Connecting drains at multiple levels?

[Alan Ambrose]

Hi, I’ve a 300mm culvert pipe at about -1.5m invert level that I want to drain a bunch of stuff too. I put in a big inspection chamber which has 160mm connectors at 90 degrees. I’ve new 100mm perf pipe land drains to put in, which I was going to put about 250mm down; rainwater drainage from gutters about the same level; drains at the bottom of the raft foundation about 900m down; PTP outflow maybe at 400mm (EA has approved this). The culvert is a bit silty and I was going to put in a silt trap to avoid exacerbating the situation.

 

2 questions: (1) how do I connect in at multiple levels? And (2), should the PTP outflow miss the silt trap?

[Temp]

For long drops you use a "backdrop pipe" (vertical section of pipe with a bend at the bottom and a bend/access at the top).

 

I might be wrong but I think  these days they have to go outside the Inspection chamber and connect into the ports at the bottom.

 

Something like..

[Alan Ambrose]

Ah, I hadn't thought of that, thanks. Key word is 'drop chamber'? Sounds a bit tricky. I also came across this (below). The whole area seems sufficently complicated, that I think I might need someone (rather than me) who actually knows what they're doing .

 

[crispy_wafer]

Quick example of a backdrop to go with the example image above

 

Got two inspection chambers with inlets from the build at two levels (excuse the weed’s) drops 300mm ish for another inlet before heading to the treatment plant.

 

Hopefully it gives you a brief idea of what’s going on!  Hardest bit was sealing of the stopper pipe through the riser.  Liberal use of BT1 smeared on both sides before backfilling.

 

 

 

 

[Alan Ambrose]

Thanks for the example, it seems that once you get a tiny bit out of the ordinary and the dozen or so standard parts, it’s fabricate your own system time?

 

So, where I’ve got my big old 450mm diameter IC, and ignoring the silt requirement for the minute, I could just go into the side of it at various levels?

[crispy_wafer]

Most situations have been handled before, pavingexpert is pretty damn good on this sort of stuff.  Is it a catch pit chamber you need?

[Alan Ambrose]

I suspect so.

[Conor]

Backdrops are ott for just surface water drains. Only really used for foul and combined systems. Just adjust the fall on each pipe so they all come in at the base of the chamber. Steep falls are perfectly acceptable over short distances.

[Oz07]

Even with foul I think it's been discussed here before that since pipes are mostly pvc now the maximum gradient has been deleted from building regs? I've done a backdrop before but was a tight situation without any alternative. Used pcc risers and benched traditionally.