My gut feeling is that Vasoline would be a safer bet than silicone lubricant; the truth is -- plumbers grade silicone lubricant is very thick, and you would be unlikely to get any in your tank if you put some on the O-rings.
If plumbers grade is too thick, you can go to a radio control hobby store, electric cars use different grades of silicone lubricant for their gear trains. I have white silicone grease in a 1 oz. tube for $3.50 ....
I would still use Vasoline though. That's what I use for the O-rings on my drinking water filter.