Underground Drainage Design advice.

[Steve247]

Hi. I’m looking for some advice please or comments on my under slab drainage layout. 
Have search the web but couldn’t find any design layouts that were helpful. 

I’m starting my build in about 6 weeks - a single storey (bungalow) with insulated concrete raft slab (with UFH) and ICF Nudura walls. 
So I need to get this right so my SE can put it on his structural General Arrangement plan drawing and my ground worker / concrete gang are coordinated. 

I’ve marked up on the attached layout my main sewer (in purple) and suggested under slab drainage in blue.

The garage and workshop might be converted to a 4th bedroom with en-suite in the future. 
so I’m not sure if having 3 bathrooms and potentially a 4th on one 110mm diameter run is ok and would comply with bldg regs. I did add another inspection chamber at the end of the run to aid access for cleaning etc. 
SVP’s are these needed? Auto air vents behind wall hung WC’s would this suffice? 
Any comments please. 
thx 

Steve
 

[Dreadnaught]

Interesting. I am unsure about having the WCs on branches. I would be tempted to find a way to have them on the main runs. Perhaps have two main runs branching from the purple IC. Just an idea.

 

My only definite comment is that you could consider just a rodding eye at the end of the run rather than a full IC if you wanted.

 

(I am not an expert but I did design (and install) my own drainage system for my current build, which has been signed off and inspected by building control.)

[Russell griffiths]

I’m no expert on this but it’s not how I would want it, how would you clear a blockage from the main runs to the wc 

wc on main run with branches for other items. 

[Steve247]

Thanks for responses. I actually share the concerns given but if I was to do a separate run for each wc for example to the main foul drainage run I then don't have the ability to rod through from the higher level which concerns me. 

 

But what I have drawn seems a lot of items on one run hence my query. 

 

Hopefully we have  a drainage expert in here that might respond. 

[Dreadnaught]

This (in green) is the sort of thing I had in mind. All WCs on main runs.

Stick a rodding eye at the end of the long run if it exceeds the max length of a run according to BC.

You don't need to angle your runs at 45º. You can approach the IC at 90º and have a short bend right next to the IC to hit the socket (bends are allowed so long as they are right next to the IC). And note that, while bends are best avoided in general, bends of <30º are generally allowed away from the IC in long runs if they are required.

 

[Mr Punter]

No issues doing this in 110mm.  With bathrooms, you could bring up a stub stack with a dirgo instead of lots of separate connections.  If possible I prefer to have the below ground outside the footprint so you could look at having a run on the right for the future bathroom and coming across the front to the main run.

[Steve247]

OK that makes lot of sense and much better thank you.  I'll be drawing it up later tonight and shall see how it looks. 

 

Thanks for comments to all. 

 

Steve

[Dreadnaught]

On the subject of SVPs, there needs to be adequate provision for ventilation of the foul drain among you and your neighbours. That does not mean every house needs an SVP. I looked at my neighbours and spotted other SVPs so told BC that I didn't need one. BC accepted it. I will just have AAVs.