| 摘要 |
The disclosure is a system for increasing the reliability of systems for keeping auxiliary liquid-holding tanks filled and reliably functional. A float-operated switch cycles an electric pump to maintain the liquid level between full and nearly full, and a back-flow-preventing check valve is employed and modified (apertured and/or bypassed) to permit slow back leakage to "exercise" the system. The pump, its input to the tank, and the check valve are all located below the pump-turn-on level so that they never lose their prime. One arrangement for testing liquid-level control has a float on a lever arm that operates both the pump-motor-cycling switch and also a low-level switch to energize an alarm. The lever arm also rotates a shaft carrying an indicator dial and/or pointer. The shaft has a manually engageable knob or lever for submerging the float to test the operability of the pump, the alarm, and other parts. A second species of the liquid-level control has a float-operated and manually engageable vertical plunger for submerging the float for operating and testing a level indicator, switches for the pump and the alarm, and other parts.
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