Plumbing code recommends U-shaped seats for public restrooms
If you've ever used a public toilet, you've probably wondered why the seats tend to be an open U-shape, while toilets for home use have fully closed round or oblong seats. As it turns out, the open shape is not merely an aesthetic design choice but also an elegant solution to a number of common problems.
There are several theories floating around the Internet about why public toilet seats look the way they do, all with varying levels of legitimacy. Cecil of The Straight Dope postulates that the shape prevents men from creating unsavory splatter when urinating.
Reddit user cjluthy explains the shape from a material and economic standpoint. According to this theory, "By taking a very small wedge out of an otherwise full circle, it changes the whole dynamic of the form. All of a sudden we have a U shape instead of an O. Now, both 'legs' of the U are able to (mostly) independently move. This raises the 'snap point' as the materials are now able to bend effectively and more thoroughly distribute load." In short, the U-shaped seat is presumed to be more reliable at withstanding force, which means that ultimately it will need to be replaced less frequently.
Roger Barry, managing director of Healthmatic, a U.K.-based company that designs and manages public restrooms, tells Mental Floss that the altered shaped has also deterred toilet seat theft in public restrooms, as the U-shaped seats are not universally fitting. There's also the common assumption that the design prevents the genitals from making contact with the seat.
The International Association of Plumbing and Mechanical Officials (IAPMO) mandates in their Uniform Plumbing Code that "Seats, for public use, shall be of the elongated type and either of the open front type or have an automatic seat cover dispenser." Based on the exception the code makes, it appears the U-shaped seats were created for hygiene reasons. Lynne Simnick, senior director of code development at IAPMO, informs Slate that the primary reason for the design choice caters specifically to women. With the increased length of the seat and the open panel, women are able “to wipe the perineal area after using the water closet” from front to back without making contact with the seat.