No venting on soil stack

[pertinky]

Hey guys,

I've been taking down the ceiling in the downstairs kitchen to access the existing basin/shower/bath waste run to the stack in order to relocate it. The soil pipe for the WC runs parallel to the existing waste just above it.

I've finally got an unobstructed view of the entire soil pipe running from the corner of the kitchen, up in to the kitchen extension roof space, along the external wall and through in to the upstairs bathroom

I was surprised to find a couple of things:

1. Theres no AAV. The soil pipe goes underground (furthest stack from the main drains), and theres an access manhole in the kitchen that was installed before the extension was done

The stack serves the entire upstairs bathroom, as well as the kitchen basin/dish washer. Im in the middle of splitting the rather large bathroom into ensuite + family bathroom so I have to add another basin/shower/WC to this stack

2. The hole for the 110mm pipe through the external wall is more like 300mm x 200mm and has been partially filled with a few broken bricks and ALOT of expanding foam from the inside, and nothing from the outside (solid brick wall 2 course).

How was this signed off? The work was done in 2001

 

[Hugh Jaleak]

Where and how does the stack terminate currently?

 

[pertinky]

Straight through the external wall in to the WC.

I'll get some pictures

 

[pertinky]

@Hugh Jaleak Very simple diagram..

 

[Mottie]

I have the same setup as that in my garage at work although the sink goes into the wc outlet. Been like that since I fitted it in 1985. No AAV and never had any problems.

 

[pertinky]

I have the same setup as that in my garage at work although the sink goes into the wc outlet. Been like that since I fitted it in 1985. No AAV and never had any problems.

Fair enough! I haven't noticed any problems in the few months we have been here but this would have been Installed 2001. Regards might have been different then

I also have to figure out how to add another toilet adjacent to existing WC.

My thoughts were to replace end of run with double branch at same height as existing connection (branch would be almost horizontal allowing for fall) and extend branch internally to box in and fit aav

 

[pertinky]

This is what I was planning. The double branch would need to be rotated on the vertical axis to minimise the branch outlets height internally. I cannot fit the branch externally as I wouldnt be able to get the stack to the required height to fit the AAV.

So if I extend internally, I have some "dead" space between the two toilets and stud wall which can house the extended stack, and AAV with adequate venting.

Whether or not this this compliant with regs, I dont know. I should be able to get all the required falls.

 

[Nige F]

The problem with a double branch horizontal is there will be cross flow from each WC.

 

[pertinky]

The problem with a double branch horizontal is there will be cross flow from each WC.

Ah good point! Back to the drawing board

It won't be absolutely horizontal...I think I can get away with 30 to 45 degrees

This is in internal view

 

[Nige F]

It'll only work vertical - have a look on t'net @ pictures of plastic manhole bottoms - you'll see how horizontal branches are opposite ( on drainage ) and understand . Having said that There are backflow/rodent flaps that fit into pipes. If you have absolutely no other option. Let's see what others think of the flaps.

 

[pertinky]

Is there something that's more like a Y than a T? It doesn't solve the lack of venting but would ensure no cross flow

 

[Nige F]

Have a look @ the Toolstation website for 110mm Underground Soil Drainage. you'll see different Y branches. They can be assembled "in tandem " - the underground pipe is fine indoors/in a void, but not exposed to sunlight. OR Polypipe make a 112 degree double branch.

 

[pertinky]

@Nige F maybe something like https://www.toolstation.com/shop/p46128 would do?

Replace the straight pipe through the wall with one of these and then fit a double branch to go up (for AAV) and left/right for 2nd toilet)

I know less bends the better, but I dont really see another way to get the height for AAV.

May need to turn the toilet in the ensuite by 90 degrees if the outlet protrudes that bit further and run it down the stud wall instead of along the external wall

 

[Nige F]

Yes, that's a good one - ring seal joints all round so with silicone lube it can be moved around

 

[pertinky]

@Nige F Just had another look up in the roof space...

Theres no way to run another 110mm pipe through the wall and join the horizontal run as the existing one is quite close (6-8 inches) to the rafters so anything I do needs to work around the existing connection/stack im afraid.