Hello,

What is the best type of trap for a bath? I'm sure that I've read here
before that bottle traps are not recommended because they can clog
with hair etc. but the alternative seems to be a shallow bath trap
with 20mm seal and I thought these could be emptied easily by syphonic
effects. Is it best to have a large P-trap with access hole for
cleaning?

Is the idea of the shallow trap that it will fit between the bath and
floorboards? In my bathroom someone has cut a hole in the floorboards
to fit a larger trap. Is this a problem? Do fire regs. mean that all
floor should be boarded? If so, I've got a gap in the airing cupboard
floor too.

Why is the seal height of a trap always given in millimetres: why
don't they just say standard or shallow? Is the number of millimetres
that critical?

Thanks,
Stephen.