How do I use two tanks?

What two tanks, what type of power washer,

A hot pressure washer, may have one for gasoline and one for Diesel to heat the water.

Is it supply tanks, one for the clean water and another for soap

? I can think of a dozen possible "tanks" on pressure washers.

I have an 1800S Husky power washer with two detergent tanks. Nowhere does it indicate which one (or both) to fill with the detergent.

:confused:

If you have two detergent tanks, you may want to use one with say a degreaser, and one with soap; or one with soap , and one with wax, etc.