Maintaining air gap in new Atwood water heater

I've always heard the air gap in a water heater tank is what caused the valve to leak. Burp the valve and no more leak. At least, mine works that way. Once all air is purged from the tank, the valve no longer leaks.
The only time it comes back is when I sanitize the system by draining and filling a couple times with chlorinated and plain water. Then I heat up the water, see it dribble, burp the air and let it cool down, then repeat. Second time; no leaks.