kordts said:
80 psi is way plenty for lawn irrigation systems. If the system is designed and installed properly tha's all it needs.
In the sprinkler system itself, I fully agree. But the static supply pressures often go beyond 100 psi.
If the system was designed figuring on pressure over 80 psi, then the designer was a moron. 80 psi is code all over the US.
Designers tend to use what they have, and watering restrictions can require them to get the sprinkling done within a certain time frame, so nobody likes to leave any potential flow unused. That's what makes cutting in a PRV a no-go, since the system reworking could involve time and material exceeding the cost of doing the new supply work in copper
I have installed lots of RPZ's for lawn irrigation systems where it was 50 psi.
I also do RPZ retrofitting, and often have to inform a homeowner that they have inadequate, or non-existent, backflow protection, and that I won't be able to do any repairs unless the backflow protection is brought up to code. RPZ retrofits can cost more than a homeowner with one broken sprinkler head is willing to pay.
If you are a licensed plumber, and you know the pressure is over 80, you better reccomend a PRV, if they don't want one, walk away. The lawyers will come after you if anything bad happens. Helping somebody do something against code is a lose-lose.
There are too many thousands of houses without PRVs, with pressures beyond 100 psi, for me to believe that authorities around here consider it a public safety hazard. It's bad enough when someone signs off on a home inspection where the backflow protection is missing. (they seem to spend most of their time looking for sump pumps draining into the sewer system - those they catch)
My searching for higher-pressure PEX didn't turn up any specific examples yet, but I think there are some out there, according to an NSF approvals page. Funny thing, is that there is now a higher-pressure form of the 'ordinary' polyethylene tubing, made from a new resin. Unfortunately, nearly every mention of polyethylene tubing states that it is not intended for indoor usage.