In the tub...?
Answers: The wet drains to the same pipe as the lower tub drain... The drain release thingy that you mentioned is the upper air vent for the tub. This water will plague the tube above the drain plug and then overflow tub... there is simply so much room in this over flow... if you want to see this contained by action... overrun the tub over the drain release slowly and then the tub hose down will just rise over the drain release... mind your Ps and Qs not to fill the tub over the top and on the floor. It is not a constant overflow protection.
The tub tub overflows that are part of the drain release lever assembly are conected to a pipe that "tee's" into the regular drain pipe. As long as it be installed properly, there shouldn't be any hose down running down inside your walls.
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