That's a bit high. There should be an adjustment screw on the PRV to set the pressure.

90-100 psi at the street is no big deal (my own street pressure is 127) but it IS a big deal in the house. You need a PRV but the one you have almost certainly is capable of reducing your pressure to an acceptable range. (I adjusted mine to 65psi) I would be surprised if you're out of its adjustment range. Weedmeister is correct....there should be an adjustment screw on it that allows you to dial it down.

Also, as I learned on this forum some years ago, presence of PRV leaves you with a "closed" system. If you don't have an expansion tank next to your water-heater, you will want to have one installed. Not having one will shorten that device's life and also put the rest of your system at risk. I can tell you from experience that it's not a risk worth taking.

Thanks all. I found a video on YouTube from Watts that shows how to adjust the PRV installed at my new house. Interesting that the plumber did not mention the PRV can be adjusted; he just said it needed replacing. Upselling anyone?

If I can adjust this Watts PRV and reduce the pressure, then this plumbing company is not getting any of my business!

Thank you about the expansion tank. There is an expansion tank on the radiant floor heating boiler, but that portion of the system can be closed off from the rest, so it seems I still need an expansion tank on the hot water heater. I will check now; another post says it should be located on cold water supply to WH. NOTE plumber did not mention this issue.

You're not alone. In my turn, I had to instruct the plumber, his supervisor, and the damned city inspector!

This information first came to me here from justalurker...and he was absolutely correct. Every one of these individuals was self-admittedly embarrassed at their oversight.

FYI: PRVs can break, or can get clogged. Mine did, and I found it easier to replace than to purchase the kit with the washers and gaskets, disassemble and repair. Mine is located in the utility room where the main line comes into the house. Other jurisdictions put it on the meter out at the curb, which is much harder to deal with.

The plumber was not upselling, I did need a new PRV. I tried adjusting it but it did nothing. Water pressure remained 110 psi. I had the plumber install a new PRV yesterday and pressure is now 60 psi. It is good to learn how these things work, though. My plumbing system looks like a U-Boat with all the pipes for radiant heat so it is good to understand it all.

Plumber did not think an expansion tank is needed, said it is not code, and that if an expansion tank were installed, it should be on the hot outlet from water heater.

People on this forum have said to install expansion tank on cold supply side to WH. Anyone have a link to proposed plumbing code(s) to resolve this?

IIRC addressing thermal expansion in closed plumbing systems (and your PRV makes your system CLOSED) has been code required since the mid 90's. Your plumber needs to re-read the plumbing code or print this for him...

http://www.watts.com/pages/learnAbout/thermalExpansion.asp?catId=64#generalinfo_plumbingcode

And here's the installation guide showing WHERE to install the expansion tank...

http://media.wattswater.com/2915054.pdf