Hopefully a simple one that many have had to think through before, but what is the minimum distance between underside of waste pipe or trap (whichever is lower) and top of shower tray?

 

We have concrete planks and in most places I have made allowance for a trap to sink into the the floor and pipe routing. However, we are changing the configuration of an ensuite that just didn't previously work. Consequently, the hole I have left in the concrete is no longer of use. The horizontal run is just less than 3m, so I think that means I can use 40mm pipe which would have to fall at minimum 18mm per metre and would make for (3*18mm) + 43mm = 97mm for just the pipe. Using a trap like the one below would make for a total height to underside of tray of 58mm + 54mm = 102mm.

 

https://furniture123.co.uk/p/wirquin-90mm-slim-shower-waste-dome-waterseal-30120026

 

Does that all look correct? My screed height is 40-45mm and the tiles etc will raise the floor finish up to around 60mm. That means the underside of tray only needs to be another 42mm higher than that.

 

Looking at a suitable shower tray

The top of the kerb would then be 40 + 42 = 82mm above the top of tile. In reality this would be more like 90mm to allow some wiggle room. Does that sound typical / acceptable?

 

This may sound strange, but I have never owned a walk in shower before, so have no idea on what feels right here. Always only had a bath with a shower over.

Not ideal, but I would have to have a box channel to pass the pipe along the wall that would need to be internally 40mm above finished floor and externally around 50mm above finished floor depending on the finish on the box channel.