Welding Tips and Tricks

I decided to learn TIG welding around the time that Covid started. Not knowing anything about equipment, I went to the local Airgas outlet and bought a 20cuft argon bottle for $100 (empty). What the salesperson forgot to mention is that the bottle was used & due for hydrostatic testing within 15 months.
Eventually I got around to practicing for a number of hours and now I am out of argon with a bottle due for testing. Trying to figure out what my next move should be so I can continue practicing (and do the occasional weekend repair). Things I am contemplating are either refilling the current bottle or buying a new large filled bottle and somehow disposing of the old one.

a) Google tells me the next time I want to get that bottle filled I will be charged a $30 test fee - is that true when going to Linde or Airgas where they typically do a bottle swaps instead of refills?

b) I read that filling a larger tank (say 120 instead of 20) is comparatively cheaper - is that just due to hazmat fees or is there a difference in rates? Unfortunately none of the large companies have public pricelists and I have not found smaller weld shops in my area.

sorry not sure why your post wasn't showing up.

easy way is to get it tested, then go from there.
i don't know where you are so not sure on your local situation.
over here they are often ruthless on bottle inspection and linde no longer sells bottles, its all rental and exchanged.

I have an 80cf tank that is “owner-owned” and every time I need it refilled, the shop swaps me a new tank, freshly filled.

Now it may be because I have an account with them and do have some leased bottles as well, but I’m unaware of ever being charged a test fee for a small bottle during a swap.

Regarding refilling tanks, yes there is a “base fee” generally charged plus the gas volume. So a 330cf tank may be less per CF than an 80 once you calculate the fee added in.

It may behoove you to setup an account with your LWS anyway. You don’t have to charge anything to it, but it can save you fees and get you discounts on gas. Plus, they’re more likely to swap gas in a pinch or lend a bottle for a day because you have an account.

Most places do sell you welding gases cheaper-per-cubic foot with larger tanks, but it may not be the case everywhere. My supplier has pretty much the same cost/cuft regardless. My main point is that you need to ask the actual suppliers how they work, as they will all be perhaps slightly different. But generally speaking you should be able to get better deals with larger tanks. I personally would not bother with a 20cuft tank at all, but that is just me. At $33 per refill for a 125 ft³ tank of argon, I find be easier than to have to refill a 20 ft³ a lot more often.