Called into a local office block last week to sort out a toilet cistern not filling, they also mentioned that it ponged in the toilet - and it did.
Ground floor toilet, cistern boxed in with those large panels. Removed panel, repair was easy, ball valve full of scale wasn't letting much water in.
Cause of the smell was immediately apparent. Soil pipe had a upright section some 4' high, which had a push fit air admittance valve fitted -
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rather it didn't. Found that around 6' away on the opposite side to the cistern. It clearly hadn't fallen off, but been forced out by what must have been considerable pressure for it to have landed where it did.Easy enough to fix, but I wonder what caused it to be blown out so violently? Any ideas?