Why we won’t fill your tank, and how to make sure we can

The most common reasons we say no

• No visual inspection, or an expired one. This is the most common.
• No hydro test, or an out-of-date one. A close second.
• A damaged valve.
• Air that smells bad. Sometimes someone brings in a tank that was filled somewhere else and the air smells off when we open it. Depending on how bad it is, we’ll tell the customer we need to fully empty the tank before refilling it. Even then, we can’t guarantee the smell will go away, because the cylinder has already picked it up from the compressor that filled it before.

What the inspections actually are

The visual inspection. The inspector takes the valve out of the cylinder and looks at every nook and cranny for cracks, stress, corrosion or anything else that could be a cause for concern. A visual is only a snapshot of the day it was done, so it’s recommended at least once a year. That’s the industry standard most fill stations follow.

The hydro test. A hydrostatic test is a pressure test. The cylinder is filled with water and pressurized above its normal working pressure inside a test chamber, and the tester measures how much it stretches and whether it goes back to its shape. That checks the integrity of the metal and that it isn’t at risk of rupturing. In the US, scuba cylinders are due for a hydro every 5 years.

Neither inspection is a guarantee that nothing will ever go wrong, but they make sure someone is regularly checking that cylinder.

What happens if an out-of-date tank gets filled

We can’t fill an out-of-date tank, period, and our insurance won’t cover it either. If someone has their own compressor and fills an out-of-date cylinder themselves, they’re the one assuming the responsibility if something were to happen.

The real risk is simple: when no one is checking a tank, the chance of something going wrong goes up.

The tank that leaked through its own wall

An experienced diver who didn’t believe in visual or hydro inspections brought us a cylinder. It happened to be within its inspection dates at the time, so we filled it.

While it was filling inside our containment box, we heard air hissing. We stopped the fill, opened the box, and found the neck of the cylinder leaking where it never should. It wasn’t leaking at the connection between the valve and the metal. It was leaking just below the neck, straight through the metal.

A slow leak like that means the metal gave way gradually instead of bursting, which is exactly why we fill inside a containment box. Still, it was a tense, scary moment: you’re putting air into a cylinder and it’s coming out through its walls.

How people react when we say no

Most people are understanding. Usually one of two things happens: they say “let’s do the inspections now,” or they say they weren’t prepared for it and they’ll come back when they can.

Every now and then someone tells us another place will fill it anyway, or that they’ve been doing it this way for years. Doing it for years doesn’t make it safe. It just means nothing has gone wrong yet, and we’re not willing to bet on that.

My tank is out of date. What now?

We can handle it. A visual inspection usually takes 24 to 48 hours, depending on how much work we have. A hydro test takes 7 to 14 days. Air fills are the only thing we do same day, so if you have a dive coming up, bring the tank in early.

Not sure when your tank is due? Check the stickers and stamps on it, or use our Is my gear due? tool.