MDPE for ASHP flow and return?

[ProDave]

I'm in a "use up left over material" phase at the moment.

 

I have some left over 25mm mdpe water pipe.  I am thinking it would nicely do the flow and return from the plant room to the Air Source heat pump.  Any reason why not?  Would it be happy with the "hot water" mode flow temp of 45 degrees?

 

This would only be for the run from the plant room (above the garage) down through the garage, out and along the wall to the ASHP.

 

It would only be at low pressure fed from a small header tank at the highest point of the plant room.

 

Also thinking as it's slightly flexible, I probably won't need to bother with flexible sections of pipe which I would need if using say copper.

[Jeremy Harris]

MDPE has a max temperature rating of around 40 deg C, above that it will start to deform, so running the risk that the fittings may not seal well.  It's probably best to use a pipe that's rated for hot water use really, although you may possibly get away with it.  The thing that would worry me is the joints, because there is a fairly high risk that the pipe will deform inwards when warm, from the compression forces from the clamp ring.

[PeterW]

+1 to what @JSHarris said. We used to have problems on hot sunny days with black MDPE feeding water troughs so I would use 22mm Hep2O if possible.  

 

I would have thought the ASHP was a sealed system too not off a header tank..?

[ProDave]

Okay, that's that idea shelved.  Before I posted this I thought I had found something saying mdpe was okay up to 60 degrees so thought 45 might be okay.