Rule Pumps 12 Volt DC Automatic Bilge Pumps 500 GPH - 2000 GPH feature computerized operation on the principle of impeller resistance. Float switches are not required. The pump will turn on every 2-1/2 minutes to sense for water. If water is present, the pump will sense resistance and continue to run until all the water is removed. Thereafter, it will check for water every 2-1/2 minutes. Power use in the checking mode is minimal.