Opposing wastes question

15 Mar 2012
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United Kingdom

Soil stack in main bathroom sits the other side of a stud wall to a planned en-suite. Stack has a 92.5 deg branch going off to the loo, and at 90 deg at the same level, the 43mm waste from the bath.

At the same exact point I would need to join the stack in height terms, I would like to join the waste from the en-suite shower. However, of the two stack bosses remaining at that section, I'd have an opposing waste situation - either opposing the WC (obviously bad), and the other, would be opposing the bath waste from the main bathroom. There isn't room for a manifold waste. Any suggestions on what I could do? I'll try and sketch in letters, the view from above:

-O stack

The ensuite shower would need to join from the direction of the word stack, opposing the bath waste indicated by the - but I think that's not permitted?
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You can join into the boss opposite the wc or bath waste it don't fall into what is known as the danger zone.
Thanks - Perhaps I'm misreading the regs - the boss opposite the WC must fall into the danger zone? Also for the small pipes, isn't there a 110mm danger zone?
- the boss opposite the WC must fall into the danger zone?

No because it's opposite.
If you look at where the wc enters the soil stack it don't enter straight it curves the flow downwards.

The danger zone starts at the centre line of the wc waste to 200mm downwards, so nothing can be connected with 200mm from centre line and below, not opposite.

I have a pic some where. ;)
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Ah, I think I see what you are saying. Is the same true for the small bosses? If they are opposed, I don't think there is a sweep on them, or does the built in 2.5 deg angle alleviate the problem?
Ah, excellent - so opposites are ok, it's only when you are connecting in the danger zones just below that you have a problem. That's a relief indeed. So you can use all the bosses at the same level on a section. I had it in my head that if they were directly opposing it was an issue.

Very many thanks - you have probably saved me quite a lot of work.


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