Drain clogged- how high can water rise in drain vent pipe?

A theoretical question.


assume there is a sink with a s shaped trap and with the drain going downstairs and the drain vent pipe going out through the roof. (apprx 15 feet above). Assume there is a slow clog somewhere in the system.


1- how high can water rise into the drain vent pipe?


2- Can water rise above the level of the sink into the drain pipe without seeing any water backing up into the sink?


remember the sink is squeaky clean. The clog is beyond the the s trap....

Drain clogged- how high can water rise in drain vent pipe?
In this situation, water will never go up the vent pipe past the height of the sink. The water will just overflow the sink. If you were to shove a water hose down the sink and put a rag or something to keep the water from backing up, then it would definitely come out the vent pipe. If you want to fix the problem, I would recommend removing the trap and snaking it from under the sink.
Reply:Water will rise as high as the top of the vent on the roof provided it doesn't blow your fittings apart under the sink. The only way to get water up the vent pipe is for the drain on the sink to also be plugged. I dought the threaded jounts will not leak or come apart with that amount of "head pressure".
Reply:only to the point it can find an outlet level with its height. IF the sink is independently vented and IF the clog is past the vent connection AND you are introducing a pressure source greater than atmospheric pressure it could get higher in the vent.
Reply:Yes, it could rise above the level of that sink...but only if there is more than one plug. One would be in the line going to the drain pipe, and another would have to be in the drain pipe itself...and THEN the water would have to be added by another sink or water source above all of those. Eventually that sink would back up, as the pipe fills.





Theoretically possible, but quite unlikely.
Reply:It will fill up the sink and overflow.
Reply:Answer:


1. Water pressure is calculated at 0.443 pounds per foot. With this in view I would have to say it would be determined if the water coming into the pipe is greater or less then what the vent pipe would represent at 15 ft. / 6.5 lbs.





2. Yes





Sounds like a trick question



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