Adding rest bend to existing drain, space is tight!

9 Sep 2013
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United Kingdom
I'm hoping I can get some advice about my drains. I'm adding a bathroom to my property and I need to fit a new soil stack next to an existing rainwater downspout. There is a driveway made of concrete slabs running along side the house and beside the drain, I took one of the 3' x 2' slabs up so I could investigate. The pictures below show the current layout of the drain - the downspout feeds into a gully trap and then connects via a clay dropshaft into a combined rainwater/foulwater sewer. The sewer branch it drops into is around 2.5/3 meters below ground level, and is shared.

Current layout

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I've drawn up a plan of what I propose to do but space is a bit tight. I'm worried that I won't have enough room to fit the rest bend, the y joint and the rubber connector in the space available (approx 1 meter between the house and the clay pipe end I'd be joining on to). Do you think there is enough space to work with? Can anyone think of an easier way of adding a rest bend and rainwater collector/trap in that space?

Proposed layout

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The only way to be sure I think is to buy the bits and assemble them onsite to see, you might be lucky!

Or go to B&Q and make up what you are trying to do in their yard with bits off the shelf and measure it.....
You might want to think about an inspection chamber rather than that Y join.

And you can save yourself a bit of space by using a bottle gulley for the rainwater- you'll need a load of extensions with it though
Save yourself a lot of grief. Use a shallow inspection chamber instead of the junction for a start. Use the depth of the chamber as a guide, and cut the clayware at that depth, fit a shallow radius bend to bring the clay back onto the (almost) horizontal plane. Then fit chamber, rest bend and gulley.
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I think the shallow inspection chamber is a good idea but I'm a bit concerned about the loading. As I said in the first post a driveway runs along the side of the house, the drain I am working on runs under this, so anything I put in will have to be able to stand up to having a car parked on or driven over it.

I've found some small diameter inspection chambers (e.g. Marley UCC7) but they seem to be rated for class A15 pedestrian areas only. Class B125 ones tend to be bigger and I don't think I have the necessary space. Would I be okay to use a Marley UCC7 in a driveway as long as I surround it with concrete and put a B125 rated cover and frame on top?
These are rated at 35 kN and marked driveway use. Yes bed it in a lump of concrete (your BCO will probably suggest that anyway).

And that 250mm diameter one at that depth will be a pest if you ever actually need to access it for rodding.

If you're really set on using the small one then all you have to do is set it so the (airtight) lid is below finished level (and concrete the base etc) then build some foundations the size of your larger lid (lintelled over the pipes obviously)- that way any load on the cover is not going to be transferred to the pipework. But if you have space for a large lid you have space for a real inspection chamber.

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