Be very careful when buying CO2 tanks online (Craigslist). I recently bought three CO2 tanks from one seller on Craigslist. My intention was to flip two of them and use one to boost my plant growth. Turns out, welding supply and gas supply outlets WOULD NOT FILL THE TANKS!
Be on the lookout for any tanks may have previously been owned by vendors.
Be wary of any tanks with even a hint of blue paint on the outside. These may have been pepsi tanks and gas suppliers are not supposed to exchange or fill these tanks. Also look for any vendor stamping. These stamps are in the steel at the top of the tank and may be covered by stickers as was the case with my first fill attempt ("PEPSI" under the CO2 gas label sticker). Any tanks with a new coat of spraypaint (to cover the PEPSI blue paint) will be scrutinized more thoroughly.
My second and third tanks were not painted over, but they did have a vendor stamp hammered out and were rejected for filling.
Also look for the date of last hydrotesting. This will be a month and year number stamped onto the top of the tank. The guy who sold them to me said they had all been recently tested, which was true, but I didn't know how to check.
All said and done, I called PEPSI to find out if best case, they would fill them for me, or worst case, if they would dispose of them for me (can't throw co2 cylinders in the trash/recycle). PEPSI said the tanks may have been stolen and that they wanted the phone number of the guy who sold them to me (the seller works for the company who hydrotests the tanks). I told them that I should probably give him a call first to try to resolve it before getting him in trouble. I called him back, told him about PEPSI wanting his name and number, and that I wanted the problem resolved. He paid me back in full only 30 minutes later! He also gave me a free full vendor stamped tank from the hydrotesting company and put me on a list of people who get rental fees waived (I only pay $16 when I want it refilled!)
I posted pictures of all the tanks. There is one tank with noticeable blue paint (worn off over decades of use), one tank with a fresh coat of black spraypaint and a rubber hub stand around the bottom (also a dead giveaway of a vendor tank), and another tank with the PEPSI stamp hammered out and enough blue paint to warrant scrutiny. All three tanks were unable to be filled. Notice the CO2 stickers (placed over the vendor stamp/hammered out area).
[You must be registered and logged in to see this link.]Just to show my rad plants...
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