For anybody thinking about building an extension or conservatory the practice of having a man hole cover within the build is no longer allowed double sealed or not, as I found to my cost, I had a conservatory built with the manhole cover inside the build, three weeks after it was finished I got a knock at the door, the guy was from Thames water telling me my structure was not allowed for the above reasons I have had to take down part of it and go round the manhole, it was that or move the drain which was far to expensive, or take the whole thing down, I did ask if I applied for planning permission would it be approved the answer was no, I also rang Thames water and spoke to someone else it was still a no, from what I have read online all water companies say the same So check your self before you start any works, my builder thought a double sealed manhole cover would be ok, IT'S NOT!!!
Yeah.. Need building control to look at drains. Seen loads of crazy ways people have built over.. Good advise op.
You can't build over a public manhole: construction 101. What was your designer thinking of? Your builder should know better too. Your own manhole is fine to build over with the d/s cover. There are ways round the problem though. For instance if the chamber is there just for your connection then it may be possible for you to connect elsewhere thus removing the need for a chamber and allowing it to be piped through. There will be a limit to length but Thames are better than Anglian whose limit is 6m (or 6.6 after paying a fee). I think Thames allow up to 10m
My builder thought it was ok to place a double sealed drain cover as was i, untill I got a visit from Thames water, I have it in writing now as of Friday, no public or private man hole cover within the confines of the building I can only go on what their inspector has said,