TargetTalk

I bought a new air tank and valve from Champions. I can not find this information on this site or the interweb:

Do you use any thread sealer between the tank and the valve?

Thanks,

NO....
There is a crush gasket that go's between the valve body and the tank. These are a single compression/use item.
I recommend having a dive shop do it. They can then give you a fresh visual inspection and sticker the tank since they unscrew
this valve and check the inside as a part of the visual inspection process. If you are going to get dive shop fills, make it easy for everyone.

Scuba tank? Sealing is done by a large O-ring. The ring should be very lightly lubed with silicone grease (just to keep friction from distorting it as it seats), and the valve hand-tightened. Place a wrench on the valve, and give that a tap with a mallet. Should be all you need.

I second Spektr on this - have a dive shop do it. Done right, a 200 bar tank is nothing to be afraid of. Done wrong, that’s a lot of energy waiting to go bang. It’s a few extra bucks but they have the tools and more importantly the experience to make sure it’s done safely and up to industry standards. Plus, they can fill it at the same time.