This is how I remember them going together, I believe I just used my grip strength to twist them the final turns. No tools used.
I was kinda wondering if they are just poor quality bulkheads.
As far as I'm concerned ABS bulkheads are poor quality.....period. They are on thousands of tanks though so clearly they can work. I used Spears on a custom acrylic build and I'll never voluntarily use anything else in the future. Unfortunately they require a bigger hole in the glass(they are schedule 80 pvc after all) so you can't replace an ABS one with them without redrilling which could be tricky.[/QUOTE]
I've seen this similar problem with many other plumbing fixtures. Modern plumbing is made to finesse together and never over tighten.
As someone previously noted, threaded pipes are tapered. Generally if you turn them all the way flush into the end of a fitting the female side will often rupture, (even without adding the solvent).
For plastic threads, I use Teflon paste out of water, and silicone lubricant for wet (in tank) pipe installations to overcome the friction of plastic to plastic connections. Adding lubricant allows easier tightening; when the pieces stop moving do not proceed further or else the female is likely to split.
Does anyone else believe that "Plumbing" is a four letter word? I have sincerest admiration for the tradesperson who can install modern plumbing fittings and rarely or never report a leak.