|Posted by More on September 10, 19100 at 20:04:08:|
|In response to Re: water backup in sink|
: when the toilet is flushed, water gurgles up in the sink. clog was suspected so drains were treated with
: liquid plumber. toilet and drains work fine. this has happened in the past but it went away.
: the basement drain has backed up twice before and the city snaked and found tree roots, but no
: flooding at this time. sink and toilet are on the main floor. whats up?
: thanks, jane
Toilet drops six gallons of water into a four inch pipe. Pipe fills with water and chokes, looking for air. Toilet drain waste vent stack has been reduced from four inch to three inch to rise to the roof. Choking four inch tries to suck air from another vent that is connected to it (the sink vent). This sucking vacuum pressure pulls on the water in the p trap of the sink and causes it to gurgle. Roto snaking and liquid plumber all pass through fine.
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