How do I add sanitizer to my fresh water tank ?

Same as above... When i sanitize my system, I just add bleach to the hose and then fill the fresh water tank. I takes 1 cup of bleach for every 40 gallons of water. After the tank is full, then run all faucets until you are assured that the bleach is through the plumbing system. Let sit for (4) hours. Then drain everything, refill with fresh water, rinse the lines, and then drain the tank a second time. That's it.