Waste Pipe Gurgling

[John]

I have just in the process of replacing my bathroom. The bath and sink wastes join up directly below the sink before exiting through the wall. When emptying the bath the sink 'gurgles', is this syphoning? How can I stop it, I cannot put a anti syphon trap under the bath due to space restrictions. The old bath and sink used the exact same setup and this didn't happen before. The only major differences now are the bath is larger (P shaped shower bath), the bath plug is one of those spring loaded 'push to seal, push to open' jobbies and the sink is a 'pop up' plug. Both plugs before were regular plugs and chains.

Cheers

John

[John]

The problem is the water from the bath is pulling a partial vacuum as it descends down the pipe. This causes the sink waste trap to let air in, hence the gurgling. You need to fit an anti vac valve onto the pipe between the bath and sink. It doesn't have to be on the bath itself.

John

[Broadback]

My bath/shower/basin/sink does this when the grid they empty into is blocked, usually by leaves! If it empties into a grid have a look at that for blockage.

[Palindr☻me]

I think that something like a Marley Monitor anti-syphon bottle trap, fixed to the *sink*, will fix the problem. As the bath empties, it pulls air from the pipe going to the sink, creating a partial vacuum which then partially empties the sink trap and draws air into it. The anti-syphon trap will allow air to be drawn directly into the pipe, preventing the partial vacuum from forming.

But IANA plumber...

[John]

Presumably something like this then?

Can these be fitted vertically or do they have to be horizontal to stop leaks, as it would be easier to fit it on the sink down pipe?

Cheers

John

[malc]

[auctions]

Fit a HepVO valve instead of the trap - much more reliable than the anti-syphon thingys

A

[Steve Walker]

Or put a coin in the bath outlet, thus reducing the rate of flow.