backdrop inspection chamber

[Moonshine]

I need to get a poo pipe from the back of my new build to the front, and there is a level difference of about 3m in a 10m to get down

 

To do the level change i am going to probably have to do a couple of backdrop inspection chambers

 

Has anyone got guidance on how to build one from a standard  450 inspection chamber and 110m drainage? and also the maximum depth allowed of them?

[Dave Jones]

you can go down to 3m with a 450 chamber and reducer ring but they are not really practicable to rod at that depth. your in brick built / conc ring territory at much over 2m.

 

they are quite easy to make out of 110 pipe, see here for an example. Depth is going to be your problem.

 

 

https://www.pavingexpert.com/drain05

[Moonshine]

Thanks, i think i will do it in two back drops of about 1.5 - 1.8m each, something like this, the red circles being the back drops.

 

 

in that image what is the connector from the 110mm bend to the IC inlet?

[Conor]

Check the regs. I'm pretty sure you'll need to use a 1200mm ring for that kind of depth. We used 1200mm concrete rings and cut slot in midway up for the inlet.

 

From the NI building regs:

Edited October 27, 2021 by Conor

[Moonshine]

3 minutes ago, Conor said:

Check the regs. I'm pretty sure you'll need to use a 1200mm ring for that kind of depth.

 

Good shout, though table 11 of ADH says 450mm diameter for 1.2m deep and deeper, but with access restricted access as per @Dave Jones

 

 

[Conor]

That's for an inspection chamber tho. You're creating a backdrop manhole, which should be constructed to allow, not deter access. I'd speak to your BCO to see what is expected.

[cwr]

+1 to what Conor said.

 

And I think you'd need more than 2 backdrops. Also consider that the access pipe (top of backdrop pipe) needs to be subject to minium cover, so if that is say 300mm, plus pipe dia, a 1200mm deep chamber hardly gets you 800mm of drop.

 

Not sure if it's good practice but i didn't see a max gradient in the regs, so two chambers (need a chamber at change of gradient) 10m apart give a gradient of 1 in 3.3

[PeterW]

If you use plastic pipe they may let you drop that in one go with a slope as long as you put an IC at the top - you don’t want one immediately at the bottom and ideally you want a nice slow long radius bend at the bottom and a sharp one at the top. 
 

Use one of these at the bottom to stop any slowing down of the contents. 
 

https://www.drainagecentral.co.uk/110mm-Long-Radius-Drainage-Bend-225-Degrees-B5033-B5932
 

If you used 22.5° then you’ll get 3m drop over 8m run. 

[Gordo]

5 hours ago, Conor said:

That's for an inspection chamber tho. You're creating a backdrop manhole, which should be constructed to allow, not deter access. I'd speak to your BCO to see what is expected.

The England guidance is different to NI guidance on depths of IC. 
 

ICs are not intended for people to enter where as MHs are. That’s why they have to be larger. In England they accept ICs at greater depths with a restricted opening at top  to stop people trying to enter it. You have to use remote tools for clearing a blockage.

 

a dropped MH could have rodding access to the vertical stack so you can rod down to lower level drain.

Edited October 27, 2021 by Gordo