how to cap drains in concrete

[sm_jamieson]

I have to cap some drainage in concrete due to it being fairly shallow. The PVC drainage involves an inspection chamber and some length of the outlet pipes, up to a height above the outlet pipes. I was just going to surround the whole thing with concrete, making a solid block, making if pretty much indestructible and immune to any possible future leaks in the joints (they test OK now and there is no undue stress on them !). I had a look in part H, and there is this thing about using compressible board at all the joints to provide movement joints. Well I can see some advantages with this, but a lot more problems, since it is creating a weak point where if you did get a leak one day, you would be powerless to fix it. And it would be hard to ensure there was no linkage between the sections as you poured the concrete anyway. And also, what compressible board would you use here ?

In practice does anyone do this, rather than just embedding the whole lot in a solid block of concrete ?

I must admit I forget to ask the BCO about this when he came round to give me advice recently. But he did say that a band seal connection I had made was OK for the regs, but could drop when bedded, and I suggested surrounding it with concrete and he said that was a good idea to stabilize it, and he said nothing about requiring movement joints !

Thanks, Simon.

[Jim Alexander]

Trouble with that strategy is that it moves ALL the sheer stress to where the concrete ends and concrete is a lot harder than PVC. IMHO not a good idea.

Exactly how shallow?

Talked yourself into that I think. I find the BCO advice about the band seal (only) dropping curious.

Jim A

[sm_jamieson]

Yep. Regs say on exit from the concrete, use a rocker joint to protect against this problem (which I would do ).

The part that would need capping is the depth to be within the compressed MOT layer. (screed 75mm, concrete 125mm, celotex 75mm, sand

25mm, MOT 125mm). By the way, it's this depth so a required internal inspection chamber is within 600mm of the finished floor so I can use a mini access chamber. One method is to pour the slab over the drains so they effectively hang from the slab, which is a rather horrid method since you can't check anything until it is too late ! Also, since the drainage has been layed before the MOT compaction, the options are limited.

No, the BCO looked at the band seal, said can't fault you on the regs, and suggested replacing it with a PVC connection. Thing is, the band seal is providing a slight change in angle (within regs). I could have used a variable angle connector, but now the two ends are fixed, I need a slip junction. So a band seal is OK, but BCO said it may drop when bedding. I said it could be encased in concrete to make it rigid and he said, yeah that would do it !

All of this regs / BCO stuff is so much fun ! Simon.

[sm_jamieson]

I think me meant it could sag since it is bendier than the pipes.

[sm_jamieson]

Hi Jim, any more thoughts on this ?

Simon.