Seems to me it should work but I've never done it - have you?

There are a million safety precautions to make but since this is a home repair group, everyone probably already knows every one of them already.

Dry ice is a lot less expensive at most places when you refill the _smaller_ 5LB CO2 tanks, than when you fill the larger 20LB CO2 tanks usually because of how welding & beverage shops specialize in larger tanks for industrial and commercial users (not homeowners with small 5LB tanks).

At about $2.50 a pound for dry ice, the even smaller sodastream 14.50 ounce CO2 tanks would be even more economical to fill with dry ice than to utilize the refill/swap outfits, where whenever you swap tanks, you lose your brand new shiny unscratched undented tank to get what you get back.

I've never done it but it seems like the process should need only the specified weight of dry ice and a bit of time to let the solid liquefy.

I looked up how to fill the co2 tank with dry ice & found this for the op.

Nor did he cool the valve to shrink it before re-inserting it. Seems like it will increase the number of re-seals that Bob worries about.

I think it impractical to cool the whole cylinder because it's so big, but if the OP does, he will waste slightly less dry ice while filling.

He did cover the frosting that occurs after sublimation & melting, which means you have to put it outside on a hard surface for a day.

But the guy skipped the step of how best to lower pressure to 0.

Looking further, I found this YouTube video of a leaking CO2 tank.

He shows how to get the gas out of the tank without "redecorating" himself. He went outside and opened up the regulator to let all the gas out.

The regulator became cold and frosty by the time he removed the regulator.

I'll keep looking for something that shows how to remove the valve. And replace it.

At the start of the video, did you notice that his thumb bends up. That's true for a lot of people. But other people have thumbs that are in line from one end to the other. I'm surprised we dont' discriminate against one group like we did with left-handed people.

But maybe it's a good thing or I'd have been in trouble

It looks time-consuming. How much money is he saving?

And how did they check for leaks before they invented soap?

It saves time if you don't live near an outfit that fills the tanks, and even if you do it still saves time if you live near the dry ice sellers.

It also saves money but usualy only on the smaller amounts because most of the cost in filling tanks is in the labor so larger tanks cost less per pound of carbon dioxide.

The funny thing is you can make your own dry ice, using any carbon dioxide gas cylinder. And then you can fill it back up again.

Except for the sublimation, if you catch it all, you can go in circles.

Don't believe me? Look at this.