What type of fitting do I need for this?

[turbo2oh]

I'm trying to hookup my return plumbing and can't seem to find the right fitting. It says 3/4" uPVC and I bought a 3/4" union to hook up to it and it doesn't fit.

The original one (right) fits the jet plumbing, as well as the new 3/4" union.
The male part of the new 3/4" union (left) doesn't fit the plumbing (top), though it appears to be the right size. The threads just don't engage.

The threading seems a lot shorter on the original (right), not sure if that makes a difference.

What type of fitting do I need to hook up to it? A simpler way to phrase this might be what is the fitting on the right? I don't see any identification on it.

 

[SFish]

Sounds like one maybe be standard and the other metric or one maybe a compression fitting. I would take it to the hardware store and ask. That's the only thing I can think to do sorry I can't be more help.

 

[turbo2oh]

Sounds like one maybe be standard and the other metric or one maybe a compression fitting. I would take it to the hardware store and ask. That's the only thing I can think to do sorry I can't be more help.

Yeah maybe. Don't get why the original would fit in the new union female side though.

 

[turbo2oh]

I just cut it off. Not worth it to try to figure it out.