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Old 04-01-2023, 01:27 PM   #5
Tim Ayers
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Join Date: May 2010
Location: NJ
Posts: 6,916
Default Re: Heater hose connection in head. Brass plug fitment

Quote:
Originally Posted by Brian View Post
What you're doing wrong is using the wrong plugs...5/8 UNF has 18 threads per inch, 3/8 National pipe thread has 18 TPI too. So, I'm assuming that the tap you are using is 5/8 UNF and your plugs are indeed pipe thread.
I believe Brian is right. Those holes in the head should be 3/8” pipe thread
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