What is the recommended maximum lift during drafting?

What is the recommended maximum lift during drafting?

• A. 15 feet
• B. 20 feet
• C. 25 feet
• D. 30 feet

Answer: (B)

Drafting relies on atmospheric pressure to push water up into the pump, so the suction side must stay within a safe vertical limit to maintain prime. The pump can only pull a finite water column before the vacuum becomes too strong and air pockets enter the line, which disrupts flow. In practice, plus the friction and losses in hoses and fittings, the most reliable upper limit to avoid losing prime is twenty feet. This provides a comfortable margin below what atmospheric pressure could theoretically support and keeps the suction from going so high that cavitation or loss of prime starts to occur. Lifting water only fifteen feet stays well within safe bounds, but it isn’t stated as the maximum. Lifting twenty-five or thirty feet greatly increases the risk of losing prime and reducing flow, which is why those options are not appropriate as the maximum during drafting.

Drafting relies on atmospheric pressure to push water up into the pump, so the suction side must stay within a safe vertical limit to maintain prime. The pump can only pull a finite water column before the vacuum becomes too strong and air pockets enter the line, which disrupts flow. In practice, plus the friction and losses in hoses and fittings, the most reliable upper limit to avoid losing prime is twenty feet. This provides a comfortable margin below what atmospheric pressure could theoretically support and keeps the suction from going so high that cavitation or loss of prime starts to occur.

Lifting water only fifteen feet stays well within safe bounds, but it isn’t stated as the maximum. Lifting twenty-five or thirty feet greatly increases the risk of losing prime and reducing flow, which is why those options are not appropriate as the maximum during drafting.