bowl, typically positioned just below the water line. It’s most commonly found in older residential toilets (particularly those manufactured before the 1990s) and in certain commercial or European models.
Visually, it creates a small “step” where waste lands before the flush cycle begins—which naturally leads to the question: Why doesn’t it just go straight down?
Why Was It Designed This Way? Two Practical Reasons
1. Odor Control (The Primary Goal)
The shelf helps maintain a deeper, more reliable water seal in the bowl. By temporarily holding waste above the main
