My concern is water getting into the mouth of the spigot and sitting there for a few weeks, then when you open the spigot your beer is going to be touching the remnants of that water as it is flowing out. If there is any bacteria growing in your water bath over the few weeks (an I now know from experience that there is, especially aecetobactor from fruitflies drowning in my swamp cooler...see the fruitfly thread) the the water that is touching the spigot is not going to be clean....That's why I sanitize and seal it, and re-sanitize after. Water will flow into any gaps it finds.
Although Even make a great point, I'm not concerned with water getting into the wort through the spigot, or into the fermenter...It's what happens when we use the spigot to get the beer out of the bucket (which is why I assume the OP is using a spigoted fermenter to begin with.)
If I were siphoning out of that bucket anyway and not planning to use the spigot, I would be less concerned with sanitization, and would probably just wrap it in a baggie or tinfoil, but not bother with the sanitizer.
When I was working on the AG in mr beer stuff, and having the mr beer in a swamp cooler, I went through that rigamorole, begause I would be using the spigot to rack out of the brown keg.
You're all good. You've got positive pressure as long as, like I said, the water level is lower than the wort level. As such, if you opened up the spigot to full while it was submerged, you'd actually get leakage OUT, until the two levels equalized.
