Laterals into soil pipe

[ladwey]

I'm building an extension where the house's existing soil pipe runs across the face of the building into a large inspection chamber with multiple inlets. Like this:

Could you tell me what best practice would be with regards to the pipes coming from the house into the soil pipe? Would it be like this:

Or like this:

My two further questions are:

- How best to ensure access (Would the first plan require rodding points at each join and can the second plan be properly accessed from the inspection chamber alone)?

- Given that the pipes will need to come from higher up than the existing soil pipe and that the distance from the house to the soil pipe is not great, how can I avoid problems stemming from the fall not being steep enough? Can I have them come to it at an appropriate fall and then join the existing soil pipe from above?

 

[Hugh Jaleak]

All runs need to be accessible in the event of a blockage, go chambers would be required. If you can get the Utility into the existing chamber that would solve that issue, depending on depth of sewer, a plastic chamber may suffice for the kitchen and bathroom connections. However, if the existing sewer at any point is shared and taking at least one other property, it is the Water Company's asset and you will need their permission to do anything with it.

They may also dictate to you the methods of connection they will accept and the materials used, so Plastic Chambers may not be permitted. To overcome the height difference where a shallow sewer needs to go down to meet a deeper sewer, the usual method would be via a 'Backdrop', which would be either immediately outside or sometimes inside a chamber. A good diagram can be found here. manhole backdrop problems (draindomain.com)

 

[ladwey]

That's a really, really helpful answer, thank you. If I've understood you rightly -- I'll take the Utility room out into the old inspection chamber (this will work fine), and then get the kitchen and bathroom out through the blockwork to join the existing soil pipe at a new inspection chamber that I'll add. The 'Backdrop' makes excellent sense.

Would it be possible to have both kitchen and bathroom entering the inspection chamber via backdrops? Or should they join at the IC in such a way that both can be rodded through the same hole?

And is there a preferred way of bringing the telescopic section of pipe through into a plastic IC? I've not seen one with a hole pre-made, so do you cut it out with a jigsaw (and if so, surely it then needs sealing?)

 

[ladwey]

Or of course the kitchen and bathroom could both get their own chamber! Although they would be very close together.

 

[Hugh Jaleak]

Sorry I haven't replied sooner, it's been one of those weeks....

To be quite honest, (and now I've had chance to look again), you could bring all 3 out into a new, shallow run along the back of the property, and make one connection via a backdrop to meet the invert level of the existing chamber. (Probably be a lot less work.)

It's only the WC that needs a direct connection to the drain, if you were to install a Chamber where the bathroom drainage exits the building to turn the corner, then the Kitchen and Utility could be served by Gullies. Bottle type gullies also offer rodding access from the gully, so could then join the main run using junctions, and avoid the need for additional chambers.

 

[ladwey]

Oh that's definitely the simplest layout, thank you. With that layout in mind I think I just one other question -- would back inlet bottle gullies be the best choice for the Kitchen and Utility? -- just for simplicity's sake, then it's one straight run from the new bathroom inspection chamber to the existing inspection chamber.

 

[Hugh Jaleak]

Can connect via the back inlets or drop the waste pipes in through the top, whichever is easiest.

 

[ladwey]

Lovely, thank you so much for all your detailed help in this thread!