Thermal expansion and water hammer arrestor - three questions

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jadnashua

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Tapered NPT requires either pipe dope or PTFE tape to seal...hose connections rely on a washer and compression, just that.

If the seal on the hoses is still intact, you can reuse one, but it's not a bad idea to replace them when doing changes. Some water has more chemicals in it than others, so degradation rate can vary radically from one situation to another, and then, one doesn't know the quality of the devices in the first place.
 

meeotch

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Thanks for the reply, and advice. I did use Oatey tape on both sides of the 1/2" to 3/"4 NPT adapter (and on none of the other connections, which were all 3/8" hose compression ends).

The re-used 3/8" hose I'm less concerned about - if/when it starts to leak, it'll be easy to replace (and I'll buy the right one, next time!)

The adapter connections at the TE tank were more concerning, in that: 1) the 3/4" NPT side ended up needing a washer in order not to leak, and 2) the 1/2" side seemed to be unmatched, in the sense that the adapter is NPT, and the hose claims to be "female straight" thread. (Which I take it means NPS? But other sources describe it as NPT, so maybe the description is misleading.)

In any case, it all seems to be holding. The only minor leak was at the 3/4" connection between the adapter and the TE tank (NPT both sides), and the washer seems to have put a stop to it. The adapter itself was a pain in the ass to find, for some reason. I'll keep checking it, and if I spot a leak, try a different brand of adapter. As mentioned, the one that arrived had some minor chips in a couple of the threads.

All in all, the project cost me only $120, and gave me my preferred tank placement, so a qualified success - thanks to all the great advice I got here!

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jadnashua

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Tape in a straight threaded connection won't seal...it relies on the taper to wedge the PTFE tight to make the seal. Pipe dope should fill it in if it's a setting type and you wait long enough before turning the water on.

The hassles with a rubber gasket is that the rubber can change dimensions some with temperature and age.
 
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