulator adjustment screw counterclockwise until pressure drops to 60 to 70 psi.
Why is my water pressure low in only one room?
Mineral buildup in that room's supply line or in a single fixture is the most common cause. Start by soaking the aerator or showerhead in vinegar. If that does not help, the clog is deeper in the line and a plumber will need to flush or replace that section of pipe.
Should I replace my pressure regulator if it is old?
Regulators typically last 10 to 15 years. If yours is older than that and pressure is low, replacement is often cheaper than repeated repairs. A plumber can test it to confirm it is faulty before you commit to replacing it.
What if my house does not have a pressure regulator?
Older homes sometimes lack a regulator. If your pressure is consistently above 80 psi, a plumber should install one to protect your pipes and appliances. If pressure is normal (40 to 60 psi), you do not need one.
Can I raise water pressure by adjusting something at the meter?
No. The meter is owned and sealed by the water company, and adjusting it is illegal. All pressure control happens at the regulator inside your home. If you suspect the meter is faulty, contact your water company to have them test it.