Now, I can't speak for the OR2500, but I have a Mag 7 and an OR3500. I don't know the size of the 2500 but I do know that the 3500 is HUGE compared to my Mag 7. So you might want to take a look at the 2500 and make sure it won't be too big for your sump. The two pumps I have are going to be on two different size systems, but the amount of displacement that the 3500 would do.....it just wouldn't work in place of my Mag 7. Again, it's huge, lol. And of course I can't find measurements on the 2500.....