Gurgling shower waste- Any ideas?

[longdogs]

Hi

Customer said she was hearing a gurgling noise every time the loo was flushed. This is in an upstairs bathroom with toilet/shower and basin.

After a quick investigation I found that the sound was coming from the shower trap every time the loo was flushed - it sounded like an open ended waste pipe. I filled the shower trap to the top and flushed the loo and the noise stopped - only to come back after about 5 minutes.

As far as I can see there are no leaks from the shower trap and can't see why it would be due to syphonage as the bathroom has been fine for the past 3 years.

Any ideas would be appreciated

Cheers!

 

[Jasonb]

Hair down the trap acting as a wick and drawing the water out of the trap.

J

 

[longdogs]

thanks jasonb, do you think that it would drain within 5 minutes though?

 

[Youllneverguess]

Apparently so.

 

[Nige F]

and shower traps have really shallow water seals

 

[cantaloup63]

A trap full of hair won't have so much water in it to be "removed" in order that the seal breaks.

 

[Youllneverguess]

Not mentioning of course potential syphonage from the WC flush.

 

[TicklyT]

How is the soil stack vented? Open vent or AAAV?

Any birds nests in the top of the stack?

Any jammed AAAVs?

Even when working correctly, an AAAV will do nothing for positive pressure in the stack, that will just find it's way out through the weakest seal. If it can't dissipate along the drain run it will bubble up through the shallowest water trap.

It takes a negative pressure differential to open an AAAV. If the differential is larger than the depth of water in a trap will support, it will draw the trap instead of opening the AAAV.