have you tried bleach?
Don't know any specifics for Sun Voyager, but I've read elsewhere about using bleach. I can't tell you the amount that you would need. I'll bet that if you do a Google search for [bleach +disinfect] you will find it.
Once you've figured out how much bleach you need for your tank size, dilute it 10x or more before pouring into the tank, then add water to fill the tank. I'd be tempted to drive around the block to mix it up. Then you would run each tap in the coach until you smell bleach. I'd let it sit for a few hours, maybe even overnight. Then I'd run each tap again for a bit, then drain the tank and rinse with water at least once, and you're good to go.
By the way, I'm thinking of purchasing a Sun Voyager 102 and am trying to find out the tank sizes. Can you help me with this?
Have you had any trouble with the construction of your coach? Many pictures that I've seen online show bulges in the sides, probably from the wall shifting, and this worries me some. Any problems here?