Where low pressure starts: the main shutoff valve and meter

The first place to check is your main water shutoff valve, usually located where the water line enters your house—often in a basement, crawl space, or utility closet. This valve controls all water flow into your home. If someone partially closed it (which happens more often than you'd think during repairs), your pressure drops across every faucet and fixture.

Turn the valve handle counterclockwise to open it fully. If it's a ball valve, the handle should point in line with the pipe. If it's a gate valve (a wheel-shaped handle), turn it several full rotations. Once it's fully open, check your pressure at a kitchen sink—turn on the cold water and feel the force. If pressure jumps noticeably, you've found the problem.

Your water meter may also have a shutoff valve right next to it. This one should always be fully open as well. If you're renting, your landlord or property manager may need to adjust these valves.

Key Takeaways

  • Check your main shutoff valve first—a partially closed valve is the most common cause of low pressure throughout the whole house.
  • Sediment buildup in your water heater or supply lines reduces pressure and can be flushed out, though this requires draining tanks or calling a plumber.
  • A failing pressure regulator (if your home has one) can be replaced by a plumber for $150 to $300 in most areas.
  • Leaks in buried supply lines or inside walls are harder to spot but cause pressure loss and should be inspected by a professional if other fixes don't work.
  • If only one fixture has low pressure, the problem is local to that line, not your whole system.

Sediment in your water heater and supply lines

Over time, minerals and sediment settle inside your water heater and can clog the small openings where water enters and leaves. This buildup narrows the passages and reduces flow. If you notice low pressure only from hot water taps, your water heater is the culprit.

Flushing a water heater involves draining it completely and letting fresh water run through until it runs clear. This is a job many homeowners can do, but it requires turning off power or gas, connecting a hose to the drain valve at the bottom of the tank, and managing several gallons of hot water. If you're not comfortable with this, a plumber can do it in an hour or two for $150 to $300 depending on your region.

Sediment can also build up in the supply lines themselves, especially in older homes with galvanized steel pipes. If flushing the water heater doesn't help and you have low pressure everywhere, the lines themselves may need professional cleaning or replacement.

The pressure regulator: when it fails, pressure drops

Many homes have a pressure regulator installed where the main water line enters the house. This device keeps incoming water pressure at a safe level—usually between 40 and 80 pounds per square inch (psi). If the regulator fails, pressure can drop suddenly or become inconsistent.

You can check your current pressure with an inexpensive pressure gauge, available at any hardware store for $10 to $20. Screw it onto an outdoor faucet or a hose bib and turn the water on. A reading below 40 psi suggests a failing regulator. A reading above 80 psi means the regulator isn't doing its job of limiting pressure (which can damage fixtures, but that's a different problem).

If your regulator is failing, a plumber will need to replace it. The part itself costs $50 to $150, and labor typically runs $100 to $200, though this varies by location and how accessible the regulator is.

Leaks in supply lines you can't see

Water supply lines run through walls, under floors, and sometimes buried underground. A leak in any of these hidden sections reduces the pressure that reaches your fixtures. You might notice soft spots in drywall, damp crawl spaces, or unusually high water bills before you notice low pressure.

If you've ruled out the shutoff valve, water heater, and regulator, and pressure is still low everywhere, a hidden leak is possible. Look for signs: wet patches on walls or ceilings, mold, a musty smell, or a section of your yard that stays greener than the rest. If you find any of these, call a plumber. They can use specialized equipment to locate leaks without tearing into walls.

Repairing a hidden leak depends on where it is. A leak in an accessible supply line might cost $200 to $500 to fix. A buried line can be more expensive. But catching it early prevents water damage that costs far more.

When the problem is only one fixture

If only your kitchen sink, shower, or bathroom faucet has low pressure, the issue is local to that line, not your whole water system. Start by removing the aerator—the screen at the tip of the faucet. Unscrew it by hand or with a wrench, rinse it under running water, and screw it back on. Sediment often clogs aerators and is straightforward to clear.

If that doesn't help, the shutoff valve under that specific fixture may be partially closed. Look under the sink or behind the toilet and turn any valve handles counterclockwise to open them fully. If the valve is stuck or won't turn, don't force it—call a plumber to avoid breaking it.

For shower heads, you can soak the head in white vinegar overnight to dissolve mineral deposits, then rinse and reinstall it. If low pressure persists in one fixture after these steps, the supply line to that fixture may be clogged or damaged, and a plumber should inspect it.

When to call a plumber instead of troubleshooting

You can safely check and adjust shutoff valves and clean aerators yourself. Everything else—draining a water heater, testing a pressure regulator, locating hidden leaks, or replacing internal plumbing—should go to a licensed plumber. Mistakes with water lines can cause leaks, water damage, or contamination.

Call a plumber right away if you see signs of a leak (wet walls, mold, high water bills), if pressure dropped suddenly after no recent work on your system, or if adjusting the main shutoff valve didn't help. Most plumbers charge $100 to $200 for a service call, which includes diagnosis. Knowing what's wrong before they arrive saves time and money.

Frequently Asked Questions

What's normal water pressure for a house?

Most homes run between 40 and 80 psi. Anything below 40 psi feels weak at showers and faucets. Above 80 psi can damage fixtures and appliances over time. You can check yours with a pressure gauge on an outdoor faucet.

Can I increase pressure by adjusting my pressure regulator?

If your home has a regulator and pressure is below 40 psi, a plumber can adjust it upward—usually by turning a screw on top of the device. This is a quick fix if the regulator is working but set too low. However, if the regulator itself is broken, adjustment won't help and replacement is needed.

Why is my hot water pressure low but cold water is fine?

This almost always means sediment in your water heater. Flushing the heater usually solves it. If flushing doesn't work, the heater's internal dip tube may be failing, and the heater may need replacement.

How do I know if I have a water leak inside my walls?

Look for soft or discolored drywall, mold spots, a musty smell, or a section of floor that feels damp. You might also notice your water bill jumped without any change in usage. A plumber can use acoustic equipment to pinpoint leaks without opening walls.

Is low water pressure a safety issue?

Low pressure itself isn't dangerous, but it can indicate a leak or a problem with your water system. A hidden leak can cause water damage and mold. If pressure dropped suddenly, have it checked by a plumber to rule out damage.