Where Low Water Pressure Usually Comes From

Low water pressure falls into two categories: it either affects your whole house or just one fixture. If every tap, shower, and toilet runs weak, the problem is usually at the meter, in the main line coming into your house, or at your water supplier. If only one sink or shower is weak, the blockage is downstream—in that fixture's supply line or inside the fixture itself.

The most common causes are mineral buildup inside aerators and showerheads, a closed or partially closed shut-off valve, a leak somewhere in your line that you cannot see, or sediment in your pipes after water main work in your neighborhood. Less often, your water supplier has reduced pressure on your street, or your home's pressure regulator has failed.

Key Takeaways

  • Check whether low pressure affects one fixture or your whole house—this tells you whether to look at the fixture itself or your main water line.
  • The fastest fix is usually cleaning the aerator on a single faucet or the screen on a showerhead, which takes five minutes and costs nothing.
  • If your whole house has low pressure, check that the main shut-off valve under your sink or in your basement is fully open.
  • A leak in your main line or a failed pressure regulator requires a plumber, but you can narrow down the problem before you call.
  • If pressure dropped suddenly after water main work on your street, call your water supplier first—they may need to flush the line.

Cleaning Aerators and Showerhead Screens

An aerator is the small screen at the tip of a faucet. A showerhead has a similar screen. Mineral deposits from hard water build up on these screens and restrict flow. This is the easiest and cheapest fix to try first.

For a faucet aerator: unscrew the aerator by hand (it twists counterclockwise). If it is stuck, wrap a cloth around it and use pliers. Soak it in white vinegar for 30 minutes to dissolve mineral buildup. Use an old toothbrush to scrub the screen, rinse it, and screw it back on. For a showerhead: unscrew the entire head, soak it in vinegar the same way, scrub the holes, and reinstall it. If the screen is badly corroded, you can buy a replacement aerator or showerhead for $5 to $15 at any hardware store.

Checking Your Main Shut-Off Valve

Every house has a main shut-off valve where the water line enters from the street. It is usually under the kitchen sink, in the basement near the foundation, or in a box in your front yard. If this valve is not fully open, it will reduce pressure throughout your house.

The valve has a handle. If the handle is a lever, it should point in the same direction as the pipe (parallel to it). If it points across the pipe (perpendicular), the valve is closed or partially closed. Turn it so it lines up with the pipe. If the handle is a round knob, turn it counterclockwise until it stops. Do not force it. If the valve is stuck or will not turn, do not damage it—call a plumber. Once you open it fully, check whether pressure improves. It may take a few minutes for pressure to build.

Finding Out If You Have a Leak

A leak in your main water line—the pipe running from the street to your house—will lower pressure throughout your home. You cannot always see this leak because it may be underground or inside a wall.

To check for a leak, turn off all water-using appliances and fixtures in your house. Then look at your water meter. If the meter is still running or the numbers are still changing, you have a leak. Write down the meter reading, wait 30 minutes without using any water, and check again. If the reading has changed, water is leaking somewhere. Call a plumber—they have equipment to find the leak without tearing up your yard. If the meter does not move, your pressure problem is not a leak.

Testing Individual Fixtures

If only one faucet or shower has low pressure, the problem is in that fixture's supply line or inside the fixture itself. Start by checking the shut-off valve under that sink or behind that toilet. It should be fully open (handle parallel to the pipe, or knob turned counterclockwise). If it is partially closed, open it.

Next, disconnect the supply line at the fixture and turn the water on briefly into a bucket. If water flows strongly, the problem is in the fixture itself—the aerator, cartridge, or internal screen is blocked. Clean or replace the aerator as described above. If water does not flow strongly even from the disconnected line, the supply line itself is blocked or kinked. Check that the line is not bent or pinched. If it looks fine, the blockage is inside the line and you need a plumber.

When to Call a Plumber

Call a plumber if you have confirmed a leak in your main line, if your pressure regulator has failed, or if a supply line is blocked inside a wall. You should also call if your main shut-off valve is stuck or damaged, or if pressure is low throughout your house and cleaning aerators and checking the shut-off valve did not help.

Before you call, tell the plumber whether the problem affects one fixture or your whole house, whether it started suddenly or gradually, and whether you have recently had water main work done on your street. This information helps them diagnose the problem faster. A plumber can also test your water pressure with a gauge—normal household pressure is 40 to 80 pounds per square inch (PSI). If your pressure is below 40 PSI and you have no leak, your pressure regulator may need adjustment or replacement.

What to Do After Water Main Work on Your Street

If your water pressure dropped right after your water supplier did work on the main line in your neighborhood, call your water supplier's customer service line before you call a plumber. Water main work often stirs up sediment in the pipes. The supplier may need to flush the line to clear it, which they can do from the street.

Ask them to flush the line serving your block. This usually takes a few hours and is free. If pressure does not improve after flushing, then you can call a plumber to check your home's internal lines and pressure regulator.

Frequently Asked Questions

Can low water pressure damage my pipes?

Low pressure itself does not damage pipes, but it can be a sign that something else is wrong—a leak, blockage, or failed regulator. A leak will damage your home over time if left unfixed. If pressure is very low (below 20 PSI), some appliances like dishwashers and washing machines may not work properly, but they will not break.

Why is my water pressure low only in the morning?

Morning pressure dips are common in neighborhoods where many people use water at the same time. Your water supplier may also do maintenance work early in the morning, which temporarily reduces pressure. If pressure returns to normal by mid-morning, this is normal and not a problem in your home. If it stays low all day, follow the steps above.

Does a water softener affect pressure?

A water softener can slightly reduce pressure if it is undersized for your home's flow rate or if the resin bed is clogged. If you recently installed a softener and pressure dropped, check that it is sized correctly for your household. If pressure was already low before the softener, the softener is not the cause.

What does a pressure regulator do?

A pressure regulator is a valve that reduces water pressure from the street (which can be 100+ PSI) down to a safe level for your home (40 to 80 PSI). If it fails, pressure either drops too low or spikes too high. A plumber can test it with a gauge and replace it if needed, usually for $200 to $400.