I have that trouble, too, because of the pressure build-up. Being an older woman, I don't have the strength to use a long screwdriver or something for leverage any more. Instead, I loosen the hose connection to release the pressure inside. Then the top screws off easily. It's a nuisance because you have to tighten the hose again, but it works. I used to take it over to my brother's farm to use the vise and crowbar, but I was quite happy to figure this out.
Also, before your first use (and at other times), if you put some vaseline on the hose connection before you screw it on, it will seal it better. My dad taught me that years ago.
Sounds like you tightened it too much. I usually put the bottle between my legs and turn the handle. works for me...... If you can't ask someone for help who may be stronger...... Good Luck.
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