Quick answer
Low water pressure usually comes from a partly closed valve, clogged aerators, a failing pressure regulator, corroded pipes, a hidden leak, or a problem with the utility supply. Screw a gauge onto an outdoor hose bib to measure it. Cleaning aerators and checking valves is DIY-safe. Regulators, corroded pipe and suspected leaks are not.
Start by working out where the problem is
The pattern of the low pressure tells you most of what you need to know. Before you touch anything, walk through the house and note which fixtures are affected.
If one faucet or showerhead is weak, the cause is almost always at that fixture. If every fixture is weak, the cause is upstream, at the main valve, the pressure regulator, the supply pipe or the utility itself. If only the hot side is weak, look at the water heater and its shutoff valve.
- One fixture only: check the aerator or showerhead.
- Hot water only: check the valve on the water heater supply.
- Every fixture in the house: check the main shutoff, the regulator and the supply line.
- Sudden drop at every fixture: ask neighbors and check your utility for outages or main work.
The most common causes of low water pressure
The City of Bremerton, a Washington utility, lists several causes that apply to most homes. They are a good checklist for any property in western Washington.
- A partially closed shutoff valve, either the main valve or the valve near the water heater.
- Clogged faucet aerators.
- A failed or misadjusted pressure reducing valve, which shows up as low pressure at every fixture.
- A leak somewhere on the property.
- A water softener that is restricting flow. Bypassing it briefly is one way to test this.
- Rust buildup or flaking inside older galvanized steel pipes.
- Kinked, crimped or pinched water lines.
Elevation and the utility side
Not every pressure problem is inside your walls. Bremerton reports that pressure in its distribution system can range from about 30 psi to over 100 psi at the customer's meter, and that pressure changes by about 0.433 psi for every foot of elevation. Homes on higher ground generally see lower pressure.
If your pressure dropped suddenly and your neighbors have the same issue, contact your water utility. Bremerton notes that it cannot adjust pressure for individual properties, so check whether the problem appears only at your address.
What healthy water pressure looks like
Sources differ a little on the ideal number, so treat these as guideposts rather than a single rule. The Pacific Northwest National Laboratory advises that static service pressure should be no higher than 60 psi. Bremerton says most plumbers recommend a pressure reducing valve setting between 35 and 60 psi.
On the high side, most plumbing codes call for a pressure reducing valve when supply pressure exceeds 80 psi, and Bremerton warns that sustained pressure above 80 psi can damage toilets, dishwashers and washing machines. The sources we reviewed do not define a firm minimum. A reading well below the 35 to 60 psi range, combined with weak flow at every fixture, is a good reason to have the system looked at.
How to test your pressure with a gauge
A water pressure gauge is inexpensive and sold at home improvement stores. Bremerton suggests attaching it to an outside faucet or hose bib. Static pressure is the reading with no water running, so a few minutes of preparation matter.
Choose a time when you can control water use, and take a second reading later if the first looks odd.
- Turn off every fixture, appliance and irrigation line, and make sure no one is running the dishwasher or washing machine.
- Screw the gauge onto an outdoor hose bib and hand-tighten it.
- Open the hose bib fully and read the needle.
- Write down the number and the time, then repeat at another time of day.
- Compare the result with the ranges above.
How to check for a hidden leak
A leak can lower pressure and waste water long before a stain shows up. The U.S. EPA describes a simple meter test. Read your water meter, wait two hours without using any water, then read it again. If the reading changed, you likely have a leak.
Toilets are a frequent culprit and easy to check. The EPA suggests adding a few drops of food coloring to the toilet tank. If color shows up in the bowl within 10 minutes without flushing, the flapper is leaking. Flush right away so the tank does not stain.
A meter that moves with everything off is worth taking seriously. Leaks inside walls, under slabs or in buried lines are not something to hunt down by cutting into drywall yourself.
What is DIY-safe
Some checks are low risk and often solve the problem outright.
- Open the main shutoff and the water heater supply valve fully. Turn them slowly, by hand, and do not force a stuck valve.
- Unscrew faucet aerators, rinse out debris, and reinstall them.
- Look for kinked flexible supply hoses under sinks and behind appliances.
- Run the gauge test and the meter test described above.
- Bypass a water softener only if you know how, following its manual.
What is not DIY-safe
Some causes call for a licensed professional, either because the work needs tools and experience or because a mistake can flood the house.
- Adjusting or replacing a pressure reducing valve. Bremerton advises consulting a licensed plumber for installation and adjustment, and notes that owners are responsible for their own valves.
- Replacing corroded or galvanized pipe. Bremerton lists rust buildup or flaking in older galvanized steel pipes as a cause of low pressure, and that problem can be inside the walls.
- Chasing a leak you cannot see, especially behind finished surfaces or underground.
- Anything involving the water heater's gas or electrical connections. Pyper does not work on gas lines, so if you smell gas, leave the building and call 911 or your gas utility.
When to call Pyper Plumbing
If the gauge shows a pressure that looks wrong, the meter moves with everything off, or the whole house has weak flow after you have checked the valves and aerators, it is time for a professional look. Pyper Plumbing handles leak detection and repair, emergency repairs and repiping across Snohomish, Skagit, Whatcom and Island counties.
If you see water coming through a ceiling, hear running water you cannot account for, or the main line has failed, shut off the water at the main valve and call right away. Tell us what you found with the gauge and the meter. Those two readings help narrow the cause quickly.
Common questions
What is a normal water pressure for a house?
Sources vary. PNNL advises static pressure of no more than 60 psi, and Bremerton reports that plumbers commonly set pressure reducing valves between 35 and 60 psi. Many codes call for a pressure reducing valve above 80 psi.
Can a leak cause low water pressure?
Yes. Bremerton lists an on-site leak as a cause of low pressure. The EPA meter test, reading the meter before and after two hours with no water use, is a simple way to check.
Why is only my hot water pressure low?
Bremerton points to the water heater side, such as a partly closed shutoff valve near the heater, when only hot water is weak. Check that valve first, then call a plumber if it is fully open.
Can I adjust my own pressure reducing valve?
Owners are responsible for their valves, but Bremerton advises using a licensed plumber for installation and adjustment. A wrong setting can raise pressure and damage fixtures and appliances.
Sources
Facts in this guide come from the following references. Local rules and manufacturer instructions can differ, so follow your utility and your equipment manual.
- Water Pressure (City of Bremerton)
- Service Water Pressure (PNNL Building America Solution Center)
- Fix a Leak Week (U.S. EPA WaterSense)
This guide is general information, not a substitute for an on-site inspection. If you smell natural gas, leave the building and call 911 or your gas utility. Pyper does not perform gas line work.
