parking deck roof drains

[MarkCrane]

My customer has a large multi story parking deck. The roof drains are routed to the sanitary sewer. Near the end of the waste line a master trap is installed with a fresh air vent similar to a commercial kitchen. I have been unable to identify a code requirement for this master trap. I noted that the drains are not trapped and I assume the master trap prevents sewer gas from escaping to the parking deck. Is this simply a good idea that prevents the need for heat tracing individual traps or is there a code requirement that I am not aware of?

 

[PEDARRIN2]

I do not think it is a code issue.

It might be something a code official wants based upon his experience.

Your best bet is to contact the code authority in the area and get their input.

Sometimes drainage from garages go to the sanitary and sometimes it goes to the storm. Sometimes, some sort of freeze protection is waranted, depending on if the garage is open or if it is closed and what area it is in.

Hope that gives some direction.