Have you ever looked down in a public restroom and noticed that the toilet seat looks a little different from the one you have at home?
If you’ve ever wondered why public toilet seats are U-shaped while your seat at home is a continuous oval, you’re not alone.
There are a whole host of theories about public-toilet-seat design — people have really given this some thought, apparently. There’s even a long Reddit thread about it.
Maybe they’re cheaper to make since they require less material, some have guessed. Others wondered whether it’s to make the seats less comfortable so that people don’t linger. Another theory is that the U-shaped design helps prevent thieves from stealing public toilet seats.
The real reason is a lot simpler. There’s an organization called the International Association of Plumbing and Mechanical Officials that works with local governments and companies to implement plumbing and mechanical systems. The group also aims to protect the public’s health by writing a uniform plumbing code.
Many cities and states adopt this uniform code, which includes a clause that requires U-shaped toilet seats in public restrooms. There is an exception to this rule: If the toilet has an automatic seat cover dispenser, the seat doesn’t need to be U-shaped.
Here’s the exact language from the code: “Water closet seats shall be properly sized for the water closet bowl type, and shall be of smooth, non-absorbent material. Seats, for public use, shall be of the elongated type and either of the open front type or have an automatic seat cover dispenser.”
The thinking behind the U-shaped seat is that it creates a cleaner environment for women when they wipe, according to Lynne Simnick, senior director of code development for the association. With a U-shaped design, your toilet paper is less likely to touch an unhygienic seat.
She told Slate that this design also had men in mind. A U-shaped seat gets rid of an area that could be splashed with urine and reduces the chance that a man’s genitals come in contact with the seat.
Some variation of this rule applies to more than half the U.S. population, according to Simnick.
If you’re a little grossed out after reading about public toilets, you may feel like running to your own bathroom to start scrubbing immediately.
An easy way to remove toilet stains is to clean with vinegar or Borax powder. You can also prevent new stains by adding vinegar to your toilet bowl once a month.
Oh, and don’t forget your toilet brush. It needs a regularly cleaning, too.