hj
Master Plumber
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- Cave Creek, Arizona
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vent
The vent in the newest drawing is not protecting the sink drain from aspiration when the washing machine discharge is flowing past its connection. Your earlier version with two vents was one way of doing it properly. The other way would have been to connect the washer trap to the 3", (the statement about not connecting anything below a toilet applied to conditions when the stack is used as the vent), and then running the vent to another vent, (not the sink drain). AAV's can only protect against negative pressures, but anything below a toilet or washer drain can be subjected to positive pressures if they do not have an atmospheric vent. The reason why vents and flood levels are interelated is that if the vent is too low and the drain plugs up, the vent will become a secondary drain once water in the sink rises to that level.
The vent in the newest drawing is not protecting the sink drain from aspiration when the washing machine discharge is flowing past its connection. Your earlier version with two vents was one way of doing it properly. The other way would have been to connect the washer trap to the 3", (the statement about not connecting anything below a toilet applied to conditions when the stack is used as the vent), and then running the vent to another vent, (not the sink drain). AAV's can only protect against negative pressures, but anything below a toilet or washer drain can be subjected to positive pressures if they do not have an atmospheric vent. The reason why vents and flood levels are interelated is that if the vent is too low and the drain plugs up, the vent will become a secondary drain once water in the sink rises to that level.