I've made a mistake I think

I'm plowing through the manuals for my new Roadtrek. In a document called "Green Addendum" they discuss the sanitizing procedure:

Multiply the tank capacity in gallons by 0.13. Add this number of ounces of household bleach. (So a 40 gallon tank, add 5.2 ounces.)

Seems good to me.

Thank you all for your suggestions. I really appreciate the quick responses. BTW the water is not well water.

We're at crosspurposes here regarding bleach.
OP wants to put a bit of bleach in his stored water barrels. That doesn't take much.
But now he needs to disinfect the whole system, tank, heater, and lines. That takes a bigger amount, then flush it and discard.

Well water, number one issue, if it doesn't have chlorine in it will go bad in a couple of weeks. Flush the system and bleach it, then reload with fresh water. If you have to use well water dump it when you leave, don't leave it in your tank.

I don't know if you are close to Yellowstone... Strange things have been happening in Yellowstone during the past few years. Many of the geyers have changed and some of the geology is changing as well.

If you're in a geologically unstable area or an area where fracking is being used to coax oil out of the ground....Perhaps your water source has been mixing with a mineral water source.

IMHO, more than 1/4 cup of bleach in your tank is way overkill. I have had my unit in the USNF for over two months at a time with no problem. You must have some sulfur in your supply water to make it stink. I don't know where you are in WY, but I would drain the tank. Take the anode plug out and soak it in a hot baking soda mixture, then put it back in. The only reason your anode may stink or make things stink is if you have sulfur or other obnoxious minerals in there. I would hitch up the trailer and drag it out to some place to find a fresh water supply, preferably spring water, without sulfur, even if you have to pay some rancher $10-$20 for the water. There I would fill and add the bleach and then flush after a reasonable time. Then reflush a time or two more, then refill.
I don't think you can haul enough water to fix the problem.

You may want to do some research regarding hydrogen peroxide. H2O2.

Here is a starting point:

http://greenopedia.com/hydrogen-peroxide-bleach-alternative/

We did that....and all the above advice is good.

I'll bet you the water you put in is from a well......ours is. No chlorine or treatment to begin with. 2oldman - that may be why you didn't have the problem. We live in Central Oregon and the heat in the summer, combined with well water over a period of time is GAGGY! Dirty diaper pail is exactly how it smelled.

I can't remember how many gallons our tank held......we put a GALLON in and flushed it thru, then another 1/2 gallon to let it set for about 2 hours. After that, the smell was gone. :)

Drain yes, but, collect a sample and see if there's any obvious problem. I've left water in my tank for months, and it's never stunk, at all.

You can also use an ounce or two of hydrogen peroxide to completely KILL the bleach.