CO2 Tanks

Can you only use tanks for CO2 or can you use an old oxygen tank?

Pressure is pressure but if it is an old tank you would probably have to pay to get it certified before anyone would fill it. I had an old scuba tank that I thought I could use for kegging but I ended buying a average (don't know the size) kegging CO2 tank because it might have cost me more or the same to get the other one certified.

The "older" tanks, the steel ones that are refereed to as 20cf. for oxygen and 5 lb. for Co2 service are the same tanks. The tanks have different valves and burst disks (pressure safety device) due to there different operating pressures.

The industrial O2 valve is a CGA (Compressed Gas Association) 540 and the Co2 valve is a CGA 320.

If you have an "old" O2 tank it can be converted or exchanged at most welding supply shops. If it is out of test (10 years on O2 5 years on Co2) you will more than likely have to pay for the re-certification (hydrostatic test) for the cylinder.

If you take it to a welding/gas store they'll probably let you swap it out for the other gas you want.