Difference between a Belfast and Butler sink?

A Belfast sink and a Butler sink are both types of large, deep fireclay sinks with a single bowl. They are known for their durability and timeless look.  

The Belfast sink, which originated in Belfast, Northern Ireland in the late 1800s, was originally designed for use in natural spring water sources and features an overflow to prevent water from draining away too quickly. The Butler sink has a similar origin, it was designed for use in working kitchens of that era, to withstand heavy usage and made of cast iron.  Today, the names are interchangeable, with a Belfast sink typically having an overflow hole and a Butler sink without one.

Another difference between the two is in their design: A Belfast sink has a plain and simple design, while a Butler sink, also known as a farmhouse sink, has more decorative features and a more traditional look, specifically a fluted front which gives it a unique appearance.