If you rent the cost never sleeps. Every year you have to reach into your pocket. About the time your rent comes due will be when the tank is 90% full. So now you won't want to give up the lease. If it's your tank it can sit for years with no cost. TMJ
I have been dealing with Praxair lately and have found my local supplier the easiest to deal with. I own all my bottles (5) except for the large argon tank for TIG welding (you can't buy them). I take my empty and they just switch them out. TSC has used Praxair for the same program, but I don't know what they're doing anymore after changing names (Peavey mart). I stopped shopping there anyway because the entire store and staff were pretty much useless.
Went to my not so local (25minute drive) Linde Canada (formerly Praxair) on Signet Dr. just north of Finch. just walk in place my tank to the side, they take a look and say "you won't get the same tank back"
OK, they bring out a full replacement, I pay just shy of $67 and leave.
Messer Canada Inc. is literally 5 minutes away from me, had terrible reviews online so I avoided going there.
