multiple toilets seperate floors, one stack

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Steven765

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Situation is 1830 brownstone construction. 4" cast iron vent / stack basement to attic with 3 toilets emptying into it. Now I know the code says don't do this, each should have a seperate vent, but it's been running fine for almost 2 centuries. I just finished replacing everything with PVC as the cast iron was disintegrating. Naturally adding 2 extra 3" vents/ stacks wasn't happening so it went back the same way.

Is this just one of those areas where the code is overly cautious? Anyone have videos of testing this scenario? Would love to see this modeled in real life with clear pipe.
 

John Gayewski

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How do you know this system is functioning within the modern standards? How do you know that the system never burps some sewer gas from the fixtures depending on what is running simultaneously? My girlfriend never notices when our system doesn't function correctly but I do because I'm looking for it.
 

Tuttles Revenge

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The UPC has a provision that if the plumbing was installed to code originally then it will be allowed to be grandfathered in as long as no alterations are made. Repairs are OK.. as long as no fixture locations change. UNLESS the existing piping creates a dangerous situation.

Not sure which code you fall under or if other codes have a similar provision, which I assume they would. I would think that so long as you kept the fixtures the same as originally installed, you should be fine by the letter of the law... But as John points out, things might not be working totally ok, but they do well enough to not be noticed.

Newer toilets flush a big slug of water really fast which can cause positive pressure downslope.. where is that pressure being relieved at would be my biggest concern.
 

Steven765

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How do you know this system is functioning within the modern standards? How do you know that the system never burps some sewer gas from the fixtures depending on what is running simultaneously? My girlfriend never notices when our system doesn't function correctly but I do because I'm looking for it.
Fair point and ty for the reply. I went around with my inspection scope and watched the traps while family flushed 2 of the 3 at once to make sure it wasn't suctioning them. Yes I'm a dorky engineer who would do such things. I do see the water level move 1/8 to 1/4" in the basement floor drain trap I added, but that's it. Honestly it's less than I've seen the toilets move during a 50mph wind blowing past the vent of the house.
 

Jeff H Young

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Me Myself I have to cheat a little on meeting code occasionaly but this is beyond things Ive tested what if it gets a little stink going on are you going to open it all up and do it right? a single 1 1/2 vent to those 3 toilets would work or AAVs it woulda been pretty easy to improove on it. its probebly good enough as is just unethical for me to do I guess a homeowner DIY that dosent know better why not?
 

John Gayewski

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Fair point and ty for the reply. I went around with my inspection scope and watched the traps while family flushed 2 of the 3 at once to make sure it wasn't suctioning them. Yes I'm a dorky engineer who would do such things. I do see the water level move 1/8 to 1/4" in the basement floor drain trap I added, but that's it. Honestly it's less than I've seen the toilets move during a 50mph wind blowing past the vent of the house.
I would say if that's what you've observed, then your situation seems like it should be ok. The code (the one I'm more familiar with) prohibits positive pressure above 1"w.c. as a precaution. Your traps should be 2" so if you double the max 1" w.c. your trap would expel sewer gas. I'm order to ensure this doesn't happen the vents requirements are probably also "over engineered".

There are also provisions in the code for engineered systems that have been tested and signed off on, by design professionals. But the ahj doesn't have to approve them.
 
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