Water pressure on outside hose bib was 96 psi. The plumbing lines in this home are PEX. Is PEX rated for higher pressure? I read installation instructions that I believe said the pressure is acceptable to 100 psi? I saw no pressure regulator. should I recommend lowering pressure? Starting to see a lot more PEX now.
Max residential pressure by c-de is 80 psi. What the piping, fittings, and fixtures can withstand in the laboratory is irrelevant.
Agreed. Anything over 80 psi needs to be regulated - piping material does not matter.
Having said that, PEX is a very strong material and can withstand very high pressures.
So the manufacturing instructions don’t matter?
David everything is designed to a maximum pressure allowed. You need a safety margin on all plumbing fittings and pipe and even 80 PSI is considered high under most conditions. So when we are talking about 80 PSI Joe has pointed out that is as high as is allowed on water lines under home conditions.
The max is what model code allows unless the manuf. says it should be lower, which isn’t going to be the case.
Thanks for the clarification.
Temperature limitations are always noted on the print line of the PEX tubing. PEX systems are tested to and can be used with standard T and P relief valves that operate at 210” F and 150 psi.
Some components of the plumbing system, might not last with pressures above 80 psi…, thus the reason for this limit in pressures.
Ex. washing machine hoses.
…and ice maker, toilet and humidifier parts, for more. 
Thanks Larry, saved me some thinking and typing. But that is what I was getting at.
I have already lost a washer hose due to high pressure.
Not all PEX plumbing goes to this rating so you should always check by visual.
http://www.uponor-usa.com/Header/Systems/Plumbing/Homeowner/FAQs.aspx
What temperature and pressure ratings does Uponor PEX carry?
Answer
Uponor PEX carries the following hydrostatic temperature and pressure ratings:
- 200°F at 80 psi
- 180°F at 100 psi
- 120°F at 130 psi (1/2" Wirsbo AQUAPEX tubing only)
- 73.4°F at 160 psi
Wirsbo also has the Class action law suit.
http://www.audetlaw.com/index.php/case/wirsbo_uponor_pex
The maximum pressure should be 80-90 psi. I think you should recommend them a regulator.
If these laboratory specs were truly “irrelevant” the mfgr would not bother to print them on the parts. 
Recommend a regulator, there should never be a psi rating of over 80.
Yeah, I am thinking about the many supply lines throughout the home - washer, ice maker, toilet, and under sinks. I do not check the water pressured currently, but now I am thinking I will start!
About PEX - I contacted my local AHJ about PEX being used on an electric water heater - direct connect being used for supply. The AHJ said is was perfectly acceptable. The TPR was copper - albeit not installed correctly. Thanks for this post - good info.
Why? Explain this please.