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Question DetailsAsked on 10/9/2013

when installing a pressure reducing valve it is State Code to install expansion tank at water heater, correct?

I need to install a water pressure regulator valve to reduce the water pressure in a home. I was quoted $1500 and told I need this in conjunction. I have done this before without the expansion tank. Why do I need it?

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2 Answers


Just like the pressure regulator keeps the pressure at or under a certain psi coming into your home it also can keep excess pressure from leaving your home. You need to protect against back pressure from your home that now can no longer be dissipated to the city service lines. When water heats it expands. It then creates additional pressure due to that expansion. The tank allows that expansion to occur without building additional pressure in your lines. My thoughts on it are that in most cases the tank is an extra precaution for something that shouldn't be a big concern. But suppose you have a weak joint or pipe. Do you really want to take that chance? The purpose of the regulator is to keep the pressure down so adding pressure back on the system negates having one installed at all. In theory, every time the water heater warms up it adds a little more pressure to the system. Under normal use the added pressure shouldn't build to a point of danger. When you leave for a few days, however, that pressure can slowly creep up until something gives. Then water flows all over your house until you get home to find it.

$1500 for a pressure regulator and an expansion tank may be a little steep but your area may be more expensive than others. Call a few other plumbers for second and third opinions as well as bids to do the work. Plumbers aren't cheap but installing these devices is not that difficult, in most cases, either.

Answered 7 years ago by Todd's Home Services


$1500 ? Are you kidding, or did you slip a digit ?

Around here (in a high cost area) a pressure regulator and expansion tank would run about $100-150 parts plus about $125-150 labor, installed in a normal house with working room - of course more if really tight working room or goofy plumbing, which might occur in about 10% of jobs.

You need to get 2 or 3 more quotes - Search the List (in green banner bar) for local plumbers with good ratings and reviews.

Answered 7 years ago by LCD

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