Hey all. It's a long story but I'm redoing a mixed black/grey (solo) holding tank on our latest micro-trailer and making it strictly grey and then adding a cartridge toilet instead. The existing tank was leaky, the single mixed tank wasn't ideal, and when I dropped it, it didn't take me long to figure out why it was leaky - the installation (either factory, or some previous owners modification) was a gong show with caulking trying to make up for it.
Anyhow, I have the tank at a reputable plastic welding shop getting returned to basically new (and hole-less) condition. It's in otherwise good condition and was a waste to throw away when I could get it fully repaired for 1/3 the cost.
For the revised setup I need 3 (probably 1" will be fine) holes on the top of the tank near where the toilet used to drain into. 1 for the galley sink, 1 for the shower, and 1 for the vent.
I'm struggling to figure out what fittings may work best for mating onto a flush ABS surface. Ideally I want them as flush as possible, and threaded - that way I can adapt whatever fittings I need externally beyond that point.
Anyone have any suggestions?