RO line keeps popping out of float switch

[asylumdown]

I just used a pair of pliers to tighten the nut as far as it would possibly go without breaking it. I had previously had it tightened as far as my fingers could tighten it, but it had another full turn and a half in it with the pliers. I can still pull the tube out relatively easily though, is that normal?

And I'm not sure what brand it is, it's whatever brand Rd Coral Calgary used to sell.