Hi drprwnap, try this when you go away, take a 16oz empty water bottle, drill smallest hole in bottom (wire size drill bit), put one teaspoon of diclor for each day you are gone, put cap on tight, throw into tub. I have used this system and it has carried tub for 10 days and water is clean/clear when I get home. My big test will be in feb/mar when we will be gone for 18 days???... we will see how that works.
enjoy trip!!!
john