Re: Alright already...I was just asking!
Posted by CEA on January 26, 2004 at 17:23:24:
In response to Re: Alright already...I was just asking!
Some of the code requirements encourage more head-scratching than others, but in general they all do have a rational basis in fact.

The prohibition about using a cleanout as a drain is mostly because (1) the cleanout fitting isn't shaped to steer the water downward like a sanitary tee does, and (2) the poor bastard who has to wade into the basement to rod the building drain expects to find a cleanout.

Wet venting (using the stack as both a vent for the urinal and a drain for higher fixtures) is complicated and not allowed in general, although there are exceptions for specific configurations like typical single-floor home bathrooms. Multi-story buildings are more complicated with separate waste and vent stacks. Think through all of the possible places where a clog can occur and the consequences of each, and the venting requirements start to make at least a little more sense.

Prohibitions on air admittance vents in some areas are a matter of new technology being accepted at different rates. Some plumbers think they're an abomination. Some think they're fine. Some think they're better than the UPC's rube goldberg approach to island sink vents.

Hope this feeds your need for rational explanations at least a little bit. If you want ten more explanations, ask ten plumbers, or ask one inspector ten times...

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