Pex in Attic

Hello. I am a student working on getting my professional inspector license in San Antonio, TX… I am about a 20% into the course work so I am by no means “qualified” to be professional inspector; I do though have quite a bit of experienced in home repair and maintenance so I have a good I idea of code and proper installation of components etc. And I am a member of this organization and I plan on utilizing all of its benefits to further my educations. Now that I am a student I take every opportunity to look at home I enter an look for deficiencies and defects. A friend of mine just purchased a home that had been “upgraded” and flipped, I am doing some minor punch list work and I took the opportunity to walk around the house and do a very informal look at some of the “upgrades”. I looked in the attic and noticed that all of the plumbing that once was in the slab had been replaced by pex and was now in the attic. San Antonio is a temperate climate and it rarely gets below freezing and I know pex is more resilient when is comes to freeze ups as the plastic tends to expand as needed. But I am concerned with the brass fittings at the 90’s and splices freezing on the odd nights when it get down to the twenties. Extra insulation, blown cellulose, had been added and the pex is running on top. So counting on the heat from the house keeping the pipe from freezing is reduced. My major concern though is, it gets very hot here. We can go for three months with 100 plus days. And I’m afraid that the water lines are going to get very hot. I am sure the attic temperatures could possibly get up into the high hundreds on a 105 degree day here. And since the composition shingles are black, the radiant heat could possibly bring the water in the pipes to boiling point.??? First, there us the possibility of scald if the water temp in the lines get above 130 degrees plus and I am concrened that the pipes themselves may not be able to with- stand the expansion of the heated water. I saw no evidence of and expansion tank. There may possibly be one on the hot water side near the hot water tank. Expansion tanks are required here if a pressure reducer was installed if the static pressure is above 80 psi. I do not know what the specs are on pex and its unions regarding heat limitations. I know plastic tubing is used in radiant floor heat, but I don’t believe it is common pex. It is a different composition and floor heat usually is on the 90 to 110 degree range. if I am not mistaken. And, typically there is an expansion tank somewhere in the floor system. So after that lengthy description- is there a potential for the pex to 1. overheat and scald, 2. overheat and burst and 3. A problem other than inconvenience if the water does in fact freeze? And lastly, is pex in the attic something the original inspector should have pointed out? I know since I’m not a licensed inspector I should not be throwing my opinions around to home owners and I have not in this case. This is more of an question for my education, but if I see confirmations of my suspicions in this forum I may have to make suggestions to my friend to have the situation checked by a licensed plumber. Thank you in advance.

Most PEX tubing will be rated for:

160 psi at 73°F
100 psi at 180°F
80 psi at 200°F

I think the chance of it getting hot enough in the attic to heat water to the scalding point or damage the fittings is slim to none.

You might ask a plumber about this. I think they will allay your concerns.

I’m in the Southern California Desert and I’ve yet to see any Pex failures related to attic/unconditioned space heat.

OK Thanks. I figured it was ok and probably fine. It just seemed odd seeing water lines in an unconditioned space It still concerns me that the cold line are in a very hot attic. If at most, when turning on cold water a person feels warm water and it is not blazing hot, I won’t bring it up. This type of retrofit must be done often, but I couldn’t find anything about it in the SOP’s. I will just chalk it up to a lack of experience regarding my concern. I just hope they never get any critters that like to chew on plastic in the attic! Thanks again.

manabloc and mini-port manifolds should not be subjected to freezing temps

freezing: in locations having a winter design temperature of 32°F (0°C) or lower, all water, soil or waste pipe and associated components shall not be installed wherever subjected to freezing temperature unless adequate provision is made to protect it from freezing by insulation or heat or both

fyi: scalding starts @ 120°F, not 130°F, see & save chart for future reports


Well, there’s a whole 'nuther concern there, and one that should have occurred to me.

Any reason we should assume that rodents would not chew on PEX lines, gents?

I guess this is going to be a good question to ask my instructor when I have actual class time next week. So far everything I have learned has been from the Dunlap Systems and Standards and from my own research and this website. I have not gotten to the code portion of my instruction; when I do, it is a lengthy course- 200 hours worth. What you have stated above sounds like the national code, can local codes over- rule national? I’m sure I will find out. And thank you for the chart.

It only occurred to me because a roof rat got into my own attic and chewed through the ac condensate line. I didn’t notice the water damage until I pulled out the dishwasher that was leaking that is located on the sam wall as the line. Not only had the rat chewed through the line in the attic but through the housing of the dishwasher! The damage to the dishwasher happened over night so I caught it before any flooding occurred, who knows how long the condensate lined had been chewed through. And of course, the damage was somewhere where the wall and roof joined and there was absolutely no access to repair it. Had to run a second line to a gable end and down. After a week of traps in the attic actually having to put up sheet metal behind the dishwasher, I was finally able to trap the little buggers. And finally found the hole they were using to get in. That is a whole other story.

The problem here is that there were exterior openings that needed to be sealed.

Yes I am aware of that.

Could you please summarise your question about PEX in the attic. My ADD set in reading your first post.
What is it you are wanting to know?

I’m now just worried about the water in the lines potentially heating to above scald level on the hot summer days when the water in the line has sat idle for 8 hours. And now wondering if it was a good idea to put water lines in an attic that could be vulnerable to damage from rodents chewing through the line. We require drip pans in attics with ac units to back up if for some reason the condensate clogs. Is it a good idea to have the potential of a water line breaking, for WHATEVER reason in the attic?

I find no problem with it being in the attic as long as it is properly insulated.
Insulating the PEX helps prevent conduction (sweating).
You are referring to possibilities. In a world of infinite possibilities, anything is possible.
I would rather have a line break in the attic than under a concrete slab.

They been running (usually) un-insulated pipes in the attics in our area forever, typically on re-pipes. PEX, CPVC, Poly back in the day, even Copper in the attics, etc. Sometimes they have been insulated, makes very little difference to the temp on a July or August afternoon.

Yes, the “cold” water is hot in the summer, very hot in fact, due to the heat of the attic.
Yes, rodents will chew absoultely eveything they step on.
Yes, sometimes things will leak.


One good thing about PEX is it can come in long rolls (100’) which would/could minimize the amount of connections.

Yes all good points. It is defiantly cheaper and easier to run replacement lines through the attic than jack hammer concrete. And easier to find leaks if they happen. And I suppose it is not much different than having a water line in a second story bathroom if a leak does occur. The owner is just going to have to get used to not putting their hand in the water stream until it has cooled. Thanks for everyone’s response. And I guess if its not a deficiency in the eyes of the authorities then just leave it alone. Lesson learned.


“authorities” opinion has little or no bearing on me or for my clients unless it favors them
i still report uninsulated piping regardless to inform & cover my assets