Question 1

How do I know when to replace my PRV?

Accepted Answer

Simply stated, it is a code requirement. If you have a Pressure Reducing Valve (PRV) being added and/or it is being replaced due to age or problems, then we will also need to inspect your water heater for the presence of an expansion tank. Depending on its age and condition it might need to be replaced.

Having or installing a PRV creates what plumbing code defines as a “closed system.” Without getting into the semantics of what that means, just know that when this code was adopted around 2017, thermal expansion tanks were then required to be installed when a storage tank hot water heater was present.

So, if you have a traditional storage tank water heater(s), then by code you must also have an expansion tank. In contrast, an expansion tank is NOT required for a home with a tankless water heater. That said, it’s not a bad idea to have one if excessive water pressure is common in the water entering your area.

Question 2

What does a pressure reducing valve do?

Accepted Answer

The simple answer is that it does exactly as the names says; it reduces the incoming water pressure. It allows the municipality to pump in water at higher than normal pressures, and/or more than a typical domestic water system is designed to handle.

There are two primary reasons for this increased pressure. One is to serve larger square footage homes, and the other is so that residents and businesses don’t experience significant or noticeable pressure decreases during high-demand times of the day and night.

For example, most neighborhoods in Frisco and McKinney are in the 90-100 PSI (pounds per square inch) range at the street. Some areas on the western side of Frisco (ex: Teel Parkway between Lebanon & Eldorado) often exceed 125 PSI. There are some areas in Plano (North along 121 and northwest along the NDT) where the homes exceed 85 PSI. In that case, you might not have a PRV but need one, and you may be eligible for a $500 rebate through the city.

Normal or ideal water pressure is usually around 75-80 PSI. Anything above 85 PSI is too much pressure for the house and the various fixtures and/or appliances to handle. Toilet fill valves are especially affected when the cold water pressure is over 85 PSI. So, the PRV is required to reduce the incoming water pressure before it enters the home. This reduces the likelihood of pressure-induced leaks and/or ruptured water lines that can cause catastrophic damage—as well as the weird phenomenon known as “water hammer.”

Staying with our example cities of Frisco and McKinney, any home that was built in 2000 or later should have a Pressure Reducing Valve (PRV) by city plumbing code. Some larger homes that were built in the late 90s (ex: Starwood) will also have them.

Back in the early days of the PRV requirements, the builders installed them on the main water lines right before water entered the home. Because of this, they are often buried and/or obscured by mature landscape. Most homeowners do not even know that PRVs exist until they experience a high- or low-pressure problem, or they form a leak. In fact, you may be one of the many people reading about PRVs for the first time here.

Question 3

Where is the PRV located?

Accepted Answer

Generally (with the exception of certain neighborhoods), for homes built between 2000 and approximately 2014-2015, PRVs (and your main whole house shut off valve) have a valve box (sometimes two) located to the left or the right of the double cleanout for the home.

The double cleanouts are those two white pipes that are sticking up out of the flower bed. Those allow plumbers to access your main sewer line going under the home and to the street if there is a clog. Usually, in an attempt to avoid additional digging, most of the new construction plumbers would often install the main water line in that same excavated trench. Sometimes we have to use locating equipment to find these buried water lines and then exploratory digging to find the PRV (and shut off the flow).

Starting in about 2014-2015, common sense began to prevail in the new home builder trades. They gradually began to relocate the PRVs (and main shut off valves) into the garages or utility closets and sometimes the laundry rooms.
By 2016-2017, the practice of installing these two critical devices outside, buried underground, and rarely accessible was pretty much nonexistent. In all homes being built right now, the PRV and shut off valve is typically located inside the wall behind an access panel or fabricated cabinet door.

This makes everything very accessible, which is important for two reasons. The PRV may need to be adjusted up or down through the years, and the whole house water shut off valve needs to be readily and easily accessible in case of an emergency water leak scenario.

Although rare, we will occasionally see a PRV (and shut off valve) in the garage of a house that was built in the late 1990s and early 2000s. When we do run into it, it seems to be more common in larger homes over 5,000 sqft and/or multi-family homes (condominiums, duplexes, and townhomes).

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