wrote:
On 26 July, 12:22, Michael D wrote:
It's an interceptor trap:
http://www.draindomain.com/interceptor%20traps.html
Ahhhhh - that explains it. Many thanks for the swift responses.

One other question: how should I re-attach the cap? If I just push it
back in it probably won't be a very good fit & may fall out again.
Should it be fully or partially mortared in to prevent smells getting
back through? I don't know if something more modern like mastic may
work as it would make it easy to get out.

Michael

I wouldn't bother with the cap. AIUI, the modern solution would be
straight-through with no trap at all (unless there was a special
requirement like grease-traps for restaurants). I would do my best to
clear out the trap and get everything flowing as freely as possible
though.

yes. The only downside is pongs. If these are floating up from gulleys
or plugholes, then consider trapping those individually. Or source a
rubber plug from somewhere that fits. Or modify what you have to take a
standard rodding point.