Venting a new bathroom.

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Hi guys, I appreciate that similar questions may have been asked of this topic before but none seem to fit my circumstances.

We’re having a side and rear extension put in with a new kitchen across the back (drainage before the soil stack) and the bathroom in the corner where the extension turns and runs down the side of the house (ie After the soil stack). We are the last house at the top end of the foul water sewer so no one else runs into our property. The existing inspection chamber was where the new kitchen is so it has been picked out and brand new 4” pipe runs 8m from boundary, picks up the existing stack, carries on along the extension to a new inspection chamber out side the new bathroom.
But, for some reason, my builder decided to branch off this pipe approx 1m after the soil stack to run a separate line to the new toilet meaning that any basin, bath or shower waste will be discharged outside, into the main via a hopper but the toilet waste is separate and joins the main waste after about 3m run but is after the soil stack.

I’m worried that the system needs a vent after it and if so, I don’t know how this could be done because the toilet is on a different line from the others.
I hope this makes sense and that the existing stack will suffice for all the new drainage that will be up stream of it. Thanks.
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Existing stack should be fine for ventilation, but looking at the picture, you have at least 3 connections, coming into the main blind, with no access for cleaning should it be required. Firstly, I would be very surprised if Building control will pass that, secondly, if there is a problem, how are you going to get into the blind laterals to clear any problems? What is on the drawing?
 
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Existing stack should be fine for ventilation, but looking at the picture, you have at least 3 connections, coming into the main blind, with no access for cleaning should it be required. Firstly, I would be very surprised if Building control will pass that, secondly, if there is a problem, how are you going to get into the blind laterals to clear any problems? What is on the drawing?
Thank you for such a prompt reply. I’m glad to hear that the existing stack should suffice. To answer your concerns about the layout: the first connection (furthest away) is for rainwater. Our existing drainage had a combined foul and rainwater setup. The second branch is for kitchen waste. The diagonal branch is for the toilet. The rest of the main has been extended to approximately where I’m standing and will have an inspection chamber. The other two (rain water and kitchen) will discharge into roddable hoppers. The only branch that won’t be roddable will be the toilet branch.
 
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Ah, that makes sense then, (your terminology confused me a bit!) Common term in the drainage world is 'Gulley', if these are being fitted outside the building footprint, it overcomes the issue. Bottle Gullies offer integral rodding access to the outgoing drain, so easily accessed for maintenance and cleaning. (Hoppers are usually fitted on the top of rainwater pipes, to collect the discharge from one or more pipes. They are now banned for anything other than rainwater, hence I couldn't work out what you were trying to say!)

I'd get a rodding access fitted on the stack at floor level though, in the rare even the stack or lateral blocks, it will allow that to be cleared, without having to cut into the pipe.
 
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Ah, that makes sense then, (your terminology confused me a bit!) Common term in the drainage world is 'Gulley', if these are being fitted outside the building footprint, it overcomes the issue. Bottle Gullies offer integral rodding access to the outgoing drain, so easily accessed for maintenance and cleaning. (Hoppers are usually fitted on the top of rainwater pipes, to collect the discharge from one or more pipes. They are now banned for anything other than rainwater, hence I couldn't work out what you were trying to say!)

I'd get a rodding access fitted on the stack at floor level though, in the rare even the stack or lateral blocks, it will allow that to be cleared, without having to cut into the pipe.
Thanks again, Hugh. Apologies for the poor terminology. Yes, we have bottle gullies ready to go. I’ll request rodding access on the stack.

So it’s ok to have wastes connected after the stack? I’m struggling to understand how air will get behind the waste if the stack is in front of the waste.
 
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As Nige said. Ventilation is also needed to relive any positive pressure in the system, you're at the top of the run, the short distance beyond the stack to the other appliances is negligible.
 
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