Hard to seal threaded joint

[loukky]

I am having trouble getting a threaded joint to seal at the base of a tank that holds water, height of tank about 5 feet so not much pressure. This is a 1 1/2" PVC male adapter going into a bulkhead fitting which is black (maybe ABS?). I used teflon tape and teflon paste both when assembling this but still have a slow weep. I have checked the adaptor for cracks as well as the bulkhead. It is a real hassle to disassemble this system and I am to the point I would try a different sealant if there is something recommended. I generally know how tight to do a fitting but this one seems to want to go further than I would prefer, maybe due to the slickness of the teflon and the two different materials, and I don't want to overtighten. Any advice would be appreciated.