Sheathing hep for burying in a chase

[Muzungo]

I need to bury some 22mm Hep in the wall, and I want to do it kosher - partly to stick to the regs, and partly to avoid thermal expansion blowing the plaster.
I'm thinking 25mm corrugated electrical conduit - but I'm afraid the internal diameter may be too small. If I slit it, presumably it would expand, defeating the object..

Any ideas ?

ta in advance

 

[Bahco]

You could use some larger trunking, or double pipe trunking if you are prepared to chase into the wall. Electrical stockists should be able to help you but I don't envy you with all that work.

 

[Muzungo]

.. what can I say ? I just want that clean, everything wall-hung and chased in look. And I'm too poor to pay someone to do it, so I'm doing everything (bar the plastering, which is cheap to pay for but expensive to fubb up).
I'm hoping the conduit I ordered will fit over the Hep... otherwise I suppose the large format tiles will help.
The current 15mm was buried in a very shallow chase, and plastered over. The plaster had (predictably) blown, but mercifully the tiles held. As I'm replacing with large format (600x300) they should help.

 

[ChrisR]

Hep do a sleeving for the purpose but it may only come in long lengths.

You could just put some 1/4" ply or summat over your trench?

 

[Muzungo]

You could just put some 1/4" ply or summat over your trench?

Nice one.

Spoke to Hep's tech people - the conduit for 22mm Hep is 30mm external diameter - that's a mother of a chase.
So we reached exactly that conclusion - slap some ply over the hep at the bottom of the chase, dab of gripfill to anchor it to the wall, and plaster over that.

For the sake of posterity - here's the expansion details : 1mm per metre, per 10 degree temperature rise. So if you turn on your hot water tap on a freezing cold day, you could be looking at 3mm per metre on the hot pipe. If the hep has nowhere to slide to (eg if its a straight run between two lengths of copper) it will "buck" and blow the plaster.