Storing an Old Sump or Ejector Pump for Later Use
I've never stored an ejector pump &quot;wet&quot; but if I wanted to do that, I'd store it in a 50-50 mix of distilled water and standard green automotive antifreeze. The antifreeze contains rust inhibitors. I've personally stored a large diesel engine with a cast iron block for five years after flushing and filling it with 50-50 green antifreeze, and at the end of that time the fluid came out perfectly clean. No rust at all. And the antifreeze won't hurt rubber parts like bleach would.
It might be good to run the pump for a few moments after immersing it to make sure all the air is pumped out of it.