Mercury Displacement Industries or known better as MDI Inc. Got our start in 1975 as a small family owned business. Specializing in producing mercury relays and other mercury related products. In 1990, MDI added mercury floats to its list of manufactured products. MDI quietly became a leader for both relay and float switches. Presently, we see our growth not only with the industry best products we manufacturer, but in those other great like minded brands we started to partner with in 2008. We now are able bring you a vast array of great products covering your every need in both the electrical and wastewater industries.