To increase water pressure safely, measure it first. If static pressure is low and you have a pressure reducing valve, raise its setting a little at a time, never past the 80 psi code limit. If pressure is fine but flow is weak, clear valves, softeners, scale or aerators. Low street pressure calls for a booster.
Step 1: measure static pressure
Screw a pressure gauge onto a hose bibb near where the water line enters the building, or onto the washing machine's cold water connection. Turn off everything that uses water, open the valve fully and read the gauge. The EPA's WaterSense program describes the same test.
Then compare:
| Reading (static) | What it means | Where to go |
|---|---|---|
| Under 40 psi | Low. Below what Phoenix calls acceptable | Check the PRV, then the street |
| 40 to 45 psi | On the low side | A small PRV adjustment may help |
| 45 to 60 psi | The range WaterSense recommends | Pressure is fine; look for flow restrictions |
| 60 to 80 psi | High side of normal | Don't raise it; look for restrictions |
| Over 80 psi | Over the code limit | Needs a working PRV, not more pressure |
WaterSense recommends incoming pressure "between 45 and 60 psi to ensure efficient use of water and proper system function." Phoenix's customer page calls 40 to 100 psi acceptable at the meter, but the plumbing code caps pressure inside a building at 80 psi (IPC 604.8). Our page on what your home water pressure should be covers the ranges in more detail.
Step 2: if pressure is low, adjust the pressure reducing valve
If your reading is low and you have a pressure reducing valve (PRV), it may simply be set low. PRVs have an adjusting screw or bolt, usually on top of the bell-shaped housing, with a locknut that holds the setting.
Here's how to raise it safely:
- 1Put the gauge on first so you can see what each turn does.
- 2Loosen the locknut on the adjusting screw.
- 3Turn the screw a little at a time. On most direct-acting valves, turning it clockwise raises the setting. Check the maker's instructions for yours.
- 4Open a faucet, then close it, and let the gauge settle after each change.
- 5Stop in the 45 to 60 psi range, and never above 80.
- 6Tighten the locknut and recheck the reading an hour later.
If turning the screw doesn't change the reading, the valve is worn or its strainer is clogged. The code requires a PRV to be installed "with strainer," and a packed strainer can starve the whole house. Our page on the signs a pressure reducing valve is going bad covers that, and whether you need a pressure reducing valve explains why the valve is there in the first place.
### Check expansion control after raising it
A higher setting leaves less room before the water heater's thermal expansion pushes the system too high. IPC 607.3 requires a thermal expansion device on the water heater's cold supply wherever a PRV, check valve or backflow preventer makes a closed system, sized so pressure stays within the 80 psi limit. If your relief valve starts dripping after you raise the PRV, the expansion tank may be failed or undersized. See why water pressure suddenly gets too high for the checks.
Step 3: if pressure is fine, clear the restriction
A gauge reading of 55 psi with weak showers means water is getting held up somewhere. Phoenix's water services page lists the usual suspects: mineral buildup in galvanized plumbing, a water softener that needs maintenance, a partially closed house valve and debris in faucet aerator screens.
Work through them in order of effort:
- Open every valve all the way. Check the main shutoff, the valve at the meter and the valves around a softener or filter, especially after recent work.
- Bypass the softener. If pressure jumps with the softener in bypass, it needs service. See whether a water softener reduces water pressure.
- Clean aerators and showerheads. Hard water scale builds up fast. Our page on why shower water pressure is low covers the shower side.
- Look at the pipe. Galvanized steel narrows inside as it scales. If the home still has it, repiping is the lasting fix.
- Check the pipe size. The IPC requires pipes sized so fixtures get their minimum flow "under conditions of peak demand." If pressure sags only when two fixtures run, see why water pressure drops when two fixtures run at once.
Step 4: if the street is low, add a booster
Sometimes the water just isn't there at the meter. In Phoenix, the city's design manual says pressure zones provide "a minimum of 40 psi at the customer's meter," but only where the property sits within its zone's elevation range. Above that range, "the developer/owner is required to install a private booster facility." Our page on why water pressure is different across Phoenix explains the zones.
The plumbing code covers the same case. IPC 604.7 says that wherever street pressure "is insufficient to provide flow pressures at fixture outlets" as the code requires, "a water pressure booster system ... shall be installed." A booster is a pump and controller on the main line, and it's sized to the building's demand. See whether you need a water booster pump for how that works.
### In a commercial building
Commercial restrooms raise the bar. The IPC's design table lists flushometer toilets at 35 to 45 psi of flow pressure at the fixture, and a flushometer urinal at 25 psi, compared with 20 psi for a tank toilet. Upper floors lose pressure to height, and long runs lose it to friction. The code also says that where street pressure fluctuates, the building's system "shall be designed for the minimum pressure available" (IPC 604.6), so a building that works at noon but struggles in the morning rush may have been sized for an average instead of the minimum. The fix there is usually a booster system sized by a designer, sometimes with pressure reducing valves on lower floors so they don't get too much. Raising one PRV at the service entrance usually won't solve a building-wide flow problem.
If your reading at the meter is consistently low, tell the city first. Phoenix says issues "from the street to the water meter" are its responsibility.
### What not to do
- Don't go over 80 psi. WaterSense warns that high pressure "can damage plumbing piping, fixtures, and appliances" and raises the risk of leaks.
- Don't pull the flow restrictor out of a showerhead. Our page on why shower water pressure is low explains why that backfires.
- Don't touch the city's meter valve to "open it up." That's city equipment.
- Don't remove a working PRV because it seems to slow things down. The code requires it wherever static pressure tops 80 psi.
That's the order: measure, adjust, clear, then boost. HQ Plumbing and Air can test your pressure, service or replace a PRV, repipe scaled lines and size a booster, with free estimates and upfront pricing.