WHB Connection into a Bath Waste

[thetman]

I have relocated the in laws WHB to a gap in the wall between the bath and the SVP. Connected the new 32dia waste into the existing 40dia coming from the bath with a swept tee, the pipe runs from the bath at only a few degrees toward the SVP. Only problem is that when the sink runs away the water bubbles up the bath waste. Is there any easy way around this, non return valve or something. The bath has a flat looking shallow trap.

I can't access the waste pipe to cut a new connection as it runs down inside a brick built box out section.

 

[seco services]

have you fitted an anti syphon trap under basin

 

[thetman]

have you fitted an anti syphon trap under basin

No, Standard S trap

 

[seco services]

theirs your answer

 

[thetman]

theirs your answer

Thanks, Will give that a bash.