Buying a used tank?

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

it'll handle it. the burst disk is rated to 5/3rd's I think. (without looking it up).

However, read the above and you'll see that the convertible valves aren't available in the same thread hole size.

Yeah I know about the thread size. That's a different issue. I'm just wondering about the comment of only filling the cylinder to 3442 rather than 3500 because the valve is different.
 
Yeah I know about the thread size. That's a different issue. I'm just wondering about the comment of only filling the cylinder to 3442 rather than 3500 because the valve is different.

go read any of the threads about over filling tanks.... you'll see pages of arguments.

I'm with you though. an extra 68psi is not going to blow the burst disc.
 
I have the opportunity to purchased a ss Sherwood Genesis 120cf tank for $150. The seller says the tank is within date for hydro and VIS.

Is this considered a good deal? Is it worth the chance? I used to service fire extinguishers and can find external damage easily enough.


Phil

The simple answer is:

Don't do it.

It is not worth the hassle.

Buying a used tank can be a good deal, but you must know what you are doing. If you don't know what you are doing, you will almost always lose.

For instance, using a 100cf HP 3442 steel tank as an example:

Let's say you find a used 100cf HP 3442 steel tank for $275.00. That sound like a good deal, after all, it is still in hydro. But the question is how far "in" is it. If it has to be hydro'd in 2 years, then it not such a great deal - in fact I'd pass it up with hydro costing $35.00. And you are not getting a new tank, and you might get it opened up for it's vis and find rust - now it needs to be tumbled - cleaned out.

Or how about a tank for $200.00 that is out of hydro? Even if they guaranteed that it would pass, you may still have to put @ $50.00 into it, and now you have a used tank that cost you $250.00. Is it really worth it?

I'd probably pay (and have) $200 for a tank that is 3 years from hydro and had just passed a vis.

But keep in mind the following:

A new 100cf HP 3442 steel tank cost new about $350.00. Some places will give you a free fill card - 10 fills at $5 a fill is worth $50.00. Now you have a brand new tank w/warranty for $300.00.

Also, I'm using an example of a tank that I'm very familiar with because I own a number of them dive them weekly. Coming across an unfamiliar tank ? - well, it's just not worth it.
 
Don't do it.

It is not worth the hassle.

Buying a used tank can be a good deal, but you must know what you are doing. If you don't know what you are doing, you will almost always lose.

I disagree to a point. While with buying any used item it is good to be savvy consumer I think the above is a bit Pollyanna. Cylinders are pretty damn robust. Yeah, water inside is their worst enemy. However, it is pretty easy to pop the top and stick a small flashlight down in them to inspect. Which is a lot easier than buying a used reg - which will cost far more to rebuild than a cylinder.


If a seller will not let you pop the top to take a look then walk away. If they do and it looks at all questionable walk away from the sale. So what is questionable? Each has their own standard but a simple rule anything larger than about 5mm I say take it to a more knowledgeable person. I doubt that any seller that comes to your door would balk at that if they really want the sale - kinda of like taking a car to a mechanic before you buy it.

As for the examples yeah you can pick cylinders for a deal at $250 but the price is $150 which is descent even if it needs a hydro in two years. But as always YMMV.

BTW - In the past 4 years after a discussion with the seller I have bought 6 used cylinders inside unseen. All pristine inside - including 2 old 72s that had been sitting for almost 35 years. Oddly 1 of them failed hydro, it sibling passed but barely. Fortunately, those cylinders ended up being free for other reasons.
 
All pristine inside - including 2 old 72s that had been sitting for almost 35 years. Oddly 1 of them failed hydro, it sibling passed but barely. Fortunately, those cylinders ended up being free for other reasons.

I would bet that the 72s were not pre-stretched by the hydro tester. It's not a regulation that they do that, but it is recommended by PST for the galvanized cylinders, I'm sure you know that.

If the tester did not condemn the cylinder, testing it again, with the PST procedure, might be worth trying.
 
They both were pre-stretched to 90%. In fact the one that failed at the 90% mark. But for the test to be valid he then did the full 100% which obviously it failed as well. As noted it's sibling did not do much better but passed. Both cylinders were from the same batch and had been doubled up from birth. So given that knowledge I figure that either there was a problem at birth (the mfg??) or along their life (????). Though made in 74, it was their first post birth hydro (they sat untouched with air in them for 35 years). I was bummed cause they were a nice of double. Now one is scrap and the other is in the garage as the around the house I need to inflate something cylinder.
 
Now one is scrap and the other is in the garage as the around the house I need to inflate something cylinder.

Just curious about the cylinder that you keep around as an inflator. How do you get that tank filled? Do you just fill it with an equalizer hose from another tank? I have a spare 72 that I use around the garage, but I have the dive shop fill it once a year at the cost of a visual.
 
I just take it to the shop and have it filled. The hydro is current and I can do the visuals.
 
They both were pre-stretched to 90%. In fact the one that failed at the 90% mark. But for the test to be valid he then did the full 100% which obviously it failed as well.

I have to say that's the first time I've ever heard of a LP72 passing vis but failing hydro. I don't doubt what you're saying at all, it's just that this is a first for me.
 
https://www.shearwater.com/products/perdix-ai/

Back
Top Bottom