I pour about a gal of water in mine, it sits in the bottom, (not enuff for the pump to pick up) - the solids settle, and get trapped into it, helping keep the solvent clean.
It also reduces the total amount of "solvent" required
I use Kerosene in my tank and I burn with kerosene quite often so now I use the dirty stuff for burning and dump the good stuff in the tank. Smells a lot better than the Tractor Supply cleaner I was using too