25mm vent pipe required for new Soil Stack branch?

[MAB]

My Building Inspector has suggested I will probably need a 25mm vent pipe to be added to a new branch which is to be added to my existing soil stack layout (rough sketch attached, black is existing, red is the new branch). The new wc branch is 5550mm from the existing soil stack and will serve a new ensuite and an existing bathroom wc as shown. B.Insp says the vent pipe is required to ensure water is not drawn out of the basin and shower traps when flushing the 2 wc's and that the 25mm pipe could extend vertically up into the loft area and change to 50mm at top for a Durgo valve to be fitted. Alternatively he suggested the vent pipe could run horizontally along the top of the new soil pipe branch and drop down into a nearby drain hopper. All pipe work is plastic and external on the side wall of a 1930's detached house.......I would like the solution to be as neat as possible, even though it is reasonably well hidden in a side passage way. Any thoughts or suggestions on if the 25mm vent pipe is needed or any other possible options or layouts would as always be much appreciated.

 

[Temp]

You might get away with an AAV at the end of the new branch? Would need to be indoors and accessible.

 

Another option is to run the basin wastes all the way to the stack rather than share the branch with the WC.

 

 

[Vijay]

8 hours ago, Temp said:

You might get away with an AAV at the end of the new branch? Would need to be indoors and accessible.

 

Another option is to run the basin wastes all the way to the stack rather than share the branch with the WC.

 

 

 

Something like this? https://www.studor.net/maxi-vent

[PeterW]

9 hours ago, MAB said:

My Building Inspector has suggested I will probably need a 25mm vent pipe to be added to a new branch which is to be added to my existing soil stack layout (rough sketch attached, black is existing, red is the new branch). The new wc branch is 5550mm from the existing soil stack and will serve a new ensuite and an existing bathroom wc as shown. B.Insp says the vent pipe is required to ensure water is not drawn out of the basin and shower traps when flushing the 2 wc's and that the 25mm pipe could extend vertically up into the loft area and change to 50mm at top for a Durgo valve to be fitted. Alternatively he suggested the vent pipe could run horizontally along the top of the new soil pipe branch and drop down into a nearby drain hopper. All pipe work is plastic and external on the side wall of a 1930's detached house.......I would like the solution to be as neat as possible, even though it is reasonably well hidden in a side passage way. Any thoughts or suggestions on if the 25mm vent pipe is needed or any other possible options or layouts would as always be much appreciated.

 

 

Just run all the basin pipework in 40mm and use one of these on the top of the last basin 

 

http://www.toolstation.com/shop/p54349?table=no

 

Will be fine for the run - I wouldn't start running additional vent pipes or waste runs

 

Edited April 19, 2017 by PeterW
Edited Link

[Nickfromwales]

Your BCO is being really ridiculous here IMO. The furthest WC on that run ( ensuite ) immediately runs to horizontal, therefore you'll immediately get an air-break ( water sitting low in the pipe so air can travel in the remaining gap above it ), so it's total nonsense afaic. For the ensuite basin, just fit one of these and tell him to go back into his cave.  That air admittance trap will also cover you for the ensuite shower connection so nothing needed there either. 

The ONLY time that run will see the vacuum deficit that the air admittance is there to mitigate will be when the slug of water from the flush drops vertically, eg at the main stack 'drop', and that is covered by the stack being vented to atmosphere, so I really don't see any issue here at all. 

And where the hell did he get 25mm pipework from?  32mm would be the standard and you can get a 32mm AAV. 

 

[Temp]

9 hours ago, Vijay said:

 

Something like this? https://www.studor.net/maxi-vent

 

Yes that's what I was thinking of but Nicks air admittance trap is a better suggestion. 

 

 

Edited April 19, 2017 by Temp

[MAB]

Thanks all for the help and suggestions, I like the idea of Nick's air admittance trap.......I did not know these even existed. To be fair to my BCO after 'thinking off the top of his head', he did suggest asking a professional plumber who he thought would probably have a better solution than his to add a suitable vent. He has been quite helpful on other parts of my build and seems open to alternative ways of meeting the various regs.when required, so I think he should be fine with this.

[Nickfromwales]

Strange, as the BCO usually tells the plumber what the requirements are and then leaves them to execute it, but if your guy has left you to interpret it and get a plumbers PoV then fair enough . 

BCO's down here are very helpful so good to hear yours is too.