Just replace the bulkhead. You could try tightening it first but honestly plumbers putty,silicone,etc.... should not be needed to fix a bulkhead. If it leaks then replace it. I have a bunch of them and could bring one by tonight if you want. I am working at the Best Buy on 41 right down from you in Acworth. So I take Chastain then north on 41 past SWC......LMK