ErtelAlsop is the result of the merger of Ertel Engineering and Alsop Engineering. Ertel Engineering was founded by Frederick Ertel in 1932 in New York City. He originally manufactured and sold depth filter media for the pharmaceutical industry. In 1938 he moved his company to Kingston, New York, about 100 miles north of Manhattan, on the Hudson River. In Kingston, Ertel expanded the business to include plate and frame filter presses, pumps, agitators, bottle fillers, and other equipment for liquid processing. In 1943 Ertel developed the first pyrogen retentive media for Bristol Labs to use in the manufacturing of penicillin for World War II. Nineteen seventy nine was the year that Ertel patented the first enclosed horizontal plate and frame filter press. The design was created in conjunction with Avon to eliminate vapors from Avon's production floor in order to improve working conditions. As usual, Ertel was willing to go the extra mile to provide a solution for its customer's application.

Alsop Engineering was founded by Samuel Alsop in 1920. The Sealed Disc Filter, Alsop's first product, was an enclosed horizontal plate filter. As a matter of fact, Alsop's first filter sheets were manufactured for them by Ertel Engineering. In the 1940's, Alsop invented an accordion shaped filter cartridge, which provided an enclosed filtration environment and much shorter changeover cycles than plate and frame filter presses. This was the first Zeta-Pak® lenticular cartridge. In addition to the cartridges, Alsop designed the corresponding filter housings. Originally vertical with removable covers, these housings have evolved to include horizontal mounting, ASME code, and sanitary designs. Alsop's product line was not limited to filters alone, it also included tanks and portable mixers. Available in both direct and gear-driven models, the mixers were unique because the same base components were used from 1/4 to 3 horsepower designs. This feature allowed the end user to maintain common parts for various sized agitators.