Can somebody please clarify something cocerning the above. I live in a detached property, about 20 yrs old. It has only ever had the above installed regarding bathroom (2 off) wastes. It does not have an external vent. Due to odours, I queried this over the phone with the local council building control. He informed me that AIV's were for an additional toilet (say), to save running a complete new waste but it still needed externally venting. He also mentioned the terraced house situation were vented wastes are shared every few houses. 
A plumber (who isn't looking for the work), never mentioned this when he gave the system the once over. Any advice would be greatly appreciated.
A plumber (who isn't looking for the work), never mentioned this when he gave the system the once over. Any advice would be greatly appreciated.
