WC in Ensuite

[Far North]

Hi again
I think that the building regs say if the horizontal distance is 6m or more from the vent then another vent must be fitted, but i was wondering how the performance would be affected without an extra vent over 4m.

I think that i am going to put an air admitanve valve under the floor boards taking care to keep it above the possible water line of the soil pipe (i can connect it to one of the boss attachements just below the toilet - anyone see a problem with this?)

many thanks
James

 

[hi-spec plumbing heating]

Dunno where 18mm/metre comes from, the Building Regs say between 9 and 90 mm/metre, and the time-honoured McGuire's rule says 1 in 40.

In other words, there's no problem with the slope, as long as it's put in carefully. The pipe mustn't sag in the middle! The only element of naughtiness in this is that the joists were probably endowed with cross-braces "X" when installed, which get in the way. Plumbers since the year dot have just bashed them out - replacing them with horizontals, "=" fashion, is better.
I'd try to use a 4m length, so there would be no joins under the floor. Depends if you have 4m clearance outside to slide it in...

Always provide a cap somewhere for rodding something like that - outside would be OK.

you need to do some more reading before you attempt any pipework if i was you.
one min your saying 9mm /90mm then your saying 1 in 40. 1 in 40 is 25mm.
single rain water pipes can be layed at 10mm 1 in 100 not multiple rain water.