Some advice/comment please. I have just fitted a wall mounted basin of "unbranded/unknown brand - from Homebase" and concerns started to arise when fitting the Grohe waste - when central inside the basin the waste "tube" was against the edge of the of the hole on the underside. Having fitted the basin it was noted that the basin didn't fully drain leaving a crescent shaped pool approx 2mm deep 40mm "front to back" , looking down onto the basin running from 4 to 8 o'clock and about 10mm from the waste at 6 o'clock increasing to 20-30mm at the "ends". Having an identical basin for the second bathroom I've been playing with a marble and a spirit level on the back (wall mounting) face and found that unless the back face is tipped back (i.e. by raising the front edge)
2-3mm in 180mm (height at back) then a marble placed at "6 o'clock" will remain in the basin. Therefore for this basin to drain it needs to mounted on a wall that is around 30mm out of true over 2.4m. There is no flat plane on the top of the basin to use as a reference.Is this sort of scenario normal and should I be inserting packing at the back of the basin to get complete drainage?
Guidance on fixing would be appreciated. I've currently fixed the basin to the wall (M10 studs) with a piece of 3/8" plasterboard as "packing" (awaiting tiles) and intended to remove the basin, tile the whole wall and then fix the basin on a bed of silicon sealant. Is this the correct procedure or should I be tiling round the basin.
Thanks Pete