Tumbling/Hydro Test Which comes First???
“To Tumble” or “To Hydrotest?” The first judgment call after discovering a contaminated tank is one of procedural order: What comes first... tumbling or hydrotesting? There is no easy answer to this question and various experts have differing opinions. Obviously, this dilemma is largely eliminated if the dive shop can do its own hydrotesting. If the tank is first tumbled, but later fails hydrotest, the cleaning operation was wasted time and money. On the other hand, a grossly rusted and pitted tank might be visually condemned even before hydrotesting. (It is perfectly legal for a licensed hydrotest agency to visually fail a badly contaminated cylinder). To complicate matters, thick rust can trap compressible air bubbles that may throw off the hydrotest, resulting in a false failure. Thick rust can also hide serious pitting. However, it is usually a safe bet to clean a very dirty tank prior to hydrotesting. This is because very few tanks actually fail hydrotest, even if they were extremely dirty or rusty prior to cleaning. In the case of light contaminations that do not interfere with the detection of pits or cracks, it probably makes little difference in which order the procedures are done.
Traditionally, repairmen were concerned that the tumbling process itself might weaken the tank walls and so it was
believed that mandatory hydrotesting must always FOLLOW tumbling. However, recent research has shown that tumbling a steel tank continuously for over two weeks removes so little metal that NO significant decrease in wall strength occurs! Clearly, normal tumbling times and procedures should NOT harm a tank. The upshot of this is that hydrotesting is NOT absolutely mandated after normal tumbling! On the other hand, any serious pitting or other internal degeneration that is exposed by the tumbling process may dictate a subsequent hydrotest even if the tank is not “out of date”. The bottom line is that each shop must work up a set of guidelines regarding hydrotesting versus tumbling based on both experience and common sense. When both operations are done by the same facility, this is a fairly simple matter. When several facilities are involved, a co-operative agreement is usually possible. Obviously, overall safety should ALWAYS be the overriding concern whenever doubt occurs.
Please take you tanks to company that deal with Steel SCUBA Tanks not just Fire Extinguisher only tester--They don't want to deal with you because: "Those darn tanks are heavy"-- I like the one that says he does not pre test (as required by the certificate) that taking the test pressure up to 85% (as Stated in certificate- release then take to full pressure) is considered a full test to me- I loose money if I had to last every steel tank twice-- Twice --no!!! Right!!! Correct!!! the way you are required to!!! We do have several re-tester around that do both (SCUBA & FIRE)- most of the do a good job. AGAIN ASK AROUND!
And if you ask them about how they preform the test: they get all upset; that you are telling them how to do their job..
Just be careful --Remember is tank is your LIFE Line--do you really trust your testing company! Are you just another cylinder to them. Few of us that are in the Scuba Testing business think totally different about testing Scuba Cylinders. Ask around to fellow divers-- Advanced HydroTest Inc.--Cave Diver- Cylinder & Valve Inc.--Cave Diver
I'm sure their are others; but main thing is ask around.
Lowest price is not always the best deal...Is you steel tanks rusted bad (not flash rust) from just getting hydro'ed should not be--we let them dry longer! As a cave diver I don't like rust in my tank--I'm asked that a lot-- (different matter another post maybe!!!)Short answer- Does the rust flake?==too much!!!, if it can flake off it could stop up you valve tube.
My rule is: judgement call! Each cylinder is different! Trust you Re-Tester!
Hope this helps!
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Semper Fi, Cameron David Smith, my son, my hero. 11/9/1989 - 11/13/2010 
Originally Posted by dnscarboro
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