I know this topic has been discussed previously and after combing through a bunch of threads I'm still lost. I am a pretty new diver who came across some high pressure steel tanks 80CF and 100CF. They have DIN valves that sit at kind of a 45 degree angle to the top of the tank. Stampings on the tank say 3500. Can I simply use an adapter to mate with my (yolk) first stage which is an Aeris Ion? Do I need a new valve or a new first stage?
First of all, a yoke-configured reg can only mate up with a yoke-configured tank valve. There are several brands of DIN/K convertible tank valves on the market that use a screw-in yoke insert. The older the tank valve is, the less of a chance it's one of these convenient DIN/K convertible valves.
Secondly, I have a couple of PST HP steel tanks with DIN valves that have a 45° angle to them. The neck opening on the tanks is slightly smaller than 3/4" NPS Worthington HP steel tanks (XS Scuba branded) that are commonly sold nowadays. The valves on my PST tanks are 7/8" UNF and are branded as Sherwood 6300 or U.S. Divers/Aqualung. If you have these tank valves, the most convenient option for you would be to convert your Aeris Ion first stage to DIN. Talk to your preferred Aeris authorized dealer about making this conversion. Similar conversion parts in other regs cost $50-$90.
Dive Gear Express has a nice essay on regulator fittings and tank neck thread sizes.
Take a picture of your tank valves and attach it to a post in this thread. If we see the tank valve, we can confirm what your options are.
If you don't own the tanks yet and are considering purchasing them used, you should be aware of any additional costs that you will incur to make them dive-able. This includes hydrotests and annual visual inspections (VIPs). Hydrostatic tests are required every 5 years. They cost $15-$40 per tank, and there's no guarantee that the tank will pass this test. With the PST tanks in particular, it's best to verify that testing shop is up to speed on the current recommended testing parameters for the tank. I believe that the PST tanks require a special pre-expansion test. It's advisable to print out the testing procedure for this tank and verify that the facility is aware of it...or else you run the risk of the facility failing a perfectly acceptable tank.
Here's a link to an older tech bulletin for hydrotesting PST HP steel tanks.
Visual tank inspections are required annually. They generally cost $8-$20 per tank. Tank inspectors remove the valve and look inside to verify that the inside of the tank is free of corrosion. Typically, they change out the tank neck o-ring and verify function of the tank valve as part of the inspection. VIPs do not normally include an overhaul of the tank valve.
If the tanks still need to pass hydro or VIP, then I would negotiate the sale to be contingent upon the tanks passing those tests. Speak to the seller about this
before agreeing to buy the tanks.
