Do I need a Pressure Reducing Valve / Expansion Tank?

13 years ago

Please help me! I don't know what to make of my situation. I know very little about plumbing. Most of what I describe below I have learned in the past couple of weeks.

My house is 14 years old and I have experienced two slab leaks in the past nine months. I am trying to understand if this was just a dose of bad luck or if there is an underlying cause(s) behind it. It is probably not easy to pinpoint the cause of slab leaks since there are so many underlying factors that can contribute to it. A primary suspect right now is high municipal water pressure. I purchased a water pressure gauge and connected it to the bib outside. The lowest reading I get is 80 psi. The pressure will often rise to 90-94 psi. I left the gauge connected overnight and it recorded a peak reading of 98 psi. I learned that as communities grow, instead of upgrading the infrastructure ($$$), cities will often resort to the easy fix which is to crank up the pressure.

How big of an issue are the readings I am getting? In researching several plumbing forums I have read that anything above 80 psi stresses out the pipes and should be avoided, and that the ideal static pressure in your home should be no higher than 70 psi? I am not counting on the city to resolve my problem. Is there enough justification for me to consider installing a Pressure Reducing Valve (PRV)? And if so, this leads me to a whole new set of questions dealing with thermal expansion. I have a 50 gallon gas water heater. Right now, the increased water volume resulting from TE finds its way back into the municipal supply because the setup allows it. Once a PRV is installed, however, I will create a "closed system" situation that could make matters worst if not done correctly? If for instance the water pressure will now have to work its way to 80 psi and beyond before a relief is triggered within the system (either through the water heater's T&P valve or the PRV itself) then it becomes a mute point to install a PRV in the first place. Am I missing something? I have read that some PRVs incorporate a thermal expansion feature, but I don't know this works. I have started to read about expansion tanks. It almost seems like if I install a PRV, I must also get an an expansion tank installed if I want to do it right and address the TE concern?

Thank you.

Comments (7)

brickeyee
13 years ago
What type of piping?

Copper should have no pro0blems at all with the pressures you have.

Even plastics are rated well above.

Corrosion damage is not going to be fixed by reducing the pressure.

Most of the problem with higher pressure is problems with valves, not the piping itself.
User
13 years ago
Have you ever checked the PH of your water? If you have copper pipes that can be your problem.

IIRC check valves at the water meter have been code since sometime in the mid 90s so you should have a check valve at your water meter right now giving you a closed plumbing system.

If you don't, then installing a PRV will definitely give you a closed plumbing system and you will need a thermal expansion tank.. It is up to you to protect your plumbing, appliances, and fixtures from excessive water pressure.

The T&P valve on your WH is NOT a pressure relief device it is a SAFETY device and repeated activation will compromise the valve's intended ability which is to protect you from an explosion..

Here's the Cliff's Notes on thermal expansion... http://www.watts.com/pages/learnAbout/thermalExpansion.asp?catId=64
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asolo
13 years ago
The good news is that PRV's and expansion tanks are quite common and not hideously expensive even if hired done. I had both installed at my place (street pressure 127psi!) a couple of years ago. As I recall, parts and labor came in somewhere either side of $400.00. They did everything, I did nothing. Interestingly, however, none of them seemed up to speed on closed systems or expansion tanks. Even city inspector was clueless....but agreed instantly when I described. ( Justalurker clued me in on all of that.) I specified what I wanted, had it done, and all my problems went away.

If you're on city water, I doubt you'd have corrosion problems but those slab leaks certainly would make me look at everything.
lazypup
13 years ago
QUOTE "I learned that as communities grow, instead of upgrading the infrastructure ($$$), cities will often resort to the easy fix which is to crank up the pressure."

I find that statement extremely hard to believe because cities do not use pumps to generate the pressure. Municipal water pressure results from static head pressure developed by water towers or locating storage tanks on high elevations within the community. The municipal supplier uses pumps merely to keep the storage tank full.

In fact, quite the opposite is true. In many instances the municipal line pressure increases as a result of the city replacing old lines with new lines that are larger in diameter which then results in less friction head from the source to the point of demand, ergo the pressure at the demand is higher.

The municipal supplier is not required to provide PRV's. When ever a new installation is set in place the municipal supplier is required to make a tap into the municipal line and run a short section of line from the tap to the "Curb Stop" valve.

The property owner is then responsible to install a code approved "Supply Line" from the curb stop to the structure, and all "Distribution Piping" within the structure.

In instances where the volume will be measured by means of a meter the municipal supplier will inform the builder where the meter will ultimately be located and they five you a "Fitting allowance" measurement. You are then required to cut out a section of the supply line equal to the fitting allowance length, and in some jurisdictions the homeowner is required to install 1/2 of a meter union on each open end of the line. After the line is inspected the municipal suppliers personnel will supply and install a meter in that opening.

Under both the IRC & UPC in instances where the static head pressure exceeds 80psi the homeowner is required to install a PRV (pressure reducing valve). (IRC-2903.3.1 & UPC 608.2)

Under both the IRC & UPC either the valve must have an integral bypass for thermal expansion or you must install an expansion tank. (IRC 2903.4 & UPC 608.3).
jph1
13 years ago
You should install a PRV and water heater expansion tank. You could easily do this yourself with the aid of sharkbite fittings in less than 1 hour. I would expect your invested costs to be about $150 or less. It is very easy and with these fittings, a 10 year old child can install these for you.
Many PRVs are now coming with these sharkbite fittings pre-installed to make it even easier.
Let me know if you need assistance. JPH1
Carla Villanueva
8 years ago
The Question and Comments are very helpful, especially for a novice like me. I have a 10-unit apartment complex, (2 bldgs) built in the 60's. We bought this property 10 years ago. Few months ago, we had a slab leak. It was suggested to me to install a water pressure regulator; current psi is about 110-120. I have talked to a number of plumbers; some said yes and some said i dont have to. Now that i have decided to install one, this one plumber is telling me that i shd also install a thermal expansion (tank/valve??) Do i really need to install a thermal expansion (valve/tank??) This work will cost me about $1300-$1500? Is that reasonable fee? Your expert advice will be appreciated.
User
8 years ago
Carla,

If you install a PRV then code (since the 90's) requires either a bypass at the PRV or an approved thermal expansion device

Re-read my post in this thread and also the post by Lazypup (an experienced plumber). All your answers are in those two posts.

Do I need a Pressure Reducing Valve / Expansion Tank?

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brickeyee

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