We've been unsuccessfully trying to find a clamping ring drain for a "wet room" shower. We're sandwiching a heavy-duty damp proof membrane (shower pan liner) between a sloped mortar bed and need a drain (with trap -- are these called trapped floor gullies?) that will clamp in the DPM and has weep holes that allow any water trapped above the DPM in this mortar bed to also drain away. So far we've only come across Aco, but they seem to only do industrial sizes. Wedi only seems to do proprietary drains for their cement board systems. Does anyone know of suppliers in the UK or Ireland of this type of drain?