Decommissioning a manhole

30 Dec 2008
Reaction score
United Kingdom
I've got a manhole where my new kitchen is going. It's where the current kitchen drains join the main soil pipe. The kitchen plumbing is moving into the extension and I'm putting in a new manhole outside the footprint. The old manhole is now not required and will be buried under the new floor

I've had a chat with BCO and he suggested putting a half section of pipe in the bottom of the manhole to make a closed pipe. What would the method be? Mortar to hold it in place then a bit of pea shingle then fill the manhole with hardcore?
Sponsored Links
1. can you scan and post a plan of the existing and proposed drainage?

2. Abandoned drainage lines are typically filled with a semi-dry mix of 4:1. Manholes may be part -filled with rubble, and 6" to 12" topped-off with the 4:1 mix.

3. Carefully work everything out before switching the drainage, all new work must be ready, esp. if a wc is involved.

4. i dont understand your/bco proposal. Dont attempt half hearted measures, or rats will possibly find a way through.
The current gulley that feeds into the existing manhole is going. The main pipe through the manhole is staying but will be buried under the floor. A new manhole will be about 2m further downstream where the new gulley will feed in. Hope this makes sense

BCO is suggesting capping the over the invert in the manhole to effectively make it a tube.
1. Have a shufti at this site:
"inserting an IC into an existing line."
Scroll down to cutting pipe and making the connections.

2. I say the above, because you might be best advised to open the existing IC base, and drop-in a length of pipe. That way no come backs or blockages.

3. pack the abandoned line with semi-dry, as above.

4. what do you mean by a "sub-stack"? does it vent to terminate above, say a flat roof, or is it AAV?

5. I presume that the line from the utility room to the WC conn. is AAV vented, say in the utility room?

6. How is the WC discharging - at right angles?

7. before any work whatsoever takes place, take care of any roof issues above the proposition. Any guttering and RWP issues ( remember that the gulleys will now be re-located). Painting or replacing the fascia. Any pointing or window frame issues.
Sponsored Links
I'd go with suggestion 2 above, break out old chamber completely and graft a new section of pipe in its place, using proper connectors. Bodgejobs on a foul line run the risk of causing repeated blockages, you dont want it coming back to haunt you once it's buried under the new floor. :cry:

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local