So I just picked up this 92 gallon corner acrylic on CL for a decent price, just a few scratches that need addressing. I want to fill with water for some time in my garage to do a leak test, but first need to call the FIVE feed/return lines. Not sure why so many. Anyhow, 3 are in the rear corner overflow, two in the bottom of the tank. I have capped them all with teflon tape on the threads, however I seem to be having trouble with a larger black fitting on the rear underneath. The outside of the male threads is 1.5" diameter, but when I tried a 1.5" cap it was too large. Went back for a 1.25" threaded cap which seems the right size, but as gently as I start to thread it, it seems to tight almost stripping feeling after just a few rotations. I don't want to strip the threads if the cap is incorrect and then have leaking. I assumed everything is NPT threads, but could it be something different?
