I am the lucky recipient of a free CO2 bottle from my inlaws. I was going to get it filled and use it on my welder and before anyone says it isn't the best way to weld, I know but it works and I've used it before. The problem is that the tank says it has a siphon tube in it. I presume this is to get the liquid out of the bottom like a propane tank. Is this correct? Can this be removed? Any suggestions to make this work?

When you go get it filled just ask the gas supplier to take the tube out or trade it for a tank without one, I had them remove mine and retest, cost me like $20.

When you go get it filled just ask the gas supplier to take the tube out or trade it for a tank without one, I had them remove mine and retest, cost me like $20.

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forgot to say, you will likely need an adapter to get the CO2 valve to mate up to the argon type fitting on the welder, that is what i had to do

MIG welding with flux-core wire WITH C02 sheilding gas is supposed to give superb penatration.

forgot to say, you will likely need an adapter to get the CO2 valve to mate up to the argon type fitting on the welder, that is what i had to do

Instead of doing this you'd be better off unscrewing the argon bung and putting on the correct one for CO2. Your regulator won't stick out so far and will be less likely to bust off if your tank somehow falls over. Whoever sells you the adapter would also likely have the new fitting.

Technically, you could use it right now if you could figure out a way to safely hold the bottle upside down. You might get some funny looks, but it would work.

If it's a large sized CO2 cylinder, I would leave the siphon tube in it , get a scale and fill valve and you can fill smaller bottles off of it. Forgot the name of it, but Miller makes that one portable MIG that takes a 20oz? paintball cylinder and it's supposedly good for about 20 minutes of weld time. It would be handy to have your own fill station if you owned a setup similar to that.

I only have a small 5lb CO2 cylinder because I don't use very much CO2 . I use a gas mixer/proportioner. With a mixer you just dial whatever % mix you need when you need it so CO2 and Argon aren't mixed until you actually use them. Because I TIG more frequently using 100% Argon my CO2 is shut off most of the time. It's nice to have custom blend Ar/CO2 whenever you need it -I use 8% for spray transfer MIG and around 20% for short circuit. 100% CO2 is a little messy, but it makes a hotter weld than 75/25 and can be used out of position where spray transfer won't work.

The small CO2 cylinder also pulls double duty as a portable "air" tank for filling tires once in a while. Very handy to have.

The valve will usually have an "S" stamped into the body if it's a siphon type. If you don't want it, just ask the LWS if they'll swap it out with a non-siphon type. My LWS swaps "customer owned" cylinders for me all the time. This might be a zero dollar fix.

If you aren't sure how many pounds it holds, take a guess at what cubic foot sized cylinder it most resembles and then divide that number by four. Example: a 10lb CO2 is the approximate size of a 40cf inert gas cylinder. It's a rough estimate, but it works if you're used to dealing in cubic foot sizes.

Hope that helps.

Why not swap it at the local welding shop for a bottle of 75/25? I don't see why they wouldn't do it, my local welding shop will let you trade any in-date tank for any other similar size tank, and any out-of date tank for a similar size plus the re-cert. fee.

Thanks for the responses. I'll have to swing by the welding store and see what I can get done.

Why not swap it at the local welding shop for a bottle of 75/25? I don't see why they wouldn't do it, my local welding shop will let you trade any in-date tank for any other similar size tank, and any out-of date tank for a similar size plus the re-cert. fee.

This will not work usually because CO2 tanks are built to a much lower maximum pressure so they cost less. Plus your welding gas would end up being about 10x more expensive. CO2 really isn't as messy as you hear once you get used to it. It welds hotter so logically you will increase your wire speed to absorb some of the extra heat. I know the 'by the book' pressure vessel welders here will say "go with a mix" but you can get a very strong weld with CO2 and it's super economical. I've never figured out why someone who's about to bounce a truck off a pile of rocks would care about a little splatter. If you get paid for your work then I can see your customer wanting it pretty but for the DIY guys who cares?