Gas dip tubes
 

Are there two different gas dip tubes that require different gaskets? One of my kegs seems to have a smaller dip tube and when I try to pressurize it, it leaks.

By smaller, I assume you mean shorter? That's the gas dip tube, and it should use the same o-ring on both the post and between the diptube and keg. If its leaking with a new o-ring, I would check that the flare on the end of the dip tube is not deforemed, and check for nicks on the keg as well.

Does it leak from the poppet or from the threads? If it's the threads, you have a bad o-ring or wrong-sized o-ring. If it's from the poppet (from the top), then you have a poppet o-ring that's shot. The solution is to replace the poppet, as I've never seen replacement poppet o-rings.

M_C

there are two different gas dip tubes dep on the brand of keg

there is a smaller plastic dip tube I believe its for the Challenger line and then a slightly larger, more common metal one but AFAIK they use the same o-ring since my one keg with a plastic dip tube seals fine with the standard diptube o-rings

i'm not sure if the smaller one placed in the wrong keg would cause a leak or not - if so I would assume it would be around the base of the threads

have you tried applying some keg lube? you could also try switching the o-rings for the gas and bev diptubes and see if the leak remains in the same spot

Never mind I somehow put a dip tube gasket on the poppet.