Im sure many of new divers have questions about buying tanks online whether it is from a scuba specific website or from someone who might be happening to sell their tanks. I am making this thread and hoping that people will post what they have learned about buying tanks online and some do's and dont's.
All but 2 of our 11 tanks were purchased used, and I have purchased 18 tanks used where many were passed on to friends. Visual inspections I could careless about, but hydro is something to pay attention to. Hydro's can be done fairly cheaply from places that service fire extinguishers. Our local business charges $17 per tank. Dive shops often charge $40+. Just factor it into the cost of the tank.
For most any dive shop to fill a tank they will require a visual sticker. This is not a law, but a dive shop thing and you will conform. Their compressor, their rules. Got it? Vis stickers can be purchased from vendors, but the dive shop has to accept them. Visuals must also be performed for you to know your tank is in good condition. Most dive shops charge $10 or so. If you do vis your own tanks you will need a fill whip or some way to put pressure back into the tank before bringing it to the dive shop.
When buying a tank, don't be afraid to ask if you can drain it and take a look inside. Drain the tank slowly. We have gotten a discount due to slight rust on the inside of the tank. This is only going to apply to steel tanks. Aluminum tanks are for stage bottles, not for back gas. Aluminum tanks are cheaper to buy, but require a person to carry more weight. Knocking the valve off can usually be done with the palm of your hand once the tank is drained. Sometimes it might require a wrench, or a harder smack which is not recommended. A bright flashlight will let you see the walls and bottom of the tank. Pitting is bad, but surface rust is almost considered normal. Hydro's are done with water in the tank and therefore can leave some flash rust.
The two main brands I look for are Worthington and PST, with Worthington being my favorite. There are other brands I wouldn't rule out but be careful since some are only 300bar DIN connectors. There are 7/8" and 3/4" neck sizes with the 3/4" being the most common today. A set of doubles can easily be split up into single tanks again with just two plugs. Factor sale of the bands out of the tank cost. Personally I want hot dip galvanized tanks, not painted.
All of our regs are DIN and we swap the fittings back to yoke when traveling. No adapters required even though we own a couple.
There are many places to buy tanks. Craigslist is awesome. Ebay, and many tanks are sold on forums like this one. Shipping is a non issue if you can get the other party to agree to ship. I cut the shipping tags myself (You can do it for both UPS and USPS), then email them for the other party to print. The valve must be removed and wrapped up, with the ends of the tank also being protected. Otherwise not much damage can happen in shipping as long as the box stays together. They are steel after all.
Just what kind of deals can you expect? How about HP130's for $160 each in near perfect condition. HP100's for $150 each. Ebay landed me an HP100 for $140 brand new minus a valve, that I already had to use which was removed to make doubles. HP80's for $100 each, as new but out of hydro. The list goes on and on. Of course the local dive shop would happily sell you these same tanks new for over $300-$400 each. A 50% savings for an item that should last 50+ years, I will take it. Often you can find deals on new tanks that have sat around in a dive shop for too long and they just want to unload them and update their inventory.
