Water Softener Pipe Threads: Tapered or Straight?

[GLT]

I installed a new softener and used 1 inch PEX to run new water lines. All went great, except for two very slow leaks between water softener connecter and the brass female pipe (NPT) to PEX fitting. Leaks about 1 drop every 5 minutes, tightening the fittings has not really changed the rate.
The valve is a Fleck 5810 and the outlet fitting is a Fleck bypass to 1 inch pipe, I find nothing that referring to NPT or NPS.

Are the 1 inch plastic male outlets from the water softener straight threads that require a rubber gasket to seal or are they tapered thread and I just need to tighten them more? (I used Teflon tape 4 times around and they are really quite tight right now).

Thanks for the advice.

 

[Reach4]

If you look at the service manual, you will see
61991-01 .....................Connector Assy, 1" NPT

However like water heater nipples, I think you can use them with a gasketed connector too. I am not a pro.

I had problems with that leak also. I would consider using both good PTFE tape and plastic-safe pipe dope such as Megaloc.
https://terrylove.com/forums/index.php?threads/whats-the-dope-on-pipe-dope.80299/

Rectorseal #5 is not for plastics.

 

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[ditttohead]

Remove, teflon tape 6 wraps, then tighten solidly, it will be fine.