I see many dive stores that have started the practice of requiring visual inspections to be performed if a tank comes in with less than 500 psi. This practice is just ludicrous in my opinion. If a scuba cylinder unexpectedly loses gas, then yes, a visual inspection should be performed to see if there is something wrong. However, if you breath the tank down to 400 psi, then there is really no need for an inspection.

First, let’s start off with some of the rules and regulations regarding the inspection of scuba cylinders. By Unites States law, all compressed gas cylinders, including scuba, must be visually inspected at the time of hydrostatic testing. Hydrostatic testing is required every 5 years. So, by law, scuba cylinders must be visually inspected every 5 years. The scuba industry has adopted a recommendation by the Compressed Gas Association (CGA) that the cylinders should be visually inspected annually. By following this recommendation, the number of failures in scuba tanks has been greatly reduced. So, scuba cylinders do not need to be visually inspected annually. However, the annual inspection is a good thing and the practice should be continued.

The argument is that if the scuba cylinder’s pressure drops below 500 psi, then potentially, water or hydrocarbons can enter the cylinder. Ever watch Mythbusters? Many times when they need to propel something, the use air pressure. This air pressure is relatively small, less than 100 psi. Now, if less than 100 psi can propel a small object at hundreds of feet per second, do you really thing that water or dust can enter a scuba cylinder? Not really. Should we be concerned about water entering our scuba cylinders, yes. Especially if we use steel cylinders. That water can cause rust and possibly contaminate our O2 clean cylinders.

If you have taken a gas blending or Nitrox course, you should know how Nitrox is made. One of the most popular methods of blending Nitrox is called partial pressure (PP) blending. With PP blending, the blender first adds pure oxygen in the cylinder, then tops off with air. But in most instances, the scuba cylinder must be drained to empty in order to get the most accurate blend. So if a dive shop that has the policy of requiring a VIP every time your tank goes below 500 psi and they PP blend Nitrox, does that mean they are doing a VIP, and charging your for it, every time you get a Nitrox fill? That’s a very expensive Nitrox fill.

The truth is, that you do not need a VIP if you scuba cylinder falls below 500 psi. If it does so mysteriously, then it does need to be inspected. If you breath it down to empty underwater, it wouldn’t hurt to have it checked just out to be safe. But you shouldn’t have to pay for a VIP if the tank is at 300 psi. This is just another way for a dive store to unnecessary charge their customers. In this tough economy, the more money in your pocket, the better. That $15 for the mandatory VIP could be a couple more air fills so you can go dive again. Ask the person behind the counter why they have that policy. Ask them to prove their arguments. But most of all, be an educated consumer.

I welcome your questions and comments.

Dive Safe,
Duane Johnson
Precision Diving