Is hydrostatic testing prerequisite for tumbling a tank?

[matt t.]

Some places are a little on the crazy side where tanks are concerned and really have no common sense. They will demand that a visual is done (and payed for) when ever a tank is opened up or other similar non-sense. Unfortunately you have found one of these places. Theoretically the tumbling "may" remove some of the steel tank material, thinning the wall of the tank and changing the expansion characteristics of the tank when filling. I would call BS and take your tank somewhere else. First, I would ask them how they handle tanks that come back from hydro with rust in them (ALL steel tanks do). Do they continuously tumble the tanks and re-hydro them? Do the owners ever see their tanks again? You probably aren't interested in spending $3,000-$5,000, but buying your own compressor #1) keeps your tanks cleaner because YOU control the quality (and dryness) of air going into your tanks, #2) keeps you from having to deal with uneducated dummies with no common sense, and #3) gets you filled whatever and whenever you want. Since I started filling my own tanks 2+ years ago I haven't had a spot of rust in any of them. Before that I was having at least a few of my steel tanks tumbled yearly.