Moved rad using PEX pipe. This going to work?

[locoloic]

Hi all,
I needed to move a radiator to a different wall in the room. I needed to go through the joists, so used PEX pipe to get it in there.

All seems well, though the PEX bends a little when up to temperature. Just wanted to check there’s nothing else I should have done (maybe solder or bend pipes instead?), before I insulate and put the floorboards back. I could also fit some wood supports and clip the pipework to support it.

Photos taken when at full temperature and pressure (gravity fed system with pressure pump. ~2bar pressure when hot).

Many thanks in advance

 

[Dan Robinson]

Compression fittings under the floor?

Muppetry at its finest.

 

[dilalio]

Soldered copper all day long... and years ahead!

 

[John D v2.0]

Plastic pipe does sag when hot, it's not a problem as it's supported regularly enough.

 

[locoloic]

Any specific reason against compression? Just longevity?

Won't be hard to swap out the joints I can change over to soldered, in that case.

 

[Jackrae]

It's hard to solder plastic

 

[John D v2.0]

You can't solder plastic pipe so you'd need to change to copper if you prefer solder. I've always had trouble with compression on plastic even with the correct inserts and olives, but I'd avoid joints under the floor full stop where I've used plastic. Plastic fittings work fine on copper pipe.

 

[dilalio]

Any specific reason against compression? Just longevity?

Won't be hard to swap out the joints I can change over to soldered, in that case.

Any joint in an inaccessible location that would need costly disruption of building fabric to get at is better done in soldered copper if it cannot be done without using a joint at all. Comp fittings can weep over time... Just better to be safe than sorry... Obviously the quality of the soldered joint has to be up to par!

 

[cdbe]

As one diyer to another I think you've missed the point of using plastic pipe - potentially you need just 1 connection - to the original copper (which should be done with a push fit, not compression) with the plastic pipe bending to reach the new location. You can even go straight to the valve although a lot don't like the look but I don't mind it:

Alternatively, go up behind the skirting, reduce to 10mm and use valve stem elbows:

Largely due to lack of confidence in my soldering skills and because we're having laminate flooring everywhere I've repiped my entire house in plastic/manifolds without a single inaccessible joint.

 

[locoloic]

Cool, thanks. Yeah I'll solder the copper elbows, then.

Why push fit over compression for the PEX? To me, they seem like the least reliable type of connector.

 

[dilalio]

Well, if you stick to the same brand fittings as plastic pipe, the manufacturers of each will say that they're part of a "system" and, if installed correctly, will give many years of service and offer guarantees as such.

However, nothing has had as long a test period as soldered copper, which has been in situ in some properties for nigh on 100 years! The plastic systems rely on O rings... Will they last 5 years? Let alone 100... which is why plumbers prefer copper.

 

[locoloic]

Well this is exactly my thinking - compression fittings are at least all-metal rather than relying on a plastic O-ring, which feels like a longer-lasting connection type to me.

I'm totally convinced with the solder approach, so I'll get that done, but I'm still feeling going solder -> compression for the copper -> PEX joints is the safer bet. Happy to be convinced otherwise!

 

[Dan Robinson]

Ask yourself "why would those fittings be illegal if that was a gas pipe?" (they are by the way)

 

[John D v2.0]

Ask yourself "why would those fittings be illegal if that was a gas pipe?" (they are by the way)

Because gas molecules are much smaller than water but no gas can diffuse through solid copper, brass, and other metallic fittings. Plastic with rubber rings, not so gas tight

 

[Dan Robinson]

No