No venting on soil stack

[pertinky]

Just had a look at the plans again...

The foul is running the opposite way to what I had assumed so the ventilated stack is at the HEAD of the drain. The drawing has the ventilated stack (upstairs ensuite), and a stub stack (downstairs WC). I'm fairly sure that there is only the one (these are slightly outdated plans). This is all "new" pipework (circa 2000) and it runs to the existing access chamber which is now situated in the kitchen extension. These plans show the stub stack (upstairs bathroom) on the opposite end of the bathroom and connecting in the same access chamber. This isnt the case as it connects further down and obviously not accessible.

So the question is "does the ventilated stack make up for no ventilation on the stub stack?"

 

[Hugh Jaleak]

So the drain run shown to the right of the drawing, going vertically off the page is the head of the run and is vented? Assuming so, then this will suffice to ventilate the drainage system, but I'd still want an AAV as a minimum on the stack you're proposing to alter. It would likely be rare, but not impossible, both WC's were flushed simultaneously, and doing so could cause one or both to have the trap pulled. A single WC can cause an AAV to 'chatter' as it opens to allow air in behind the discharge.

There is the option of using a double 45 junction, whilst not ideal, if fitted with a slight fall, it may be enough to prevent any crossflow from the WC's, I'd be interested to know if anyone has used one in a semi horizontal plane without problems. https://www.ebay.co.uk/itm/263572712408?clk_rvr_id=1500691663904&rmvSB=true

 

[pertinky]

Yup, I double checked in the loft last night. There are open two vent pipes inside the stud walling (80mm) about 1m apart but only one is in use judging by the smell!

I'm with you on the AAV so I will try my best to find a way to install one. I'm going to pick up a few joints and some pipe today and see if theres any way I can run two pipes through the existing hole side by side, and then open them up on the other side in to two T junctions next to each other. Theres plenty of fall on the external run.

I would presume the AAV needs to be upstream of the furthest toilet as well?

 

[Hugh Jaleak]

AAV needs to be above the spillover level of the highest appliance connected to the stack, usually the basin.

 

[pertinky]

@Hugh Jaleak I have a plan, let me draw it up and see what you think.

 

[Ian H]

I've seen loads on the double ones fitted horizontally in commercial places. Suprisingly they do seem to work and the ones I have unblocked have been either due to scale build up from urinals or wipes being flushed and stuck.

If you could 30deg on one I think it would be fine. With a longer run into it, so further from the toilet, even better.

 

[pertinky]

Here we go...