I own a commercial propane dealer in California. I am not sure who is doing the "Re-Cert" on the cylinders for you but most fill stations are not authorized to do it. I do not do it because I do not want the liability. The first Re-Cert is visual and there should be no rust around the valve threads, discoloration of the valve and no dents in the cylinder. If there is then the is no good. If it is ok the cylinder must be re-stamped with a current inspection date. Many fill stations / locations just take it in the back, get the steel stamps out and there you go....
It is also important to have a proper " Hydro" done on the tank. These tanks fail all the time. Not so much as blow up but the valves fail and usually as they are setting in front of my business and I have to have a emergency call-out from Amerigas to come contain the gas or the fire dept.
If you take your tank to a location such as Amerigas, Proflame or one of the big boys or a welding supply they can do it and it will be done properly.
The exception to the rule are Marine side mount tanks.
