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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.
 
New Uponor Feb 2020 price guide shows a new Seamless Aluminium Composite pipe, next generation Pex-Al-Pex, 'Stronger and allows the pipe to be bent in a much tighter radius'.
 
Thanks both. Food for thought. Will speak to my plumber (who's concerned about whether it'll work, but hasn't seen it yet) and my builder - who has used it previously but...isn't a plumber!
 

Chalked

Esteemed
Plumber
Gas Engineer
Have you checked with the manufacturer if it can be used on potable water?
we get 500m coils of a very similar pipe to that, from Wunda floor. But it’s only been certified for use on closed heating circuits. That’s not to say it won’t work or leak. It means the company hasn’t put it through the testing process, needed to make it wras approved.
if it isn't, you could invalidation your insurance, if there was a problem and a claim.
 
Have you checked with the manufacturer if it can be used on potable water?
we get 500m coils of a very similar pipe to that, from Wunda floor. But it’s only been certified for use on closed heating circuits. That’s not to say it won’t work or leak. It means the company hasn’t put it through the testing process, needed to make it wras approved.
if it isn't, you could invalidation your insurance, if there was a problem and a claim.
Thank you, that's a really good tip. At the moment, I can't get any response from the company (based in Spain - Pipex). I'm going to try calling them, but I thought email would be the best way, given the potential language barrier.
 

Uheat – Jake

Official Sponsor
Thank you, that's a really good tip. At the moment, I can't get any response from the company (based in Spain - Pipex). I'm going to try calling them, but I thought email would be the best way, given the potential language barrier.
If you'd like a price on our pipe which is identical then feel free to give me a call.
 
When I spoke to polypipe technical about this a few years ago they told me the constant temperature was caused the inner layer to fail bog big enough bits got back to the secondary pump to jam it.
We do a fair few secondary return systems use tectite metal tube with correct insert and there demountable fittings. You need there re rounding tool but you can bend it with a machine clip only once every meter what's not to like!
 
Hi All. I thought it was only polite to round this off... I opted to go copper for the hot water loop, but poly everywhere else. It was £400 for labour and materials for the first phase. It'll probably be just a bit less for the other side of the house (two-stage build). I thought taking the risk on plastic was a false economy for a house I'll be living in for 30yrs+. I saved the money by installing all my own waste / soil pipes (above ground) and supply pipes from the manifolds, plus the cold loop. It was a piece of p*ss tbf. Really appreciate everyone's thoughts and views.
 
Hi All. I thought it was only polite to round this off... I opted to go copper for the hot water loop, but poly everywhere else. It was £400 for labour and materials for the first phase. It'll probably be just a bit less for the other side of the house (two-stage build). I thought taking the risk on plastic was a false economy for a house I'll be living in for 30yrs+. I saved the money by installing all my own waste / soil pipes (above ground) and supply pipes from the manifolds, plus the cold loop. It was a piece of p*ss tbf. Really appreciate everyone's thoughts and views.
Any pics of your install?
 

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