Combining bathroom wastes

[jezzer99]

Hi,

I am refitting my bathroom in an old terraced house which has a 2 pipe system. I have a basin waste (32mm) and bath waste (40mm). Can I combine them into a single 40mm pipe before running them through the wall to a hopper outside or must they remain separate. I'm just trying to minimise the number of holes in the wall.

Thanks

 

[kevplumb]

yes but fit anti syphon traps or go a size larger on the run

 

[wonderb0y]

yes, edit: bah you beat me to the reply

 

[jezzer99]

kevplumb,

you mean larger than 40mm on the combined section??

 

[kevplumb]

yes stops all the gurgling etc when you pull the plug and less liable to block

but you could use 42