Waste Pipe Siphonage - any advice Gratefully Received

[LINFIO]

We have had problems with a "whiffy smell" in the downstairs bathroom ever since we moved in to the chalet bungalow. After much thought Hubby reckons this could be due to siphonage as there is an upstairs bathroom and all the waste goes through pipes in the eaves and link into the main down pipe (my profile pic shows the back of the bungy).
Any advice/tips on how this could be fixed?
PLEASE be gentle with us! xxx

 

[Hugh Jaleak]

Anti vac traps fitted to the basin/bath/shower in downstairs bathroom should overcome any siphonage issues, but siphonage is usually manifested by 'gurgling' noises when appliances are discharged.

Also quite posssible there is a leak/broken joint somwhere on the waste or soil pipework allowing foul air to escape into the room. Investigation will depend on ease of access to the pipework.....

 

[Dan Robinson]

Could also be something like hair stuck in the trap causing a wick effect.

Wherever possible I try and use HepVo traps nowadays as they act as an air admittance valve too.