Which valve is required on aircraft nozzles to prevent siphoning?

Which valve is required on aircraft nozzles to prevent siphoning?

• A. Spring-loaded Flapper Valve
• B. Tube-type Valve
• C. Antisiphon or nondrip Check Valve
• D. Positive shut-off Valve

Answer: (C)

Backflow prevention is essential in spray systems to stop liquid from being siphoned back into the water supply or tank when pressure changes. The antisiphon or nondrip check valve is designed to allow flow toward the nozzle but close off if reverse flow or negative pressure would cause siphoning. On aircraft sprayers, this valve is required at the nozzle to ensure contaminated spray can’t be drawn back into the tank or into the aircraft’s systems, protecting water supplies and non-target areas. Other valves described don’t address backflow in the same way: a spring-loaded flapper valve isn’t the standard anti-siphon device for this purpose, and a tube-type valve or a simple positive shut-off valve doesn’t prevent siphoning when pressure fluctuates. The antisiphon valve provides reliable one-way flow protection, which is why it’s the correct choice.

Backflow prevention is essential in spray systems to stop liquid from being siphoned back into the water supply or tank when pressure changes. The antisiphon or nondrip check valve is designed to allow flow toward the nozzle but close off if reverse flow or negative pressure would cause siphoning. On aircraft sprayers, this valve is required at the nozzle to ensure contaminated spray can’t be drawn back into the tank or into the aircraft’s systems, protecting water supplies and non-target areas. Other valves described don’t address backflow in the same way: a spring-loaded flapper valve isn’t the standard anti-siphon device for this purpose, and a tube-type valve or a simple positive shut-off valve doesn’t prevent siphoning when pressure fluctuates. The antisiphon valve provides reliable one-way flow protection, which is why it’s the correct choice.