The Myth of the Overflow Hole
For a while there was a funky smell coming from the bathroom sink. I couldn't figure out what it was. I poured all sorts of liquids down the drain to get it to go away, but nothing worked. Then, one day, because the sink was draining slowly, I took out the plunger and plunged the bathroom sink. Gross. I know. But the worst part is all the blackish green goop that sprayed out of the OVERFLOW HOLE. That was where the stink was coming from.
"Overflow holes" DO NOT PREVENT ANYTHING - SINK OR BATHTUB - FROM OVERFLOWING. I have no idea why they are even called overflow holes. The real name for those "holes" is the trip lever housing. Their main purpose is to speed the draining process of your main drain. Without a trip lever housing, the drain would gurgle water down instead of smoothly flowing down.
From my research, there is no law that you have an overflow hole in either a sink or a bathtub, only that it is plumbed correctly if you do have one. Many of the newer fancier tubs no longer include them. Because who wants to take a bath that is slurping in and out of the nasty overflow hole?
Here is a problem with trip lever housings that has cropped up in the legal system:
The foam rubber seal on the back of the tub has a tendency to dry out and shrink slightly over a period of years. This creates a small gap where water can leak unseen and unknown into the compartment behind the tub, which creates a mold forest which then leads to lawsuits and huge re-mediation bills. A 25 year Remax realtor says leaking overflows are a real problem, especially in two story houses where it creates extensive mold damage in the walls below.
When you take a bath you have to stop the water a few inches below the overflow hole and the overflow hole is up to 4 inches below the rim of the tub. This means that your bath water will barely cover your belly when you lay down. That's no fun. Older claw foot tubs were much deeper and so the overflow hole wasn't such a situation. But when the modern alcove tub was popularized, I don't think they considered the overflow position and what it took away from enjoying your bath.
With a TUBSKY™ by your side, you can take a nice deep bath that has NO contact with an overflow hole OR a drain hole. I mean, who needs that wildcard in their bath? But your bath can still drain smoothly when you are done bathing. TUBSKY™, it's just a better way to bathe.