The description tells me it is a modern plastic one (green bungs) Now IF the main through run is bunged at the top (inlet) and the live drains come into the sides - I would dig down and remove the bung and construct a rodding access away from the patio using a "New OsmaDrain rodding point ". I would live with the possibility of a blockage in one of the side connections ( sink gulley, WC, surface water gulley ) because they could be cleared towards the manhole. Also from your description it's not an adopted drain.
NigeF - you're right, it is a modern plastic one and I'll follow up your suggestion of a rodding point elsewhere, so thanks for that. I'm guessing it was installed when the previous owners extended the house 30 odd years ago. As there's no one else's waste passing through it, if it gets blocked it will get blocked by me alone (and in any event the only way to gain access in an emergency is through my house). Of course covering over it is not ideal but unless it's prohibited it becomes a matter of probability and my own inconvenience as I'm responsible for sorting any blockages.
If I choose a 'rustic' type paving as per Keith Mac's then a recessed tray would be fine, but I'm currently looking at vitrified porcelain hence why I want to keep the lines clean and simple. But as per StephenOak's comment, whether it's possible to 'loose lay' is something I still need to discover. From what I've read so far most porcelain paving needs an adhesive method but, for example, GeoCeramica have paving that is designed to be laid on a sand base with sand joints. And this would certainly be something to look into: https://www.londontile.co.uk/category/paving-support-pedestals
Thanks for everyone's input, I'll give it more thought.
So... I've heeded the advice and am now looking at recessed manhole covers... Currently I have a circular inspection chamber with a clear opening diameter of 450mm. My paving slab will be 1000 x 500. In order to avoid spoiling the joint lines I'm thinking that a made-to-measure recess tray the same size of the slab would do the trick. Does that sound feasible?
I'm looking at trays but can't quite get my head around how it works. Would the combined two rims of the outer tray and paving tray sit where the mortar would normally be or would they be too wide and the slab in the tray would have to be cut down anyway? If the IC diameter is 450 and the slab width is 500 would the tray have insufficient strength on two if its sides and if so could I request that the diameter be reduced? Thanks
no, you set the recessed cover in its frame and run joint lines through it if thats where they land.
the frame is set to match up best as possible with the grout lines which in turn will be set parallel off the longest rear house wall.
dont use anything circular and forget about gettin a custom made cover.
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