Most people do not understand the black holding tank’s purpose. It is just that, a holding tank. Its function is to hold the waste until it is dumped. Once you put chemicals into your holding tank, you have now turned it into a septic tank. The black tank was never meant for this purpose. The chemicals break down the waste causing more bacteria, parasites, and can make the smell worse. Harsh cleaning chemicals can also damage the seal in the hole of the toilet that keeps odors from coming up from the black water tank