Why is there only one whirlpool in my bathtub when draining?

What?

@anniereborn The little waterspout that forms when draining a bathtub. Why is their only one and not two or none?

Because your tub only has one drain.

The whirlpool forms as a way for air to escape from the drain as it is replaced by water. It isn’t always former as water goes down a drain, but it is a naturally occurring event that is nature’s most efficient way to move air and water.

@zenvelo Their is room for more than one. Why not two?

It would be expensive to have pipes installed.

He is probably asking because his drain has multiple holes in it.

@ragingloli No just one big one. With a stopper in the middle.

Read zenvelo’s answer again. One hole—one whirlpool per hole. There is no way to introduce a second twister without disrupting the circulation of the first. The 2 MUST effectively merge because ALL of the water is moving above the drain and the single funnel is the most efficient solution to gravity’s demand that the tub be drained.

I could write on a grain of rice, what I know of whirlpools. Maybe a clog?

I believe you know more than you think. The question shows that you’ve noticed that there are never multiple funnels above a drain. You can do plenty of experiments in your tub or sink with drops of food coloring. Plug the drain. Fill the tub halfway. I hear you Northerners have water to spare up there. Have 2 different bottles of food coloring open and ready. Add a drop of one color as far from the hole as possible. Quickly add a drop of another color directly over the drain and with as little disruption as possible (a string or wire attached to it), pull the plug and watch. Then repeat the experiment, only after pulling the plug, use a stick or pencil to create a small whirlpool in the dye furthest from the drain, and watch again. If you’re quick enough, you can try to create a whirlpool rotating in the direction opposite the one around the drain and see what happens to it.