how could this be?

Jim_64

but even the aluminum is corroded on the one, with some sort of rust-red deposit

Jim_64

how could this be?

two identical pumps installed in a boiler system on the same day; 8 months later, one is completely corroded and leaking, the other still looks new

lee_7

1 made on Thursday and other made on Friday?

Charlie from wmass

Look above the corroded pump you may find a leak. f you want to find the leak look at the floor for the puddle not the sky for the leak. Unless it is a high wind basement go plumb straight up and theres the source.