# Whole Building Traps



## jar546 (Dec 16, 2018)

If there is one thing that is a pet peeve, its whole house/building traps.  They just create a double trap, are often tapped into when located inside and just cause nothing but maintenance headaches.  They are old school and unnecessary, not to mention against the plumbing code.

Thoughts?

BTW you are looking at a restaurant with an exterior grease trap and building trap even though all fixtures inside are trapped.


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## Paul Sweet (Dec 17, 2018)

The only time they might be beneficial is on a combined storm/sanitary sewer system if you're doing work in an old downtown city area.


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## steveray (Dec 17, 2018)

Someone knows that that crazy foam is not waterproof right?


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## Rick18071 (Dec 19, 2018)

Had a utility require house traps where new sewer lines were installed where everybody had septic before. It was because the old houses might not have fixtures trapped or might have S traps.


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## Bobbi_O (Oct 15, 2019)

Can anyone tell me the reason why the building traps are not allowed in the plumbing code? Many plumbers (who prob don’t read code) still put them in, prob learned from old timers.  As a code official I am just the messenger but I’d like to explain why it’s not allowed.  Many say it helps keeps odors from sewer out of the building.  So what’s the alternative design? Vents without the U trap? Thanks


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## jar546 (Oct 16, 2019)

Bobbi_O said:


> Can anyone tell me the reason why the building traps are not allowed in the plumbing code? Many plumbers (who prob don’t read code) still put them in, prob learned from old timers.  As a code official I am just the messenger but I’d like to explain why it’s not allowed.  Many say it helps keeps odors from sewer out of the building.  So what’s the alternative design? Vents without the U trap? Thanks



With today's modern building codes, all fixtures are properly trapped and vented.  There is no need to trap an entire building these days and this would specifically violate the code that does not allow double traps.  This would essentially double trap every fixture in the building.


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## tmurray (Oct 16, 2019)

You could throw extra vents in to prevent the double trapping. I don't know why you would want to work that hard to have a whole building trap, but it would fix the double trap issue.


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