Low Water Pressure in the House: One Faucet, the Hot Side, or Everywhere

Where the weak flow shows up tells you most of what you need to know. One faucet or showerhead points to that fixture. Weak hot water with normal cold points to the water heater. Weak flow everywhere, outdoor spigots included, points to the main valve, a filter or softener, a pressure-reducing valve, a leak, old pipes, a well, or the utility. Portland Water Bureau says pressure problems are most likely in the home's plumbing, though main breaks can lower pressure for a while.

This page shows how to narrow it down, how to measure your pressure, what you can fix, and when to call the utility, a plumber, or a well contractor. No water at all in cold weather? See frozen pipes first.

First, Check What Is Normal

Pressure and flow are different. Pressure is the force behind the water, in pounds per square inch (psi); flow is how much comes out. Portland Water Bureau notes that what feels like low pressure is often low flow: a clogged faucet or old corroded pipes choke the flow while the pressure is normal. A leak or a service disruption in the neighborhood lowers the pressure itself.

Pressure varies. It dips at peak times, before and after work hours and in summer, and depends on your home's elevation compared with the utility's tank. Portland keeps most homes between 40 and 80 psi, though some always get less. Your utility can tell you the range for your address.

The codes set a ceiling. Watts, which makes pressure-reducing valves, notes that the IPC and UPC plumbing codes require one when city main pressure exceeds 80 psi, and that the valve usually holds the house at 50 psi. The Las Vegas Valley Water District says most plumbers recommend a setting of 35 to 60 psi. The valve can only lower pressure, never raise it above what the street delivers.

Narrow It Down

Run every faucet, hot and cold, plus an outdoor spigot.

One faucet or showerhead. Start with the aerator, the screen at the tip of the spout, where Moen says debris and mineral deposits collect and restrict flow. Unscrew it and rinse it; on a pull-down faucet, also rinse the screen where the hose meets the spray wand. Moen says to make sure the faucet gets full pressure from both supply lines, so check that neither stop valve under the sink is partly closed. If it is still weak, Moen says the cartridge needs replacing. For a crusted showerhead, Kohler suggests a few hours' soak in vinegar, in a bag tied around the head if it does not come off, then a scrub. A shower that stays weak may have a faulty valve in the wall, a plumber's job per Kohler.

Only the hot side. A.O. Smith says that when the water heater causes low pressure, it is typically a blocked or damaged shutoff valve, so make sure the valve at the heater is fully open. Portland adds checking the heater for leaks and cleaning hot-side aerators. A.O. Smith recommends a yearly flush, and our flush guide walks through it. If hot flow is still weak, have a plumber look at the heater.

Every faucet, including outside. That is a whole-house problem; the causes below are in checking order. First, ask a neighbor whether their pressure is down too, and look for a notice on your door or crews in the street. The Fort Collins-Loveland Water District says low flow across a whole neighborhood can be a sign of a neighborhood leak and asks customers to report it on its emergency line. Call your utility and follow any notice it issues.

How to Measure Your Water Pressure

A gauge tells you whether pressure or flow is the problem. Rain Bird's steps: screw the gauge onto the faucet nearest the water meter, make sure no water is running anywhere inside or outside the house, then open that faucet and read the gauge. Pressure changes through the day, so take readings at a quiet hour and a busy one, and write them down.

A normal reading with weak faucets points to a flow restriction: aerators, a filter, a partly closed valve, or old pipes. A reading well below your utility's range is worth a call to the utility. A reading above 80 psi is over the code limit and needs a pressure-reducing valve installed or adjusted by a plumber; Watts notes that banging pipes and water splashing out of the sink are signs of excess pressure (see banging pipes).

Watts lists it as not lead-free, so use it as a test tool: screw it on, take your readings, and take it off.

