As was said by others better than myself, gravity vacuum might not cost anything to run (gas or electricity), it will cost you man hours to maintain. There is no vacuum system that doesn't cost something thru the season. I've had 5 animal chews on one of my runs in about 3 weeks time. I'm just hoping I have enough spare fittings to make repairs for the whole season.

Its still a lot easier and quicker than collecting buckets.