Is PEX "self insulating?"

We just had a licensed plumber complete a job for us. He ran both 3/4" and 1" Wirsbo pex for the main runs. He generally strapped the hot and cold right on top of each other, and in some cases strapped them both tightly to cast iron drains.

When I expressed concern about temperature issues, he assured me that pex is "self-insulating".

What is standard practice with pex supplies?

Thanks very much!

Your plumber is a moron. The pipes have to be 4" apart by code if I recall. Just because it's PEX don't mean that it can't look good and be put in the right way.

Thanks for the reply. I asked the question right in front of our city plumbing inspector - he seemed to think it was just fine as well. If it there is actually a code requirement about keeping them apart, I'd sure like to know.

Self insulating? no but the emissivity is lower resulting in less conduction of heat however code or not I wouldn't want any hot exchanging with cold or vice-versa.

Not sure what code you are under, but Section 308 of the VA plumbing code (2006 IPC based) says that you cannot bundle hot and cold lines together.

https://www2.iccsafe.org/states/Virginia/Plumbing/Plumbing_Frameset.html

Although PEX is better than copper for thermal insulating, bundling them together creates a co-current heat exchanger. This is enhanced when the water is flowing as the heat transfer ability from the fluid to the walls improve. It may not make much difference with PEX (when flowing) as it wouldn't take much to be "conduction limited", but the heat transfer is always going to be there. You'll be wasting energy heating water only to transfer it to the cold lines. I would separate them.

Jastori if you update your location information we might have some idea of what code you come under.
We might even cite the violation if there is one.

That said the way it was installed is not what I would consider a best practice and it probably is against the code...

He must either be a very lazy plumber, or a cheap one who does not want to buy two small hangers when one larger one will work. It is not a code requirement, but it would be a "good workmanship" item.

Thanks very much for the replies.... I am in Illinois (under the "Illinois Plumbing Code"). I'll probably end up re-running a bunch of it - it doesn't make much sense to me either to have hot / cold in contact with each other as well as the cast iron drain. It certainly looks very sloppy as well. Based on cost (and recommendations) we thought we were paying for a high-quality job.

jastori said:

When I expressed concern about temperature issues, he assured me that pex is "self-insulating".

Click to expand...

PEX isn't "self-insulating", although its thermal conductivity is much lower than that of copper or iron. Standing water will eventually freeze in PEX tubing in a sub-freezing environment, it just takes a little longer. Hot water will stay hotter as it travels from the water heater to the faucet in PEX tubing. If you want your hot water to stay hotter and cold water to stay colder, I'd recommend keeping the two supply lines separated by a few inches, and also consider putting foam insulating sleeves on the hot water line, just as you would with copper or iron lines.