Developed in Connecticut a century ago, the anti-siphon valve is still a vital component for fuel oil handling safety.

Invented by Gerald Bohn in Danbury, Connecticut, this valve is still being used and adapted in modern applications.

The anti-siphon valve was invented in the early 1920s by Gerald Bohn, one of two brothers who founded Preferred Utilities Manufacturing in Danbury. The Bohn brothers were engineers who started the company as a fuel oil accessory business that grew into a fuel oil handling and system development company. Key to that growth was the ability to understand and anticipate the needs in the fuel oil handling market and develop solutions to meet challenges.

Gerald Bohn saw that there was a need to prevent fuel oil tanks from siphoning out all their fuel if there was ever a break in the suction line between the tank and the pump. He developed a completely mechanical valve that utilizes the head pressure between the tank fuel level and the fuel oil supply pump to the system. Based on this head pressure, a spring and plunger inside the valve would be sized as required. He called this innovation the anti-siphon valve.  

Anti-siphon valves also automatically shut off oil flow in the event of a fire, greatly reducing fire hazards. Since the 1990s they have been required by national fire prevention codes, thanks in large part to the efforts of David Bohn, Gerald’s grandson, who pushed for this expansion of the safety code. David now serves as Preferred’s president and CEO.

The anti-siphon valve, which was patented in 1929, has been one of Preferred Manufacturing’s key products for nearly a century. Even today, the company continues to utilize the valve and modify it for modern components. They most recently introduced the Low Vacuum Anti-Siphon Valve, which will open with only 2″ Hg of suction available. It is designed for application between the day tank and the generator pump.

The anti-siphon valve is just one of the vital pieces of equipment designed and patented by the Bohn brothers, many of which were utilized during World War II. The company is particularly well-known for outfitting heavy ocean liners with fuel equipment during the war, and for that reason, they have kept the image of a boat in their logo ever since.

“Having a century-long legacy is something we are incredibly proud of at Preferred,” said David Bohn. “Not many companies are so fortunate. Innovations like the anti-siphon valve are one of the biggest reasons that our customers trust us so much. We know the industry, and we’ve been leading the way for a hundred years.”