High Temp Union not threading in completely to Matrix pump inlet

[beggehorn]

We are upgrading our pool with a Hayward Matrix 1.5HP Dual Speed pump and I ordered some Custom Molded 21063-154-000 1.5" MIP x 1.5" PVC Hi-Temp Unions for the pump connections. While these unions fit the outlet of the pump nicely, they don't hand tighten into the inlet far enough for the rubber gasket to make a seal. Has anyone run into this issue? I've tried switching the unions around and it doesn't make any difference... I will also be putting some teflon tape around the threads so it will likely be water tight without the gaskets help but I can't figure out why the two female ports on the pump aren't accepting the union threads the same.

???

 

[1poolman1]

We are upgrading our pool with a Hayward Matrix 1.5HP Dual Speed pump and I ordered some Custom Molded 21063-154-000 1.5" MIP x 1.5" PVC Hi-Temp Unions for the pump connections. While these unions fit the outlet of the pump nicely, they don't hand tighten into the inlet far enough for the rubber gasket to make a seal. Has anyone run into this issue? I've tried switching the unions around and it doesn't make any difference... I will also be putting some teflon tape around the threads so it will likely be water tight without the gaskets help but I can't figure out why the two female ports on the pump aren't accepting the union threads the same.

???

While pumps designed for in-ground pool use have threaded ports that extend all the way through the pump pot, most above-ground models have a "stop" at the end with many having a flap that acts as a check valve. That's probably what you are hitting that doesn't allow the O ring to seal. Can't tell from the pictures of that pot, but it may be the issue you are having.
It will take a lot of Teflon tape to seal the threads on those unions. They are not pipe threads, which are tapered and get larger as the part goes into the pump, but straight with just enough "bite" to tighten completely against an O ring in a port designed for them

 

[beggehorn]

Ok, thanks. I guess I should be using the Hayward SP1500UNPAK2 unions.