Bath & Basin Waste Q's

[RomanAbramovich]

I recently fitted a bath and basin at home, the waste from each converges at a pushfit tee in the bathroom (ie 2 into 1), with one 40mm waste pipe exiting the tee and thru the cavity wall, out to a upvc stack with a bossed connection.

A builder saw this the other day and said I should have anti siphon wastes on basin and bath and also 40mm non-return fitting in this configuration, because the same upvc stack has a toilet waste plumbed to it - is this opinion correct? or is it ok to leave as is?

 

[xdave]

The 40mm non-return valve is so that if your stack blocks you don't end up with last nights curry coming up through your bath and basin waste. It's not a pleasant thing to happen.

The anti-syphon traps are to prevent a vacuum in the pipe from emptying the other trap and leaving it open to the drains. If you emptied a full bath of water with your current setup it is probably emptying your basin trap. If you can hear gurgling at the waste that is what is causing it. The anti-syphon trap allows air to be bought in via a one-way valve to prevent the pressure building up and for a few pounds more should ideally be fitted every time.

 

[RomanAbramovich]

...to clarify, it is best practice to fit an anti-syphon trap to both the bath AND the basin, and in this scenario to introduce a 40mm non-return valve between the tee and the vented stack?

Reason I need to get this right is because the local bco wants to see 'drainage' when he comes to sign off a building notice for completion.