# Why is NPC code 2.5.4.1 being ignored in BC?



## iamzoner (Oct 29, 2009)

Code 2.5.4.1 states that every soil or waste stack shall terminate in a stack vent.

However, on every 4 and 5 story wood frame building that I have worked on so far during my career, every soil and waste stack picking up bathroom stacks terminates on the final floor with NO stack vent.

Every time I ask about this, I am told that a stack vent is unnecessary because the bathroom groups are each wet vented through their basin and then the basin is connected to a branch vent which continues from the top of the basin from the first floor.

Why is this build being accepted and passed by inspectors in BC?


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## iamzoner (Oct 29, 2009)

I figured it out. What I was missing is that every soil and waste stack that I see in construction is terminating in a stack vent/fixture drain/wet vent.

I was mistaken in assuming that a stack vent had to extend vertically off of the stack. There is no code stating that it has to be vertical. Therefore, the wet vent on the last bathroom group is also the vent for the stack.

Problem solved!


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## mrjasontgreek (May 21, 2014)

woah woah woah, hang on a minute!

you just got me reading a little more in detail on that section of the code... I think you were right the first time. the individual/continuous/dual/wet/whichever kind of vent serving the fixtures is NOT a stack vent, as it is not sized as a stack vent, it's sized as whatever kind of vent it is. the portion of the drainage system that it is tied into is NOT a soil-or-waste stack, it is a fixture drain or branch. A soil-or waste stack is only the vertical pipe which extends through one or more storeys, and any offset that forms part of that vertical pipe. any branches that tie into it are not considered part of the stack. SO, I never really took notice of it before, but I think you were right the first time, and there should be a stack vent extending vertically off the top of a soil-or-waste stack. I think they're misreading the code, can't blame them too much, I missed it too, and by the sounds of it so did a lot of other people.


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## iamzoner (Oct 29, 2009)

I called some educators at PVC to sort through things and they informed me that in the case of the top floor bathroom group, what I was confused as being a fixture drain/wet vent is actually also a stack vent specifically because the top of the soil and waste stack offsets and becomes the fixture drain for the bathroom group. 

So it's a soil and waste stack offset/branch. Because of this, the wet vent serving the bathroom group can also be the stack vent as long as it is sized properly according to both stack vents AND wet vents for the wet vented portion.

As for the continuous vent coming from the first floor bathroom group; all other wet vents from bathroom groups tie into it as well so it is acting as a vent stack. I am still unclear as to whether it meets all the codes to be a proper vent stack but I understand the intention.

So for clarification; when a sanitary T is used in the soil or waste stack to pick up a bathroom group on a floor, it is a branch connecting to the stack. But when it reaches the top floor, it offsets to become a soil and waste stack offset/branch. Therefore the wet vent serving the bathroom group on the top floor acts as a stack vent/fixture drain/wet vent and must be sized according to both stack vents and wet vents for the wet vented portion. And since it is always a 2 inch wet vent, it happens to also work out for the stack vent size since the stack bases never exceed 4 inch.


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## Leach713 (Nov 1, 2013)

iamzoner said:


> I called some educators at PVC to sort through things and they informed me that in the case of the top floor bathroom group, what I was confused as being a fixture drain/wet vent is actually also a stack vent specifically because the top of the soil and waste stack offsets and becomes the fixture drain for the bathroom group. So it's a soil and waste stack offset/branch. Because of this, the wet vent serving the bathroom group can also be the stack vent as long as it is sized properly according to both stack vents AND wet vents for the wet vented portion. As for the continuous vent coming from the first floor bathroom group; all other wet vents from bathroom groups tie into it as well so it is acting as a vent stack. I am still unclear as to whether it meets all the codes to be a proper vent stack but I understand the intention. So for clarification; when a sanitary T is used in the soil or waste stack to pick up a bathroom group on a floor, it is a branch connecting to the stack. But when it reaches the top floor, it offsets to become a soil and waste stack offset/branch. Therefore the wet vent serving the bathroom group on the top floor acts as a stack vent/fixture drain/wet vent and must be sized according to both stack vents and wet vents for the wet vented portion. And since it is always a 2 inch wet vent, it happens to also work out for the stack vent size since the stack bases never exceed 4 inch.



Also um duh


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## mrjasontgreek (May 21, 2014)

I see what you're saying, and I've never done it any other way, but I can see how that section if the code could be interpreted in multiple ways, and it's not like it doesn't work. But I do think when you get right down to it, based on the exact definitions in the code and most of the diagrams in the appendix, you were right the first time; we're skipping out on a proper stack vent.


Or you could be like a few of the guys at work and completely miss the definition of a stack, and say that every single pipe that passes through a story is a stack (like a basin drain in a bungalow :S)


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## mrjasontgreek (May 21, 2014)

I just had to pull off the road on my way to work. 


IF a fixture (let's say a lav for simplicity's sake) is acting like the upper end of a stack, then the fixture drain from the lav as it runs under the floor would be considered a horizontal offset, as you said. By that reasoning you wouldn't be allowed to tie in any other fixtures for 1.5 metres (5 feet). Not an easy thing to do in most installations...

Again, this is all just theory and reading the code, not saying that I've even thought to do it this way before, you just got me thinking about it


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## tim666 (Mar 11, 2014)

The stack vent, is just that, not a stack so it doesn't follow the rules for a stack. You size it as a stack vent, wet vent or continuous, whichever is largest.


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## iamzoner (Oct 29, 2009)

I was mistaken in my labeling the wet vent for the top floor bathroom group a stack vent/fixture drain/ wet vent.

The wet vented portion of the piping is simply a fixture drain/wet vent. The stack vent does not begin until the dry portion at the top of the last fixture.

So for a lav being the last fixture in the stack, its drain is still a drain and a wet vent for the bathroom group. It is not called a stack vent until the top of the fixture.


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