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St. George Home Services

Plumbing · Repairs and leaks

Water pressure too high

Incoming pressure that is too high, measured and then brought down to where the house can live with it.

One flat fee to find out what is wrong. You are told it on the phone before anyone is dispatched, and it comes off the job if you hire us. Read our Plain Terms

A new copper main water service line run from the meter into the house
A new main water service. Southern California.

What the work is

High static pressure is quietly expensive. It shortens the life of every flexible connector, every fill valve and every cartridge in the house, and it is the reason behind a lot of failures that get blamed on the fixture.

The first thing is the measurement. We gauge the static pressure at a hose bibb and tell you the number. If it is high, a pressure reducing valve on the service brings it into range.

Fitting one turns the house into a closed system, so a thermal expansion tank has to go on at the same time. Anyone who fits a reducing valve and does not deal with expansion has created a new problem.

What is included

  • Measuring and reporting the static pressure in writing
  • The valve, installed on the service with a union so it can be serviced
  • Setting the outlet pressure and showing you the gauge
  • Fitting or checking a thermal expansion tank at the same time
  • Re-measuring at a fixture afterwards

What is not

  • Replacing the water service itself
  • Repairing fixtures that were already damaged by the high pressure
  • Adjusting a valve someone else installed without checking the rest of the system

If your relief valve drips and then stops

That is thermal expansion, not a faulty valve, and it appears as soon as a house becomes a closed system. The guide below explains the sequence. It is the most common thing we are called out to that has already been 'fixed' twice.

What to ask anyone quoting this, us included

  • What is my static pressure, in numbers?
  • What did you set the valve to?
  • Is there an expansion tank, and is it charged to that pressure?

What we can show you in writing

Every line traces to a document we read in full. The number after a sentence points to the research below.

  • A pressure-reducing valve or a backflow preventer at the service entrance turns the house into a closed system. Heated water expands about 2 percent and has nowhere to go, so pressure reaches the T&P setpoint of 150 psi inside one heating cycle.1
  • If the T&P valve at the water heater drips for a while and then stops, that is thermal expansion, not a failed valve. St. George requires backflow assemblies on outside watering systems and pressure-reducing valves are common, so a lot of houses here are closed systems.1
  • Static pressure gets measured before anything is set. An expansion tank is precharged to the pressure that was measured — a factory 40-psi precharge left on an 80-psi system does nothing from the first day.1

Where this comes from

Every line above traces to a document we read in full. The number after a sentence points to the research below; hover it for the section. If you find a line wrong, tell us and we will fix it and say so.

  1. Plumbing research, August 2026 Compiled from manufacturer warranty documents and installation manuals (A.O. Smith, Noritz, Rinnai, Rheem, Navien, Bradford White), the Battelle / Water Quality Research Foundation study, the Utah Code and DOPL rules. 1 section cited. Hover a number above for the section.

Read before you decide

The rest of repairs and leaks

The quote is the number. There is no second number.

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