Syphoning ( I think )

[Quovadis]

Hi have a toilet upstairs and a bath downstairs that shares tge same stack pipe ... Do bathroom down stairs always seems to smell a bit drainy , so I was thinking that as the toiet and bath is used upstairs as it passes the bath down stairs it acts as a symphon and take te water out of the lower bathrooms traps ... any suggestions to stop this .. was thinking of a one of those back pressure in line valves but dont think it will suit as it will allow water from the lower bath but still allow the symphon to act as the water passes ... any ideas ?

 

[Simon F]

welcome to the forum.
it might be syphoning occurring???
this could be if the pipework had been fitted badly.
shallow bath trap?
fitted to low to the soil stack?

 

[Quovadis]

100% correct ..... what should have been during the build to stop this ( especially as the bath is so low downstairs) and any suggestions to resolve the issue ? The one idea was to attempt to put a shower trap or low level trap going to a tee with a non return valve on a small stack pipe before the main drain. the thnnking is that the bath can run as normal , but when the surge of water passes the bath pipe the symphon action would be overcome by the non return valve suckig in air and then closes after the air is equalised ? Any other suggestions welcome

kind regards

 

[Simon F]

maybe some pictures, measurements so we see what you do.
possibly a waterless trap could help, hepvo

 

[SEEN]

Hello, this is my first post but had a few instances with syphoning.

You could try HepVO [fanny trap valve] or McAlpine to a combined anti-syphon bath trap [code SM10EV].

I have fitted 1 1/2" air admittance valves where space is available.

Basin anti-vac traps are pretty cheap now. I often fit them anyway to avoid future issues if someone 'modifies' the pipework...

Good luck with getting id of the smells.