Hey folks. Working through plumbing overview course and I am performing an inspection of the public water supply.
My question is if there is no check valve or backflow preventor does a water regulator create a closed system? There is no expansion tank on the water heater.
That depends on the model of Pressure Reduction Valve and if you’re in a licensed State and what your licensing authority has to say about that (more on that shortly).
I’ll use a popular PRV we see here which is the Watts LFN45B LFN45B - Watts . If you read the documentation this valve is equipped with an integral bypass feature to help control thermal expansion on the downstream side (between valve and house plumbing). The valve will allow thermal expansion to be relieved by flowing back into the upstream side (main) if expansion pressure increases above the city supply pressure.
If you think about it there are potential issues with this but the issues are why the PRV is needed in the first place. However with the integral bypass valve it is no longer a closed system.
Now onto the “more on that shortly” aspect. Here in Texas our licensing authority has basically declared that any system with any PRV is a closed system regardless of if the PRV has the bypass function. So always follow your State SOP/rules when reporting on these things as they are the ones who can create you grief for no good reason.
Good to know.
Thanks for that. I haven’t found much help online.
Sounds like an expansion tank is a good idea either way?
Google can be your best friend, use it whenever you can to answer these questions.
I call them out on all systems that don’t have one installed.
Many homes in my area have the check valve installed downstream of the utility shut-off valve that many times is installed in the yard, and therefore aren’t visible.
Expansion tanks are always a good thing. However be prepared for blowback if you do call them out as missing. Just be sure you properly write your report to reflect the situation. For example:
A Pressure Reduction Valve (PRV) has been installed on the main water line for the home and no expansion tank was found for the water heater. Some PRV’s may contain provisions to prevent causing a closed system and others may not. It is beyond the inspection to verify all components in a home and as a result the operation/function of this PRV with respect to a closed system is not known.
You can add the typical have it reviewed by a Plumber language if you want and you should make this your own wording as this is an example.
That’s another funny situation. I have not found any of these valves that are rated for installation below grade unless it is in a sealed pit or has full drainage which it never is installed that way.
This was all very helpful. Great info and great advice. Answered all my questions.
My first time on the forum and I will be back soon! Thanks all!
I should have been more specific and said many times they are installed in a sealed pit in the yard with the utility shut-off and the meter. 
Maryland only recently began requiring expansion tanks. I replaced my WH a couple of years ago and while an expansion tank is now required it never was before. The point I’m making is that many homes I see have older plumbing with no pressure valves in the county line and no expansion tanks. I don’t call them out unless it is a new install.
Note: My house does not have any pressure or backflow valves in he supply line so I only have an expansion tank because the new county code makes no distinction (new WH). WH around here get county inspection so they don’t let anyone slide. You should call your local municipality to determine what THEY require.
WOW you actually see them in sealed pits? Here they just use a plastic valve box shell around it with a plastic top. If the valve wasn’t originally half buried in soil then over the years it becomes covered over with soil. Since these are typically placed against the house, in a flower bed, they are constantly flooded either from rain or the irrigation system.