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Discuss PEX-AL-PEX for hot water return (manifold system) in the Fittings & Pipes area at PlumbersForums.net

(Bear with me this is my first post on here...)

We're putting in a manifold system for the H+C in the bathrooms of our new house (self-build). What are everyone's opinions on using PEX-AL-PEX pipe for our hot water return system, please? Good or bad idea? The pipe says: Tmax 95 degrees C / 10 bar / ISO 9001. There's another code, but the piece I have only has 070M, then it's cut. Do I need to check the rest of it?

It's hard to find my guidance online.
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Any chance of a pic of the pipe ?
 

EvilDrPorkChop

Gas Engineer
Advent Win
My understanding was that you couldn't use Plastic on a HW circulating return circuit and that draw offs had to be at least a meter in copper before going to plastic - however not sure on the type of pipe system you are using they may approve it.
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Yep your fine for using it for secondary returns it’s classed as mlcp
 

Stigster

Esteemed
Plumber
Thanks both. Here are some pics. It's Pipex pipe, but their website wasn't very helpful. It seems to be used for UFH a lot, but assuming that's not an indicator as that runs at lower temperatures?
As the others have said, the multi layer pipe with the aluminium layer can be used for secondary return. The reason some manufacturers state their plastic pipes cannot be used as a secondary return is something like "Continuously circulating secondary return system are 'very different' to a heating circuit as the water is constantly replenished and circulated at high temperatures" or words to that effect.

I think the problem they have is that with a constantly replenished systems you are introducing fresh oxygen into the system and then circulating it at a constant high temperature.

These metal layer pipes are quite different from ordinary plastic pipe, even barrier pipe.
 
As the others have said, the multi layer pipe with the aluminium layer can be used for secondary return. The reason some manufacturers state their plastic pipes cannot be used as a secondary return is something like "Continuously circulating secondary return system are 'very different' to a heating circuit as the water is constantly replenished and circulated at high temperatures" or words to that effect.

I think the problem they have is that with a constantly replenished systems you are introducing fresh oxygen into the system and then circulating it at a constant high temperature.

These metal layer pipes are quite different from ordinary plastic pipe, even barrier pipe.
Thanks. I can see the potential limitations there. I'm going to try again to get a response from the manufacturer.
 
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