Roscoe,
As stated even if you don't plan on drinking the water it still needs to be sanitized. Although if you're always using city chlorinated tap water you are probably fine.
But really you can buy a small bottle of unscented bleach at Walmart for around a dollar fifty. Pour 2 oz (1/4 cup) for every 10 gallons of tank capacity into your fresh water fill. Then fill the tank and pump the water to each faucet, toilet, and outside shower until you smell bleach. I also make sure to let it fill the water heater.
Let it sit overnight and drain it in the morning. Drain the water heater tank. Then fill the tank with fresh water and purge out all the faucets and fill the water heater again. Then drain it all again and it's ready to go.
If it still smells like bleach just flush it one more time. It will take maybe 30 minutes of actual work time as most of the time is waiting for the tank to fill or drain.
People will caution you about not pouring bleach directly into the fresh fill pipe. I say the bottle the bleach comes in is plastic and the fill pipe and tank are plastic. Also the bleach is going to get washed down with the hose as you fill the tank. It's not going to hurt anything the few times that you actually pour bleach down the hole.
.