Just a small amount of baking soda for my 18 gallon tank, half a teaspoon. This will eliminate tastes that can come from the plastic, or from the fill hose that you use. You could use bleach once per year too, but it takes several rinses to get all the bleach out. I run water through the fill hose for a few minutes before I fill the tank because water can sit in the hose and transfer that particular taste to the water in the tank.
My DIY water tank has a 4" round access hatch, so I can see into all of it and actually get my arm and hand in there to clean it if I ever had to, but it has stayed nice and clean for about 4-5 years. The water lines are another source of something funky growing. My Westfalia van had this problem. I designed my truck camper so water always drains back into the tank when I turn the faucet/pump off. I made sure I had no sags in the water line that would hold water, it all drains out. When I drain the tank the water drains out of the pump as well. I also drink the water and have never had gastrointestinal madness from it.
Edited by BlueSky, 17 August 2022 - 11:27 PM.