I'm planning to take up an old garden patio and lay a new one. However there is an ugly raised drain cover in the middle. This is for inspection of the property's drain at the point where it connects to a communal drain.

open drain

The drain sits 4" above the current level of the patio, so I would like to a) modernise the look of this drain, and b) lower it so that it's flush with the new patio. Raising the patio is not an option as the current level is ~17cm below the damp proof coursing and I've read that it shouldn't be any less than 15cm below.

The drain cover measures 20"-26" (imperial because it was built in 1969). The frame (which I believe is called the crown?) measures 24"-32". The top of the crown is 4" above the patio level.

Now I seem to have two options:

  1. Remove the crown and replace with a flat manhole cover. Raise the patio level fractionally to get it flush.

  2. Remove the crown and replace with a recessed manhole cover, which will look nicer because it can be filled with slabs to match the patio. However I would need to drop the height of the drain to do this, as being recessed it would need to be based lower than the patio level.

So my question regards the process of doing this:

  • I have read that the crown should just lift off (2 man effort). Is this likely to be correct? I'm going to assume worse case and it's secured somehow - how can I safely remove it without damaging the drain (and making me unpopular with the neighbours!).

  • Presumably I can lower it by removing one of those concrete "rings" in the picture and then building it up again to a lesser height? How would I go about this? It feels a bit beyond my capability (no building experience).

  • What size manhole cover should I be looking for? Most places only seem to stock ones like these that state 18"-24" which seems too small, but that is perhaps the cover size? And then they don't state the frame size. I did find this recessed one which states size including frame and would fit, but would require lowering the drain.

My preference would be to have a nice recessed cover but I think this may be beyond my capability. I have somewhat basic DIY experience (fixing things to walls, painting and decorating, replacing toilet flushes etc - no actual building work).

  • Is this the actual picture or an approximation? – Greg Nickoloff Apr 26 '20 at 13:00
  • 3
    Depending on local rules, you might want to check with your sewer/drain provider i.e., is this considered "yours to do with as you like" or "theirs and they should be involved in and approve any modification" since if it's the latter doing the former can get unpleasant... – Ecnerwal Apr 26 '20 at 13:32
  • It sure looks like the municipalities property. – blacksmith37 Apr 26 '20 at 15:48
  • @GregNickoloff the picture is the actual drain – Owen Pauling Apr 26 '20 at 16:21
  • @Ecnerwal good point. This is in the back garden, so my property. But if there was a blockage in the communal part of the drain then that would be a job for the water board, so it could be either I guess. – Owen Pauling Apr 26 '20 at 16:22

Yes that appears to simply be set on top of a spacer which is then set on top of the buried box. You should be able to lift it off, with some effort, and also keep in mind that some adhesive or mortar might have been used to secure it.

It looks like you should be able to remove the spacer under the lid and drop the thing down a few inches to make it flush with your surface.

A local concrete product supplier may be able to provide a nicer lid but some adapting may need to be done it order to get it to fit right.

  • This is how I would approach it too, @OwenPauling, just remember don't try to move it yourself, it's way too heavy and you could hurt yourself! Get some help or some sort of mechanical advantage. – GdD Apr 26 '20 at 13:22
  • @jwh20 thanks. Just to clarify, by the spacer you mean the first of those two thick rings? The thin ledge part is included in the crown measurements. – Owen Pauling Apr 26 '20 at 16:24
  • @GdD what sort of mechanical tool would you use for this? I'm going to have to use a pneumatic breaker on some other concrete areas but I don't really want to risk wrecking the drain with it. – Owen Pauling Apr 26 '20 at 16:25
  • 1
    Dig out around the outside and you should be able to insert a shovel or spade into the crevice between the parts and pry them apart. – jwh20 Apr 26 '20 at 16:29
  • 1
    A big-ass crowbar @OwenPauling. – GdD Apr 26 '20 at 17:28

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.