Most Likely Causes

1. The main shutoff is not fully open. After plumbing work the main valve is sometimes left partly closed, the Fort Collins-Loveland district notes, and the Las Vegas Valley district says even a slight closure restricts flow. Find it with our main shutoff guide, which shows how each type turns, and open it fully. Portland says to check that every valve in the house is all the way open. A valve that will not turn by hand is a plumber's job.
2. A whole-house filter or softener that needs service. Culligan says a filter cartridge loaded with particles restricts flow, lists a noticeable pressure drop as a sign it is due, and says to replace cartridges on the maker's schedule. For a softener, the Las Vegas Valley district suggests switching it to bypass: if pressure comes back, the softener probably needs service or replacement. Follow your model's manual for both.
3. A failing pressure-reducing valve. If your house has one, it is usually a bell-shaped valve on the main line; Moen says it sits next to the main shutoff, and the Las Vegas Valley district notes it can also be near the water heater or softener or outside between the house and the meter. The Fort Collins-Loveland district says a failed valve can reduce pressure and that sudden jumps or drops can point to it, and A.O. Smith calls a faulty one a frequent cause of low pressure. The Las Vegas Valley district says a licensed plumber should adjust it; Watts says a malfunctioning valve can often be cleaned or repaired with a service kit rather than replaced.
4. A leak. Turn off all water inside and outside, then look at the water meter's leak indicator, a small red, white, or blue triangle or a blue snowflake-shaped dial. If it is turning, water is flowing somewhere. The EPA's WaterSense program adds a slower test: read the meter, use no water for two hours, and read it again; any change probably means a leak. Then close your main shutoff and look again: if the indicator still moves, the Las Vegas Valley district says the leak is most likely underground between the meter and your shutoff. Meter lids can be heavy, and Portland warns that animals hide inside. A confirmed leak is a plumber's job.
5. Old galvanized steel pipes. Portland says corrosion in older galvanized plumbing can restrict flow. There is no homeowner fix; replacing the pipe is a plumber's job.
6. On a private well: the pressure tank or switch. The pressure switch starts the pump at a cut-on pressure and stops it at a cut-off pressure, typically 20 psi higher per Pentair, and both Pentair and Amtrol set the tank's air charge 2 psi below cut-on. If the pump now runs in shorter cycles than it used to, Amtrol says the tank may have lost air, which can mean internal corrosion, and warns that adding air to such a tank can make it rupture or explode, possibly causing serious or fatal injury, so leave its air valve alone. Amtrol calls for a yearly check by a licensed professional; this is a call to a well or pump contractor.

What You Can Fix Yourself

• Clean aerators, the pull-down wand screen, and showerheads.
• Open the sink stop valves, the heater valve, and the main shutoff fully, without forcing them.
• Change a whole-house filter cartridge or bypass the softener, per the manual.
• Measure your pressure with a gauge and write it down.
• Run the meter leak test.

When to Call a Pro

Call the utility when the neighborhood is low too, when you have no water and no shutoff notice, or when your gauge reads well below your address's expected range. Portland and the Las Vegas Valley district both say they cannot adjust pressure for a single home; if your address is supposed to get less than 40 psi, Portland says you may choose to install a booster pump.

Call a licensed plumber for a pressure-reducing valve, a reading above 80 psi, a confirmed leak, a shower valve, weak hot water after the heater valve check, a stuck main shutoff, or galvanized pipe. On a well, call a licensed well or pump contractor; the EPA advises making sure pump installers are bonded, insured, and licensed where your state requires it.

Prevent It

Clean aerators when flow drops, and turn the main and fixture valves once a year so they do not seize. Replace filter cartridges on the maker's schedule, flush the water heater yearly, and on a well, book the yearly professional check. Keep your gauge readings to spot a slow decline, and put leak sensors by the water heater and washer.

Frequently Asked Questions

What is normal water pressure for a house?

Portland keeps most homes between 40 and 80 psi, Watts says a pressure-reducing valve usually holds a house at 50 psi, and plumbers commonly recommend 35 to 60 psi, per the Las Vegas Valley Water District. The codes require a pressure-reducing valve above 80 psi. Ask your utility what your address should get.

Why did my water pressure suddenly drop?

Common causes are a main valve left partly closed after plumbing work, a failed pressure-reducing valve, a leak, or a main break on the utility's side. Ask a neighbor, check the main valve, and run the meter test.

Why is the water pressure low in only one faucet?

Look at that fixture: a clogged aerator or wand screen, a partly closed stop valve under the sink, or a cartridge that needs replacing, per Moen.

Does a whole-house filter lower water pressure?

Slightly. Aquasana says a small decrease in flow is normal with any filter, but a noticeable or sudden drop signals a problem, and Culligan lists a noticeable pressure drop as a sign the cartridge is due.

The Bottom Line

Find where the weak flow is first. One faucet means the aerator, stop valve, or cartridge; hot side only, the heater's valve, then the heater; the whole house, the main valve, a filter or softener, the pressure-reducing valve, a leak, old pipes, or a well's tank and switch. Ask the neighbors, measure, and leave pressure-reducing valves, leaks, pipes, and well equipment to a licensed pro.

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