Rheem RTGH-RH11DV with built in recirculation : what is the fitting type for the recirculation port?

[Mike89]

I have had this water heater for 4 years now, no real issues (aside from water temp fluctuations when someone turn on a hot water tap when I am in the shower). I suspect this is typical for natural gas gas tankless water heaters, please comment if it is not.

My current issue is the unit came with a built-in recirculation pump, and while I had the plumber run a dedicated 1/2 inch return line, I have yet to connect it. In my last attempt I found out the return line port on the Rheem unit was NOT 3/4" NPT (in this case not 3/4" MPT). I tried attaching a 3/4" FPT to it and it leaked like a sieve, even with copious amounts of teflon tape..

It looks like 3/4" straight thread, which to me is similar to a garden hose end, and would need a rubber gasket to create the seal? Does this sound right? Can anyone recommend a fitting? Ideally I would like a 3/4" straight thread gasketted to 1/2" pex a expansion pipe adapter, but I woul'be be greedy Anything to get me away for this weird thread to a normal NPT thread would work.

I feel like the gasket will have a finite life in a hot water loop, but I don't see many other choices here.

 

[Fitter30]

If the 3/4 screwed on to by hand its nps has the same number of threads 14 as npt and will use a gasket. A box store, Ace hardware might have the fitting plumbing supply that carries Rheem heaters. If the gasket is epdm there would be no problem with temp.

 

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[GReynolds929]

Picture...

 

[Tuttles Revenge]

Only thing I can think they would have straight threads is for a filter port. No way Rheem would make a pressure connection without tapered threads. At least on purpose.

 

[Mike89]

Here is a close up picture. Posted in case the cap type is a clue, ignore the extra thick teflon tape, will probably be fully removed if I can confirm it is a straight thread.