Plumbing advice

[trilinearmipmap]

I am redoing the plumbing on my 120g tank.

There are two 1" overflows. My question is about attaching the plumbing (1" pvc) underneath the tank, to the threaded bulkhead underneath the tank.

I used a 1" threaded to slip adapter, glued the slip end onto my 1" pvc pipe underneath the tank, then screwed the threaded end of the adapter into the female threads on the undersurface of the bulkhead, using some teflon plumbing tape.

However there is a very slight leak (ie. a few drips every hour or even less) from the connection between the underneath of the bulkhead and the 1" threaded adapter. The bulkhead itself is not leaking.

My question is, should I just try and add more teflon tape then tighten the threaded connection tighter, or should I use pvc cement on the threaded connection?