From the manhole of the victorian sewer I have one pipe going up the outside of the house, with a branch from the upstairs toilet, then up to the top where it breathes.

But there's another pipe going up about five feet to a grill. This smells. But what's the point of it if the sewer can breathe through the pipe at the roof?

Can I block it with cement?

Or could there be a reason for it?

George