Tank Questions

[NCMtnDiver]

I have a couple of tank questions. I know this info has probably already been discussed, so I apologize if I'm re-asking already-answered questions. How long is air good in a tank? I finished the dive season last summer with air still left in my tank, is it OK to dive with even though it's sat for months? It seems like my local dive shop owner said it was fine, but I thought I'd see what everyone else thought.

My next question is concerning snorkel tubes. One of my tanks had a sound in it like something rolling around inside, which turned out to be the snorkel tube. I don't know what the snorkel tube does exactly, but it's making that sound again (come loose?). Do I need to have a dive shop look at it before diving with it? This might be a really dumb question, I know....

Thanks!

 

[Papa_Bear]

Unless contaminated air does not go bad! The snorkel keeps objects or rust etc from blocking the valve opening in the head down configuration.....

 

[battles2a5]

The air in your tank should be fine. The snorkel tube is there to make sure debris doesn't become lodged in the valve. It just threads into the bottom of the valve. If you LDS "fixed" this and you are already having issues, you may want to look into another LDS.

 

[NCMtnDiver]

Thanks for the reply. So it sounds like I'm OK on both things for now. I would just take the tank to my dive shop, but it's 2 hours away.

 

[marchand]

Have the air analyzed, and if it is still 21% O2 (or whatever you had it filled with) then it should be fine.

As long as there is no water or loose rust in the tank the dip tube rolling around wont cause any problems. If the tank is full then use the tank before you take it to the shop to have it reattached.

 

[ClayJar]

My next question is concerning snorkel tubes. One of my tanks had a sound in it like something rolling around inside, which turned out to be the snorkel tube. I don't know what the snorkel tube does exactly, but it's making that sound again (come loose?). Do I need to have a dive shop look at it before diving with it? This might be a really dumb question, I know....

The "snorkel tube" (or dip tube) is about two inches long. The idea behind it is that when the valve is down, the opening in the end of the tube will be a couple inches above any contaminants in the cylinder. The tube is part #15 on this diagram from Dive Rite Express (and it simply screws into the hole on the base of part #14):

Dive Rite Express​

As you can see, if you go valve-down without the tube in place, any contaminants will go right into the valve. If the contamination is not sufficient to get clogged up in the valve, it will go from there right into your first stage regulator. Then it'll either get filtered by your first stage's filter (possibly clogging it enough to cause airflow problems) or get through and possibly cause problems in your first stage. I've seen very small amounts of free powdery corrosion in even very well cared for cylinders (even without a loose dip tube knocking around inside), and it doesn't take much getting to the first stage inlet to start causing problems.

I would strongly advise against diving a cylinder with *any* internal noises, especially if it may be the dip tube. If the shop "fixed" the problem previously, only to have it return, I would certainly expect them to pull the valve and correct the problem. They would do this in my presence, and I would be quite interested to hear the explanation of what happened. Regardless, even if I had to "waste" a fill and pay for an "early" visual inspection, that would be a very small price to pay. You may not have any problems diving a cylinder with a valve missing its dip tube, but the problems that *could* arise are significant enough for it to be a foolish wager.

 

[Isaac-1]

Air in tanks can go bad, but it takes a long time (usualy years), I had a tank that sat stored 2/3 full for over a decade (it was behind other things and I forgot I had it), I smelled the air that came out of it, and it was BAD.

Ike

 

[NCMtnDiver]

Thanks everyone for the info. I have another tank that I have to take in for a visual inspection, I'll just go ahead and do the other one too.