Rodding Access in Drainage Runs

[jcp]

I need to extend an existing 110mm combined sewer pipe, turning it at right angles around the corner of my house in order to pick up the inputs from a new bathroom.

Currently the sewer starts at the rainwater gulley trap at the corner of the house, then flows about 2 metres to inspection chamber (A) at the point where an existing WC drain is connected.

Ideally I would effectively replace the rainwater gulley with a new right-angle inspection chamber (B), and extend the sewer pipe upstream of the chamber to collect the new bathroom discharges. But then how should I re-connect the rainwater drain (a separate soakaway is not possible). I have seen various inspection chambers for a right-angled bend, some with additional (usually higher) inlets for extra pipes, but I cannot find any chamber where the additional inlet lies halfway round the right angle!

I could easily connect in the rainwater somewhere between the inspection chambers (A) & (B), but would this need another inspection chamber (making 3 within 2 metres) to allow rodding access? Maybe a replacement gulley with removable baffle would be sufficient for this purpose.

In a similar way, the bath and basin outlets from the new bathroom will come into the sewer between inspection chamber (B) and another new Inspection chamber (C) to which the new WC will be connected. Is it OK for these bath and basin drains to connect straight into the sewer (maybe via a boss on the pipe crown) without any provision for rodding.

I should say that Building Control have passed our plans, and the inspector made no negative comments on our somewhat uncertain drainage plans when he visited the site. He did however say the existing SVP linked to inspection chamber (A) would provide sufficient venting for the whole extended sewer.

I would be grateful for any useful thoughts or links to relevant guidance

Thanks

John

 

[Hugh Jaleak]

Assuming you plan to use plastic chambers, sit your chamber (B) at a 45° angle, and use 2x 45° bends in either end of the main channel run to turn the 90° corner. This leaves the option of the Gully for the rainwater to go into one of the side inlets. (If building your own chamber, you can fabricate whatever arrangement you like, but these are more expensive and time consuming to build, and few bother with them now on smaller diameter drainage.)

Otherwise, use a Bottle Gully for the rainwater, this provides rodding access, (unlikely it will ever be need for rainwater, but covers all eventualities), and just join that in on a junction into the main run.

Bath and basin wastes, these cannot be bossed into the underground pipe outside the building. Ground floor bathrooms can leave limited options for connecting wastes into the outgoing soil pipe from the WC, sometimes a manifold or boss pipe can be used, but if this isn't feasible, provide another gully for the wastes. Again use a Bottle gulley as per above.

 

[jcp]

Hi Hugh, and thanks for your help.

I accept that a straight chamber with 45° bends at each end is probably the way to go, but I was concerned about how easily a rod attachment would get round the bends. At my own house I do have a 90° chamber (with no lateral input) that is effectively the 45°-straight-45° combination you describe, and it does require quite a push to bend a rod/attachment through the skewed 45° inlet or exit.

Regarding gullies for the new bathroom wastes, I was hoping for a more aesthetic solution. The four wastes comprise the shower at the top end, followed by the WC, then the wash basin, and finally the bath. I was hoping to combine at least the basin and bath wastes inside the house, but that would still need 3 pipes through the wall, with gullies for the shower and the bath/basin, and with the WC going direct to the third inspection chamber (C). The WC waste will pass through the wall just above the DPC, then bend 90° downwards, and I was wondering about bossing the other drains into the vertical pipe section leading down to the long rest bend underneath - ensuring the bosses remain above the ground (a wide gravel path area). Would this be OK, or would separate gullies be better anyway - maybe reducing the risk of sucking water from the smaller waste traps?

Thanks again

John