AL tank stored empty for couple of months

[broncobowsher]

You do realize that new tanks are shipped empty without a valve installed? Nothing bad is going to happen to a tank that is empty. As long as you are not letting stuff get into it, everything is fine. Screw the valve back in and close it, everything is sealed up. It can sit in storage forever like that.

The whole reason why you are told to keep a little pressure in the tanks is that will prevent anything from getting into the tank while in storage. Not that the tank needs it to prevent damage to itself. Just an anti-contamination measure.

 

[halocline]

You do realize that new tanks are shipped empty without a valve installed? Nothing bad is going to happen to a tank that is empty. As long as you are not letting stuff get into it, everything is fine. Screw the valve back in and close it, everything is sealed up. It can sit in storage forever like that.

I think its a little more complicated than that. If it's an AL tank and it doesn't have any condensation or unusually moist air in it, then yes it can sit a long time. But if it's a steel tank, or the air in the environment where it was empty and open is high humidity, it would be better to put a small amount of pressure in it from a scuba tank or scuba compressor, to keep it nice and dry inside. Using couv's $3 coupler and 2 regulators it's very easy to keep some dry pressure in a pony bottle. And you don't have to pay for a fill between trips.

 

[Jack Hammer]

If a tank gets completely emptied underwater it can get water in it, even with a reg attached. Moisture can cause "blooms" in aluminum tanks when pressurized, even freshwater. These are some of the reasons for a visual check when a tank has been empty.

It's ignorant (no offense intended) to imply that because new tanks a shipped empty without a valve installed that the tanks are left open and exposed. They are not. New tanks have plugs installed to keep moisture, debris, critters, and whatever else out of them. I'd have a quick vis done to be sure there are no bugs, dust, or debris gotten into the tank.

 

[broncobowsher]

That is why I stated "screw the valve in and close it". No longer open to the atmosphere.
And it can sit like that with no pressure in it just like it can sit like that with pressure in it.