Does this drainage system look ok?

[Reejoc]

We have combined drainage and want to put a downstairs loo in and connect it to an old system at the back of the house. Currently there is a clayware gully taking kicthen sink, washing machine and condenser waste.

I've planned the underground system in the attached picture to replace this and allow for a soil connection.

1) Does it look ok and will the nanny state sign it off?
2) Am I right in thinking that the stub stack has to be at least at high as the highest point of drainage (in this case the sink) and be fitted with an air admittance valve. Obviously a lower stack such as this would be better aesthetically.

Many thanks

 

[23vc]

Do you even need the i.c. Particularly if you route the boiler condensate pipe into the stub stack ...then again it’s a better idea to put one in of course

 

[John D v2.0]

1) Does it look ok and will the nanny state sign it off?

sounds like a film! if you mean building control, you should really discuss with them if you're getting them involved. if you mean you're selling and the buyer's surveyor, then they probably won't notice unless it's obviously wrong.

2) Am I right in thinking that the stub stack has to be at least at high as the highest point of drainage (in this case the sink) and be fitted with an air admittance valve. Obviously a lower stack such as this would be better aesthetically.

The stub stack's AAV would have to be higher than the spillover level of the toilet. But you can connect toilets directly to the drain if they are low enough, so no AAV needed. You would need rodding access which your example photo shows. Obviously if the toilet is fully blocked it'd be nicer if the rodding access wasn't flooded!
Presumably there's a full stack elsewhere on the system with a vent pipe or AAV, otherwise you might have other issues.

 

[Reejoc]

Do you even need the i.c. Particularly if you route the boiler condensate pipe into the stub stack ...then again it’s a better idea to put one in of course

I think with a 90 degree bend and a connection to an old system of an uncertain course it's probably best

sounds like a film! if you mean building control, you should really discuss with them if you're getting them involved. if you mean you're selling and the buyer's surveyor, then they probably won't notice unless it's obviously wrong.

The stub stack's AAV would have to be higher than the spillover level of the toilet. But you can connect toilets directly to the drain if they are low enough, so no AAV needed. You would need rodding access which your example photo shows. Obviously if the toilet is fully blocked it'd be nicer if the rodding access wasn't flooded!
Presumably there's a full stack elsewhere on the system with a vent pipe or AAV, otherwise you might have other issues.

This is a new installation at the back of the house which will convert an old gully to an underground system so no existing vent pipe or AAV. Having read a bit more the issue of the AAV height, it seems be very controversial with some people saying they work just fine at a point lower than the sink. I think I'll aim to get it as low as possible, but higher than the toilet water level.

 

[Hugh Jaleak]

Proposal looks fine to me, the reason the 'Nanny state' gets involved is to stop Muppets putting in drainage systems that dont/wont work. Saw such a lash up earlier this week, new WC in a bungalow, connected into an external stack, with the stack discharging into a gulley... Needless to say, it keeps blocking up, occupiers (a Family with small children), loose the use of the W.C., and Ripoff Rod are quoting £900 to fix it.....

AAV needs to be above spillover level of highest appliance, (i.e. the sink), or alternatively, if the drain isn't too deep, look at connecting the WC directly to the drain, and put a bottle gulley in for the sink waste. Use an access bend coming out the wall, and it'll avoid the need for the stub stack altogether.

Yes, you do need the chamber! All parts of the system need to be accessible for rodding if required. Burying a 90° bend on a horizontal run is asking for trouble!

Chamber size, again, depends on depth of drain, 300mm chamber fine to invert depths of 600mm, any deeper and you need a 450mm dia chamber.

 

[23vc]

Sorry managed to miss the fact that it was a 90 bend so totally retract the previous comment