Thanks for your knowledgeable response SaveH2O!

Yep I think it is an Overflow Relief Gully (ORG) and it makes sense to have a water seal. Thanks very much bashworth.

Thanks for your responses.
I had assumed it was stormwater as didn't think sewerage would have a riser like that but admit I have absolutely no idea about such things!
Here's a…

I've noticed standing water at the bottom of a vertical stormwater drainage pipe beside my new home as per the photos below. If I hose water into the pipe the…