Ground level Drain Vents

In the yard of my flat are two what I take to be air admittance valves for the drain. Very close to this is a roof level vent pipe for the soil pipe. What are these two ground level vents (Side by Side) doing and can they be removed. I ask this as one is damage and they are in the way? Forgot to say there are no man holes to see what is going on!

I think a photo might be useful. Simon.

I have one too on this Victorian house - right beside a manhole. I've a feeling it's rather more than a plain chamber underneath - but can't remember what it's called.

valves

doing

Then I suspect that you have a manhole chamber (or chambers) that has been covered over. The low level vents were to get air circulating in the drain from low level and up to the 'stench pipe' or stack that was conventionally placed at the head of a drain run. The vents usually start from an inspection chamber placed close to the property boundry.

AWEM

Very unlikely to be AAVs at the *bottom* of a stack - more likely rodding points. What shape are they? As someone else has said, any chance of a photo?

Yes, perhaps rodding points as they are at the back of the house. Not sure how to do a photo though?

seldom

Yes, perhaps rodding points as they are at the back of the house. Not sure how to do a photo though?

Upload it to a photo hosting site (Flicker , Photobucket etc) and post a link here to where it is. Compressed link from Tinyurl also would be a good idea as long links often get split across lines in newsposts

AWEM

A rodding point usually has a screw on cover which seals it. A ventilator, a grill.

Some older properties have what is called a Buchan trap (qv Google) - effectively an inline U-trap near the back of the pavement with a vertical shaft for rodding. But on the rodding shaft you'd have a cover of some sort, not a grille.

Yes, they are exactly like the vents you get to vent manholes, however there is no manhole, and the house next door is the same, unless someone has buried the manholes?