Quick Answer:
If the whole house has weak pressure, including hose bibs, the pressure reducing valve (PRV) is a common cause. Quickly check pressure at three or more fixtures, read a gauge at an outdoor hose bib, confirm the meter and main shutoff are fully open, inspect the PRV screen/strainer if you can, and test one faucet with its aerator removed. If multiple fixtures and the hose bib gauge read low, the PRV or upstream blockage is likely the problem.
Why This Happens
A PRV is designed to lower incoming water pressure to a safe level for your plumbing. Over time it can get clogged by sediment, the internal diaphragm can wear, or the valve can stick. A clogged screen or strainer just ahead of the PRV reduces flow, and a failing diaphragm or seat can limit pressure across the entire house. Heavy sediment conditions increase the chance the valve becomes restricted—see PRV clogged by sediment for more on how that happens.
Step-by-Step What to Do
1. Confirm low pressure at 3+ fixtures
- Run the kitchen sink, a bathroom sink or shower, and an upstairs fixture (or another distant tap). Note the flow at each.
- If all three show clearly reduced flow, that points to a whole-house supply issue rather than a single fixture.
2. Read a gauge at the hose bib
- Attach a simple garden hose pressure gauge to an outdoor hose bib and open the valve fully. Record the psi reading.
- If the hose bib gauge reads low and you saw low flow at multiple fixtures, the PRV or supply is likely responsible.
3. Verify meter and main shutoff are fully open
- Locate the water meter and main shutoff (often near the meter or where the service enters the house). Make sure both valves are fully open — quarter-turn ball valves should be parallel to the pipe; multi-turn valves should be turned fully counterclockwise until they stop.
- Do not force a stuck valve. If it won’t open easily, stop and call a pro.
4. Check the PRV strainer/screen if accessible
- Locate the PRV (usually just after the main shutoff). Many systems also have a small strainer or screen ahead of the PRV that traps sediment.
- If the screen is accessible and you are comfortable working on plumbing: shut off the main, open a faucet to relieve pressure, then remove and inspect the screen. Clean and replace it if clogged.
- If you’re unsure where the PRV or screen is, or it’s hard to reach, stop and consider professional help.
5. Test with an aerator removed at one faucet
- Unscrew the aerator from a visible faucet and run the water. If flow improves significantly at that faucet but not others, the problem may be a clogged aerator or fixture-specific blockage rather than the PRV.
- If flow stays low everywhere, the issue is upstream.
6. Extra checks
- Look for leaks that could be reducing pressure when multiple fixtures run.
- If you have a bypass or isolation valves around the PRV, note their positions but don’t force them; a controlled bypass test may help a plumber diagnose the valve.
- For a more thorough diagnosis, consult guidance on How to test PRV failure.
What Not to Do
- Don’t keep cranking the PRV higher—if it’s clogged, you’ll just stress the diaphragm.
- Don’t try to remove or replace the PRV without first shutting off the main and relieving pressure.
- Don’t force stuck shutoff valves or use heat/corrosive cleaners on plumbing parts.
When to Call a Professional
- If the hose bib gauge and multiple fixtures read low after the checks above.
- If the PRV is leaking, noisy, or you cannot access the screen/strainer safely.
- If cleaning the screen doesn’t restore pressure or the PRV needs replacement—PRV replacement requires proper sizing and sometimes permits.
Safety Notes
- Always shut off the main and open a downstream faucet to relieve pressure before working on the PRV or removing a screen.
- Wear eye protection when flushing sediment from screens; water can spray unexpectedly.
- If you’re unsure about any step, stop and call a licensed plumber to avoid water damage or injury.
Common Homeowner Questions
- How do I know it’s the PRV and not the city supply? If an outdoor hose bib gauge and several indoor fixtures all read low, the PRV or your service line is likely at fault. If only the gauge reads low but neighbors have normal pressure, contact the utility.
- Will cleaning the screen fix it permanently? It can restore flow if sediment caused the restriction, but recurring sediment or a worn PRV may mean replacement is needed.
- Can I replace the PRV myself? Technically possible for experienced DIYers, but it requires shutting the main, draining lines, correct sizing, and sometimes a permit—hire a plumber if you’re not confident.