Excuse the novice question. I am installing an old-fashioned bridge-style kitchen faucet that has two chrome-plated brass inlet adapters that, on the bottom end, are flanged and mount to the countertop, and at the top end, have 1-1/8" threaded ends that mount to the valve body with a rubber washer. The inlet adapters have 1/2" female NPT threads for the cold and hot water supply. I have two 1/2" male NPT brass close nipples, 3" long, to extend from the inlets through the countertop. I understand the nipples thread to the faucet inlets via tapered threads creating an interference fit. This much I get.

But the other end of the nipple and its connection to the water supply is causing me confusion and I want to make sure I get this right. Can I attach a standard flex supply hose to the nipple (the kind of flex hose with 1/2" female spin nut and conical rubber washer)? I know that the supply hose will technically fit and will tighten to the nipple (I've tried it), but I seem to understand that there is a different interface for that type of fitting, where the pipe's end is smooth and beveled (like you see on a shut-off valve). Whereas, the nipple end is not particularly smooth and beveled, it's just a standard nipple end. It seems from my limited understanding that there are two different interfaces that use the same threads, one designed for either compression fittings using straight pipe and a compression ferule, or a flex hose with conical washer, and the other for thread to thread direct connection without washer (via the thread taper). Is there such thing as, and do I need to use, a female 1/2" NPT to male threaded compression adapter between the nipple and flex hose?



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This is the part that I *think* I need between the 1/2" NPT nipple and flex supply hose:

[www.suremarineservice.com]

But fueling my confusion is this home depot listing for this flex hose, which states that the 1/2" end threads to faucets with 1/2 MPT, which is what the nipples are. So according to this, I don't need an adapter.

[www.homedepot.com]

If others can confirm (or refute!), much appreciated.



Edited 4 times.

just thread the nut from the flexible faucet supply right onto the brass nipple. the cone shaped washer will make a fine seal.

Thank you! I was overthinking the interface differences.



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the threads are the same but the faucet has a running thread so the fastening nut will spin all the way up to secure it while the nipple threads taper slightly to make a seal when screwed into a fitting.