The design makes it hard to remove.

The removal tool is designed to use both hands to turn the canister.

 

What does the tool look like? If just a design issue i will have to accept and use "big" stuff to take it off - I have read people using cheater pipes on the end of breaker bars and ratchets for leverage. Last time i used a 1/2" drive ratchet with cup style wrench on the end - took a lot of muscle!
Thank You

 

The tool has a pipe type tee handle such as a two handed water main handle, a pipe shaft and cup for the canister. This allows two hands to be used for greater force and having a wide tee handle greater leverage.