Don't you have a lot of rust in the bottom of the tank from the water? One of my friends 'inadvertently' got water in his parts cleaner and after the tank floor developed a pinhole, he drained it and the tank floor looked like the hold of the Titanic.
I have a 25 or 30 gallon drum inside of the larger drum that my washer sets on. That’s in case the smaller tank develops a leak due to rusting. I ran it for 5 years with water and solvent without any rusting.