Filling a CO2 tank with compressed air?

[Airborne Janitor]

I see two schools of thought in my research: Sure! Or hell no!

 

I'm building a little CO2 onboard air tank I have out of a 5lb CO2 tank that's like new. Like this one:

 

https://a.co/d/6gM4dDB

 

If all components are new and there are no leaks, can you fill this tank with compressed air, from say my Quincy 60gal 2-stager? The tank will be used for airing up tires and air tools in a pinch. 

[Pete M]

the amount of air inside such a tiny tank won't do much of anything.    I borrowed a tiny tank/compressor for putting up trim and that night used it to put some air in a low tire.  took 3 fillups to get it up to 25psi.  C02 is stored as a liquid and so when it turns to gas you get far more volume than the liquid.

[Airborne Janitor]

12 minutes ago, Pete M said:

the amount of air inside such a tiny tank won't do much of anything.    I borrowed a tiny tank/compressor for putting up trim and that night used it to put some air in a low tire.  took 3 fillups to get it up to 25psi.  C02 is stored as a liquid as so when it turns to gas you get far more volume than the liquid.

 

Thats good to know thanks.

[ghetdjc320]

X2 on the CO2. You can just use air in it but you will need much more than 150psi to be useful. CO2 is a much better way to go though

[thecodemonk]

Been using CO2 tanks for 6 years now and love the convenience.  Used the tank off road for truck tires, used it to inflate the inflatable pool, used it on bike tires…it’s easy to pack and cheap to refill (until you need a new tank if you aren’t swapping them out).

 

it’s also nice and fast with a high flow regulator (can use the hvac adjustable regulators) and hose rated for more psi.  Filled my 37s on this last trip from 4 psi to 20 psi in about 20 seconds per tire.

[Eagle]

How about doing a tech side write up with more specifics on the valve and how you set up the tank. Where do you get it filled, and to what pressure?

 

I'm sure other people will be interested.

 

[Pete M]

for C02 I use a standard 20# steel tank filled up at a local welding supply shop.  I use a non-adjustable 100psi regulator with no gauges.  works great for filling tires and blowing a steam of air to clean things.   if you want to use it for things like a brad gun, you'll want an adjustable reg with a gauge. 

[thecodemonk]

EDIT: the more I think about it, you’re right…a write up might be good.  I’ll put one together after the holidays of what I did and useful resources for sizing and such.

————
 

CO2 is used for two bottle setups for mig welding so it’s not uncommon to find a place that can fill it.

 

I’ll see if I can dig up the receipt and get the part number of the regulator I ended up with, but I just fill up or swap out at the local welding supply shop.  Just asked them for an adjustable psi, high flow regulator (since welding is generally lower psi) and they recommended one they had in stock used by hvac guys so I bought it.
 

I just assembled a diy 5# tank while I waited for my 10# smittybuilt to come back from being recertified.  If you use a size they have, you don’t have to wait for a fill, you can just buy the first tank from them and swap your empty tanks for full tanks after that, usually for no added charge. (My local welding shop only carries 5# and 20# sizes so the 10# tank requires me to wait while they fill it or be sent away to be recertified it every five years.)

[jpnjake]

I went to my welding gas supplier a couple months ago and he was shocked that someone so young was using C02. Until I told him we use it on our off-road rigs lol. But it’s still good to weld with in a pinch 

[thecodemonk]

Write-up posted...let me know if I've missed anything or if I should add a FAQ or something.