Switching tanks for every dive?

[cvrle1]

Tried to figure this one out my self, but couldn't come with any explanation that made sense, so wanted to see what everyone else thinks.

During my OW training we would switch the tanks after every dive, which was fine since we ended up with less then 1K PSI. One time though we did a short dive just for our skills and when we were done we had over 1500 PSI. When we switched the tanks I asked how come since we had more then 1/2 the tank left and we were going to go for just a fun dive. Answer I got was that it's just a good practice to do.

Now, other then the stores getting more money for fills, and "just cause" answers, can anyone comment on why would you not use up the rest of the air in your tank (provided it would be enough to cover for the next dive) and switch to the new one.

Thanks

[scubadiver888]

One good reason is, if something went wrong (free flow, buddy ran out of air, etc.) it would be better to have a full tank rather than a half tank.

[No Misses]

Most new OW divers tend to suck air.
Let's do some simple math.
For this example, we will assume that a full cylinder will last 30 minutes at the depth you were diving. You go from 3000 PSI to 500 PSI in 30 minutes. You could restate this as using 2500 PSI in 30 minutes. A half full cylinder has 1500 PSI. If you want to have 500 PSI remaining when you end your dive, that only gives you 1000 PSI to use. That is going to be a short dive. JM2psi

[ektess1]

There is no 'reason' to switch tanks other than the requirement of enough gas to do the dive. It does not go bad. i can get two dives out of one tank depending on the situation.
In your situation it made it earier for the instuctor not to worry about who was going to run out of gas.
When you are done with your training, you can use whatever tank you have however long you want. So long as you have enough gas to get you down and back up. The back up part is the most important part.

[crosseyed95]

Originally Posted by No Misses

Most new OW divers tend to suck air.
Let's do some simple math.
For this example, we will assume that a full cylinder will last 30 minutes at the depth you were diving. You go from 3000 PSI to 500 PSI in 30 minutes. You could restate this as using 2500 PSI in 30 minutes. A half full cylinder has 1500 PSI. If you want to have 500 PSI remaining when you end your dive, that only gives you 1000 PSI to use. That is going to be a short dive. JM2psi

Pretty much standard operating procedure. As No Misses said, OW divers tend to suck air. Also, instructors do change their minds sometimes during dives so maybe the instructor had planned on doing a longer dive (just guessing on this one).

When I assist my local instructor, our procedure is to always change tanks between dives. Doesn't matter how much air they have left or how short the dive will be. This, as you said, is to give the new divers practice on changing out tanks.

crosseyed95

crosseyed95

[Suther2136]

I n my OW test dives we reused one tank for two short checkout dives. But the deepest part of the quarry we were in was 26 ft.

[Rhino]

We did the same thing during OW certification. I guess that it's standard procedure.

[DMWiz]

I seriously doubt your shop is trying to make more money on fills from students since they price of the class usually includes all the fills you will need for the class.

If you're going on a "fun" dive wouldn't you want that to be on a long(er) dive? No Misses hit it right on the nose. Besides, repetition makes it second nature.

You often see new divers with loose tanks, if your instructor observes you replacing your tank he can assist you and point out possible pit falls such as loose cam bands or improperly threaded cam bands etc.

[cvrle1]

Thanks for all the replies. It makes sense to change the tank, but I just wanted to see if there was any other reason to switch other then it's better to go with full then 1/2 empty (for all the reasons mentioned)

[fisheater]

Probably the simplest answer is that cr@p happens. And when it happens, you're MUCH better off with more air.