Thats why I suggested something other than a device monitoring whether voltage or current was present. Either could be and it still may not be enough to spin the pump but you would have an indication that the thing is working. So a flow detector or something that could monitor pump shaft rotation would be much better way to determine if the pump was working or not, and given the possible complexities of pump shaft monitoring, the flow detector would be a better route as it is checking the work of the pump itself.
You could probably even take the detector a bit further and use some type of variable resistance tied to the lever to give an indication of actual flow rather than just a yes/no indication and it could be just something as simple as an LED bar graph.
