Shower waste with concrete floor

You can have the pipes boxed in - I've used 175mm upvc coverboard for this in modern bathrooms including my own. Boxing in used to always be done in plywood / hardboard etc and it always looked crap, but I would consider this long before I contemplated digging up a concrete floor.

Where do the water pipes enter the shower cubicle?

Boxing in is a last resort - there is also a lot of resistance to raising the shower tray and forming a step up from floor level at the entrance to the shower.

The H&C supply are routed via an adjoining coats cupboard, which unfortunately has no access to drainage.

-- rbel

If you must go through the concrete, use one continuous length from shower to outside, don't have any joints buried in the concrete, also, don't forget it will have to be sloped downwards towards the exterior wall otherwise you will end up with an inaccessable clog of body fat and hair. The channel will therefore have to be deeper at the wall furthest from the shower. The pipe will be carrying both hot and cold water and will be subject to expansion and contraction, so best bet will be to wrap in fibreglass prior to cementing and tiling over to allow movement without cracking tiles

A 3 metres length of 40mm pipe will span the distance between the shower waste connection and the exterior drain or the bath waste so no joins until then. I understand that the minimum fall should be 54mm for 3 metres.

I had thought of leaving the waste pipe uncovered in the floor slab channel where it runs under the shower tray and length of the bath and just covering it in a 500mm area between the shower and the bath, which can be insulated as you suggest.

-- rbel

You'll need some drop, obviously, so the way that I'd minimise it is to fit a 32mm bend (should be plenty big enough unless you're using a super-power shower) and the HepVo trap in the straight run:

Phil, Mike and Peter, many thanks for your comments.

-- rbel