Here's a tip for anyone that has a camper with a Black water tank. Even if your camper is static and hooked to inground sewage. Drain the tank as best as possible, close the holding tank valve and add a cup of water softener disolved in 1 gallon of warm water. Pour this solution down the commode. You still want to use the normal chemicals to get the decomposition process started. What this does is make the inside of the tank slippery and reduces any buildup that can occur. It also provides a degree of deoderizing. This little trick will certainly be a big help if you ever have a problem with the tank and it needs servicing. BTW...Though, there are many brands out there, Calgon is the brand I usually use to get the job done...!