Air in fresh water line

[autumnbreeze27]

I've got 2 fresh water tanks with shutoffs plumbed to a T, from the T it goes to a water filter, then to a water pump.

I've got air bubbles entering the system at the water filter. It goes in fine on the input side, but the exit side I get bubbles. I've tried replacing the nylon fitting, but that hasn't helped. I'm guessing I've got an air leak, but could it be the filter housing is cracked? I can't seem to get it to stop. Do I need more plumbers tape on the nylon threads?

It's just a simple GE Smartfilter housing.