Adding ACO drain to existing drainpipe - blocking smells

[mike2016]

After unblocking, excavating and digging out the drains yesterday I found that the rainwater from a small front extension feeds into the sewer drainage rather than the stormwater drainage line. There is no stormwater drainage at that side of the house at all! I want to add a linear drainage channel to the existing gully but want to avoid smells. The space is a bit tight and I'm trying to run the ACO the whole width of the front extension. 

 

I was going to cut in a 45 degree junction into the existing pipe as marked below but I would then need a gully to block smells escaping. It's a bit tight for a standard gully trap, I was thinking of a bottle gully. But is there a better way / combination than that here? I'd have to get the trap inlet below the ACO to do it's job then? Thanks. 

[ProDave]

Are you SURE that discharges to the foul drain?  It does not look anything like deep enough for what will be exiting that inspection chamber.

[mike2016]

Yes! We ran water down each gully to test it and checked this manhole and the next foul manhole for proof. It's a very shallow foul drain alright that these are all connected to. The is no riser below that manhole cover, it sits right above the pipe junctions below. 

 

Am thinking of replacing the top of the existing gutter gully with one that has an input pipe and take it around to the ACO. Need to dig a bit more concrete. There are some mad stories about the builders so am not surprised at this setup! Just need to protect the pipes from the whacker and paving work. Thanks! 

 

1 - Upstairs Loo

2  Downstairs Loo & sink

3 - Gutter discharge/gully

?? - Unknown, might be neighbours toilet??! 

[saveasteading]

Do you know the product 'drain trace'. Brown powder that becomes fluorescent yellow. that will show where the water goes, if you have rodding cceses downstream.

 

I wouldn't be surprised that a builder had done the easy thing.

 

Is the Aco to resolve a serious issue? where does the water go at present.

 

An easy answer might  be a catch pit, so that the rain flow is not obstructed, but the downstream connection is under water.