These kayfun tank sections can be quite hard to unscrew. What makes them so hard to unscrew is the orings are gripping to each item they are in contact with. You can put the Kayfun in a freezer for maybe ten minutes and the oring will become hard and not stick to the parts as strong. This will really help if two parts have been screwed together with too much force.
To prove that the orings are the problem, try screwing two of the tank sections together without the oring and see how easy they unscrew.
What works really good and I always use is two strips I cut from a rubber disc used for opening jar lids.
Just use one strip under your fingers on each piece you are trying to unscrew.
You can buy the rubber discs from Bed, Bath and Beyond for a couple of dollars. They also work good for removing a stuck drip tip.
With these rubber strips the freezer method is not needed unless the sections have been assembled with way too much force.
know what i have 2 rubber bungey straps in my closet that i could cut one of those and use. i got them when i wrecked my truck in the ditch this past december it was december 13th 2013 and it bent the frame so bad the door wouldn't shut so the tow guys had to bungey the driver door shut. lol i fixed the truck some money spent at a frame shop and 4 weeks later and i was driving it again that chevy s10 is a trooper. she is almost at 300k miles.
have to include pics






lol it was quite a ride
but i was driving down a real slick road to a doc appointment pre surgery and i was doing around 35mph in 4th gear well i could still feel the wheels slipping so i thought i need to slow down even more so i went and shifted to 3rd gear and when i let off the clutch there was enough rpm to break the rear end loose and then it went completely sideways then i turned the wheel and it did a 360 around the cab and flew into the ditch