Fulflo was established in 1912 in Cincinnati, Ohio, where it was one of the first manufacturers of centrifugal pumps. Fulflo recently celebrated its 100th anniversary. After World War I the company moved to nearby Blanchester, Ohio, and was incorporated in 1933 under its present name and trademark. Fulflo parts and valves are used in oil and gas refineries, are essential to the military including ships and aircraft carriers, and even provide fun for attendees on amusement roller coaster rides.

In the early ‘30s, Fulflo developed its principal product, the hydraulic bypass piston-type pressure relief valve, which was granted a patent in 1935. In 1982, Fulflo was purchased by Thomas R. Ruthman and is now part of the Ruthman Family of Companies. In 1998, Fulflo purchased a much larger building from the Acculift Company (formerly Vulcan Corporation), barely a mile down the road from its original home.

Patents for the original guided piston, direct acting relief valve were obtained in 1935, coincident with the onset of fluid power systems. The need for providing large flows without excessive bulk was later met by the pilot-valve-control relief valve which was patented in 1943. Fulflo pressure relief valves operate with all types of liquids in a full range of viscosities.