How do I fix this?

[lovejoy]

Few months ago we had the bath removed and a shower cubicle installed plumber left in the original bath trap which is only a 1 1/2" inch. (should be 3")

Result when we empty wash basin the shower trap is syphoned dry and lets the drain smell into bathroom.

We now can't get at the trap to replace it without uninstalling cubicle

Advice much appreciated

should add this was plumber's last job before he emigrated to Canada so he is out of equation.

 

[Space cat]

Can you get at the waste pipe between the shower and the basin?

 

[Hufty]

Is it basin then shower (then soil stack) or shower then basin on the waste pipe? Do the shower and the basin drain properly as far as you can tell ie no blockage?

You could try changing the basin trap for either an antivac trap or a Hepworth HepVO trap - either of these should allow air in to neutralise any vacuum that is forming.
Or as SpaceCat was hinting, if you can get at the waste pipe between the two a running trap there might be suitable.

If it comes to it, rather than uninstalling the shower consider going in from the ceiling below - it can often be easier to get a bit of ceiling reboarded and reskimmed.

 

[Space cat]

Or as SpaceCat was hinting, if you can get at the waste pipe between the two a running trap there might be suitable.

Actually, I was thinking about tapping a vent pipe into it. Two traps in the same pipe would surely create an airlock problem.

 

[lovejoy]

Uninstalling is not an option, it would mean doing the whole thing again re-tiling etc.,

Hufty it is shower then basin then soil stack

 

[Youllneverguess]

It is always an option whether you like it or not.

 

[Space cat]

rather than uninstalling the shower consider going in from the ceiling below

If there is a ceiling below, that's worthy of serious consideration. The day might come when you need access to the trap anyway.

 

[algas]

Can't you re route the basin waste to connect into the soil pipe without teeing into the shower waste?

 

[lovejoy]

From outside there is only one pipe going into the soil stack so shower and basin pipes must be connected somewhere under the bathroom floor and I can't get under the floor without un- installing the shower cubicle.

The only hope I can see is tackling this on the outside but I don't know what to do exactly

 

[Agile]

It sounds to me as if the two wastes may not be correctly drained to a nearby soil stack with an open vent.

Whilst I dont do too much of that work I would expect installing an air admittance valve could well solve the problem.

Its very common to fit 1 1/2" traps to showers, presumably because of the lack of clearance height. With a properly sized combined pipe size they rarely give any problem.

Tony

 

[lovejoy]

where does one fit an AAV where physically does it go?

 

[spraggo]

Why not TRY changing your basin trap for an anti vacuum one, as Hufty suggested