Fittings for holding tank revision.

[PrivatePilot]

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?

[PrivatePilot]

QCMan wrote:
If you are draining a sink into the tank you will need 1 1/4" pipe minimum and 1 1/2" would be ideal. Less and you will be waiting a while to drain as you would be creating a funnel. Likewise, the vent line should be the same size as the drain line even if you use an under sink vent stack with a vent valve on it. Shower should be the size of the fitting that is attached to the shower pan/tub for the same reason as the sink.

Thanks. Not too worried about the sink taking a bit longer to drain, it is quite small - this is a tiny trailer afterall.

I think I found a combination that will work at HD.

[Darryl_Rita]

Talk to the guys at the welding shop, they can spin weld fittings in that will work with the ABS of the trailer.

[QCMan]

If you are draining a sink into the tank you will need 1 1/4" pipe minimum and 1 1/2" would be ideal. Less and you will be waiting a while to drain as you would be creating a funnel. Likewise, the vent line should be the same size as the drain line even if you use an under sink vent stack with a vent valve on it. Shower should be the size of the fitting that is attached to the shower pan/tub for the same reason as the sink.