Scuba tanks or dive cylinders manufactured of both aluminum and steel can corrode, experience immense forces, can crack and then fail. Failure is extremely rare, but it can occur and steps need to be taken to make sure your scuba tank and you are safe.

On an annual basis you need to have a visual inspection or VIP completed on your cylinder. This inspection is conducted by your local scuba shop employees who are specifically trained on this procedure.

Every five years your scuba tank is required to have a hydrostatic test. A hydrostatic test is a mechanical test in which your tank is filled to 5/3 of it’s working pressure.

I completed a thorough survey of dozens of dive shops from all regions of the United States and found for a visual inspection costs ranging from $15 – $20. There was little to no variance above or below that.

Similarly what I found for hydrostatic tests were prices ranging from $30 to $45. Most of the hydrostatic tests were right at $40.

Visual Inspection (VIP)

The visual inspection is an internal and external inspection of the tank. Internally the technician drops a bright light inside the cylinder to look for corrosion, cracking, pitting, contaminants or anything else that looks out of the ordinary. We also use a dental mirror to inspect the inside neck of the tank.

Externally the technician is looking for corrosion, cracking and pitting. To do so must remove any decals or bubbling paint to assess the corrosion and look for cracks. That’s why all of your shiny decals are removed when you get a VIP.

Pro Tip: Don’t put decals on your tank, they are required to be removed to conduct the visual inspection. Sometimes they are really difficult to remove and the technician will have to use a paint scraper to get them off. Often paint comes off in this process and just looks kind of junky.

I have performed hundreds of these inspections, and the vast majority of the time we find nothing, or just a little external corrosion.

After your tank passes the VIP a decal is applied as proof to anyone filling your cylinder that a visual inspection has been completed within the last year.

If it does not pass further steps may be needed to put it back into operation, or in the event severe pitting or a crack is found it will be removed from service. This is rare, but it does happen.

Hydrostatic Testing

As mentioned above a hydrostatic test is a mechanical test where the tank is filled with water to a pressure that is 5/3 of its working pressure. So if a tank operating pressure is 3000 psi the tank is filled to 5000 psi. This is done inside a special tank filled with water so if there is catastrophic failure it isn’t a danger to anyone.

Most dive shops do not have the facilities to complete hydrostatic testing of cylinders, they send it out to a vendor who does the testing. These companies test tanks for welding, medical, etc.

The test is measuring the elasticity of the metal and the flexing of the tank walls. If the walls flex and then flex back to a desired tolerance the tank passes the test. If the walls do not flex or do not flex back to the desired tolerance it is rendered inoperable.

The first hydrostatic test is completed right after manufacturing. Without this initial test the tank cannot legally be sold.

The other way a tank can fail a hydrostatic test is through catastrophic failure, meaning the tank burst under pressure. Usually this happens at the top or bottom of the tank.

When a tank passes the hydrostatic test the date of the test is stamped into the metal just below the neck of the tank. You can look at every tank to see how many hydrostatic tests it has completed and when they were conducted.

Tumbling

As mentioned above, sometimes corrosion or contamination can be found during a visual inspection. Tumbling a tank is done by filling the scuba tank with media, usually small stones or glass beads, and turning the tank over and over. The media scrubs and polishes the inside surface of the tank removing any corrosion or contamination, restoring the interior of the tank to a pristine environment.

I once found oil in a batch of tanks I was inspecting. It turned out to be a compressor with an oil leak. This could have resulted in a serious situation. All of the tanks were tumbled and the compressor was fixed.

The cost to have a tank tumbled is usually right around $50.

How Long Will a Scuba Tank Last

According to Luxfer, one of the major scuba tank manufacturers in the world, their scuba cylinders are cycle-tested to 100,000 cycles at service pressure. This means that if you dive three times per day it would take you 89 years to go through 100,000 cycles.

This is in a pristine environment, not subject to salt corrosion. But there are many scuba cylinders more than 50 years old still in service. I personally have a couple that are 30 years old that are still in service.

I think usage in fresh vs. salt water plays a role in how long a scuba tank will last. Fresh water just does not cause as much corrosion as salt water. This is why a tank should ideally be rinsed with fresh water after each use.

With regular care and maintenance a scuba tank should last you a long time.

A few recommendations are:

• Handle your tanks with care
• Do not overfill a tank
• Have it visually inspected every year
• Look for signs of corrosion
• Rinse with fresh water after every salt water dive