One Fixture or the Whole House?
This is the first question, because it sorts the problem in half:
- One faucet or shower is weak: Usually a clogged aerator, showerhead, or cartridge at that fixture. Start with the aerator; we have a five-minute guide for it.
- Hot water is weak but cold is fine: Points to the water heater side: a partly closed valve, sediment, or a scaled tankless unit.
- The whole house is weak: Points to the pressure reducing valve, the main shutoff, the service line, corroded interior piping, or the supply from the utility.
What a Pressure Reducing Valve Does
Many homes get water from the street at a higher pressure than household plumbing should see. A pressure reducing valve (PRV), usually a bell-shaped brass valve near where the main line enters the house, drops that pressure to a steady level for the house. The plumbing code Washington adopts requires a pressure regulator when static pressure exceeds 80 psi, and an expansion tank downstream of it to handle thermal expansion from the water heater (UPC 608.2).
PRVs wear out. When one fails it can go either way:
- Pressure drops: The valve sticks partly closed or its internal strainer clogs. The whole house goes weak.
- Pressure creeps up: The valve stops regulating and lets street pressure through. You see banging pipes, running toilets, dripping faucets, and a relief valve on the water heater that discharges.
How We Diagnose It
- Static pressure test with a gauge at a hose bib or laundry connection.
- Check whether pressure climbs overnight, which points to a failing PRV or a missing or dead expansion tank.
- Check the main shutoff is fully open and the PRV strainer is clean.
- Look at the supply piping. Galvanized steel narrows from the inside as it corrodes, and no valve fixes that.
- If pressure is low before the PRV too, the problem is the service line or the supply, and we tell you which.
When It Is Not the Valve
- Corroded galvanized supply piping: The fix is a repipe, not a new PRV.
- Leaking or undersized service line: See water line replacement.
- Low supply from the street: If pressure is low at the meter, the utility is the first call. We can document the reading for you.
What's Included and What's Not
PRV replacement includes the valve, unions or fittings to connect it, setting the outlet pressure, and checking the expansion tank. A new expansion tank, main shutoff valve, or repiping is quoted separately if we find it is needed. Work on the utility's side of the meter belongs to the utility.
What It Costs
Flat-rate, quoted after the gauge test and before any work. No trip charge in our service area.