Clear Choice Spa Prep. This preparatory solution is added to the existing water in your spa and left in for 1 to 5 days depending on age and how dirty spa is. This thoroughly cleans out the spa and plumbing system to remove unwanted chemicals, bio film, metal and mineral buildup. It’s okay to use the hot tub during this process. Good for 2 water changes for small spas and those already using our products, or for 1 initial water change for large spas of first time users.