Where Low Water Pressure Comes From

Low water pressure usually starts at one of three places: the municipal supply line feeding your house, the main shutoff valve, or somewhere inside your plumbing. If your neighbors have normal pressure and you don't, the problem is on your property. If the whole block is low, call your water company—they may be flushing lines or dealing with a main break.

The most common culprit inside your home is a pressure regulator—a bell-shaped device on the water line where it enters your house, usually near the main shutoff valve. It's designed to protect your pipes from damage by capping pressure at a safe level. If it's set too low or has failed, your pressure drops. The second common cause is mineral buildup inside the aerators (the screens on faucet tips) or in the shutoff valve itself, which narrows the opening water has to flow through.

Key Takeaways

  • Check whether low pressure is everywhere in your house or only at certain fixtures—this tells you whether the problem is in the main line or a single faucet.
  • The pressure regulator, a bell-shaped device near your main shutoff valve, can be adjusted upward if it's set too low, but you need a pressure gauge to do it safely.
  • Mineral deposits in aerators and shutoff valves can be cleaned or replaced without tools beyond a wrench and a bucket.
  • If pressure is low only at hot water taps, the problem is usually in your water heater or the line feeding it, not the main supply.
  • A plumber should diagnose the problem if you cannot locate the regulator, if adjusting it doesn't help, or if pressure drops suddenly after being normal.

Adjusting the Pressure Regulator

If you have a pressure regulator (most homes built after 1980 do), you can adjust it yourself if you have a water pressure gauge—a straightforward dial tool that screws onto an outdoor faucet or a washing machine outlet. Buy one at any hardware store for $10 to $20. First, screw the gauge onto an outdoor spigot and turn the water on. Write down the reading. Normal household pressure is 40 to 80 pounds per square inch (psi). If you're below 40 psi, the regulator may be your answer.

Locate the regulator—it's a brass or plastic bell-shaped fitting on the main water line, usually within 3 feet of where the line enters your house. On top, you'll see a hexagonal nut or an adjustment screw. If it's a screw, turn it clockwise (to the right) a quarter turn, then recheck the gauge at the outdoor faucet. Increase pressure in small steps—a quarter turn at a time—until you reach 50 to 60 psi. Do not exceed 80 psi; high pressure damages pipes and appliances. If the regulator has no adjustment screw, or if adjusting it makes no difference, it has failed and needs replacement by a plumber.

Cleaning Aerators and Screens

Mineral deposits clog the tiny screens on faucet tips and inside shutoff valves, restricting water flow. This is especially common in areas with hard water. Start with the aerator—the removable piece at the tip of your faucet. Unscrew it by hand or with a wrench wrapped in a cloth (to avoid scratching). Rinse it under running water and use an old toothbrush to scrub away white or brown deposits.

If deposits are heavy, soak the aerator in white vinegar for 30 minutes, then scrub again. Rinse thoroughly and screw it back on. If pressure improves at that faucet, you've found the problem. If low pressure is everywhere in the house, the deposits may be in the main shutoff valve. This is more involved—you'll need to turn off water at the meter, unscrew the valve, and clean the internal screen the same way. If you're not comfortable doing this, a plumber can do it in under an hour.

Checking for Leaks and Blockages

A slow leak inside your walls or under your foundation reduces pressure throughout the house. Listen for running water when all taps are off and no appliances are running. Check your water meter—if the dial is moving when nothing is using water, you have a leak. Mark the meter reading, wait an hour without using water, and check again. If it has changed, call a plumber to locate the leak.

Blockages in the main line are rare but possible, especially in older homes with galvanized steel pipes that rust from the inside. If pressure dropped suddenly and you've ruled out the regulator and aerators, a plumber can run a camera through the line to check. This is not a DIY fix, but knowing what to expect helps you decide whether the cost is worth it.

Separating Hot and Cold Water Problems

If low pressure happens only when you turn on the hot water tap, the problem is not your main supply—it's your water heater or the line feeding it. Check the shutoff valve on the cold water line going into the heater; it may be partially closed. Turn it fully open (the handle should be parallel to the pipe). If that doesn't help, the heater's internal dip tube may have failed, or sediment may have built up inside the tank. Both require a plumber.

If cold water pressure is normal but hot water is weak everywhere, and the shutoff valve is fully open, the heater itself is the issue. Do not try to repair a water heater yourself—they operate under pressure and temperature that can cause injury. Call a licensed plumber or the heater manufacturer's service line.

When to Call a Plumber

You can handle aerator cleaning and regulator adjustment on your own. Call a plumber if the regulator has no adjustment screw, if adjusting it doesn't raise pressure, if you cannot locate the regulator, or if pressure dropped suddenly after being normal. A plumber can also run a pressure test to confirm the regulator is working, check for leaks you can't see, and diagnose blockages in the main line.

If you rent, contact your landlord or property manager before touching anything—they are responsible for water pressure and may have already scheduled a repair. Adjusting a regulator without permission could void a warranty or violate your lease.

Frequently Asked Questions

Can I increase water pressure by opening the main shutoff valve more?

The main shutoff valve is either fully open or fully closed—there is no in-between position that increases pressure. If the handle is perpendicular to the pipe, it's closed. Turn it parallel to the pipe to open it fully. If it's already open and pressure is still low, the problem is downstream, not at the shutoff.

What if I adjust the regulator and pressure goes too high?

Turn the adjustment screw counterclockwise (to the left) a quarter turn and recheck with the gauge. High pressure damages pipes, water heaters, and washing machines, so it's worth taking time to get it right. Aim for 50 to 60 psi.

Does low water pressure mean I have a leak?

Not always. Leaks are one cause, but a faulty regulator, clogged aerators, or a failing water heater are more common. Check your meter as described above—if it's not moving when nothing is running, you probably don't have a leak.

Will cleaning the aerator fix low pressure everywhere in my house?

Only if the problem is in that one faucet. If pressure is low at multiple taps, the issue is in the main line, the regulator, or the shutoff valve. Start by checking the regulator and the main shutoff valve.

How much does it cost to have a plumber fix low water pressure?

A service call to diagnose the problem typically costs $100 to $200. If the fix is a regulator adjustment or aerator cleaning, that's usually included. Replacing a regulator or water heater costs more and depends on your location and the equipment.