Plumbing tips · November 12, 2026
The bell-shaped valve on the main line, and how it fails
A pressure reducing valve takes the high pressure coming from the street and turns it down for the house. When it wears out, the pressure can go wrong in either direction.
Where it is
Look on the main water line close to where it enters the house, often just after the main shut-off: in the garage, a closet, a utility room or a box outside near the foundation. It is a brass valve with a bell or dome on top and an adjusting screw with a lock nut on the bell.
How it fails
The seat and diaphragm inside wear over the years. Most often the pressure creeps up and past where it was set, which shows as running toilets, dripping faucets and a weeping water heater relief valve. It can also fail the other way and starve the house, with weak flow everywhere at once.
Other signs
Pressure that swings up and down, a humming or chattering from the valve when water is running, or water seeping from the bell. A gauge on an outside faucet is the quickest way to see what it is actually doing.
Adjusting it
Turning the screw in raises the pressure and backing it out lowers it, a little at a time, checking with a gauge as you go. If it will not hold a setting, or the pressure keeps climbing, the valve is worn and needs replacing rather than adjusting.
Questions we get asked
Does every house have one?
No. A house only needs one where the pressure from the street is high. If the house has no valve and the gauge reads over 80 psi, one should be added.How long does a pressure reducing valve last?
Many years, but not forever. Hard water and grit wear the parts inside faster. When the pressure starts drifting, it is usually time.Why did my water heater start dripping after a new valve went in?
A pressure reducing valve stops the water heater pushing its expansion back to the street. Without an expansion tank, that pressure has nowhere to go, and the relief valve lets it out.Plumbing questions we answer
Where we go
Parker, Wise and Tarrant County, out of the shop in Springtown. Springtown, Weatherford, Azle, Boyd, Decatur, Newark, Millsap, Fort Worth and the country in between.
Call 817-487-8866