I have been refilling the disposable 1 lb tanks for the last thirty years. I use about 8 tanks a year. That is about a thousnd dollars I saved by refilling.
As already mentioned, after a few refills, the valves do not seal tightly any more and the tanks have to be replaced.
I work at a moving and storage company and get a few 1 lb tanks for free when customers abandon their belongings in storage. I use them to replace the old tired tanks with the leaking valves.
