I have been using the following formula for years, we just do it once a year. There is a fine line between not using enough bleach to sanitize the tank and using too much bleach which may attack plastic and rubber components of your water system.
A couple of tips I have learned:
Bleed until you smell bleach at each faucet, do hot and cold water separately.
We always just drain the tank once and refill. Have never had an issue with excessive bleach odor
* CAUTION: DO NOT USE FOR GAS AND/OR FUEL STORAGE
To assure complete sanitation of your potable water system, it is
recommended that the following procedures be used. This applies if it
is a new system, one that has not been used for a period of time, or one
that may have become contaminated.
(1) Prepare a chlorine solution using one gallon of water and 1/4 cup of
Clorox or Purex household bleach (5% sodium hypochlorite solution).
With tank empty, pour chlorine solution into tank. Use one gallon of
solution for each 15 gallons of tank capacity.
(2) Complete filling of tank with fresh water. Open each faucet and drain
cock until all air has been released and entire system is bled.
(3) Allow to stand for three hours.
(4) Drain and flush with potable water (IMPORTANT)
(5) To remove excess chlorine taste or odor
which might remain,
prepare a solution of one quart vinegar to five gallons water and allow
this solution to agitate in tank for several days by vehicle motion.
(6) Drain tank and again flush with potable water (IMPORTANT)
The above recommendations conform to Section 10.8 in the A 119.2
code covering electrical
of a recreational vehicle.
the solution is approved and recommended by competent health