3/8 NPT Thread Vs. G1/4" Thread - Whats The Difference??

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#1 · Nov 13, 2008 I'm looking at getting a Res. that has 3/8 NPT threads. All of my other WCing parts are G1/4" threads, whats the difference?? Im assuming my G1/4" fittings won't fit the 3/8 NPT thread?? Sort by Oldest first Oldest first Newest first Most reactions #2 · Nov 13, 2008 No they won't fit without adapters. Almost all WC companies are moving to G1/4". The difference is the threading obviously. #3 · Nov 13, 2008 Technically speaking, there are a few differences: 1. NPT (in general) is a tapered thread, hence the T. It seals as the barb is screwed in and requires friction between the threads to seal properly. Generally, this is achieved by using teflon tape to ensure the threads slide properly between each other and seal. 2. G1/4 is a straight thread (no tapering). This type does NOT seal in the threads, which is why you ALWAYS see G1/4 barbs with an o-ring. The o-ring provides the seal between the barb and threading. This thread type is easier to use because it provides a much more consistent seal when compared to NPT. I'm not surprised it has become (essentially) a watercooling industry standard. #4 · Nov 13, 2008 Quote:

Originally Posted by Burn Technically speaking, there are a few differences: 1. NPT (in general) is a tapered thread, hence the T. It seals as the barb is screwed in and requires friction between the threads to seal properly. Generally, this is achieved by using teflon tape to ensure the threads slide properly between each other and seal. 2. G1/4 is a straight thread (no tapering). This type does NOT seal in the threads, which is why you ALWAYS see G1/4 barbs with an o-ring. The o-ring provides the seal between the barb and threading. This thread type is easier to use because it provides a much more consistent seal when compared to NPT. I'm not surprised it has become (essentially) a watercooling industry standard.

he hit it on the head plus you did anwser your own questions too 3/8 doesnt = 1/4 #5 · Nov 13, 2008 doh.....i mean, i kinda figured it wouldn't fit, i just wasn't sure if they were different standards but happen to actually fit or something like that. anyways, thanks guys...love this forum! #6 · Nov 13, 2008 3/8 npt is much bigger. G1/4 is mean't for rubber O-Rings, because the thread is even. The NPT thread is tapered, so really it's meant to be jammed in without an O-ring. 3/8npt 5/8 barbs have higher flow than even the bitspower 1/4" 1/2" barbs. I picked up really nice nickel plated npt barbs for my swiftech radiator. #7 · Nov 13, 2008 Just to toss in one extra tidbit... most of the time you can use o-ring sealed G3/8 (3/8" BSPP) fittings in parts tapped for 3/8" NPT provided that the threaded portion of the fitting is somewhat short. The older Swiftech radiators are a good example of a part which will accept G3/8 barbs without issue. #8 · Feb 10, 2023 I want to know about G letter mining. #9 · Feb 10, 2023 The big difference is the pitch of the threads. NPT is angled pretty steep, so that it tightens up as you thread it in. And as mentioned by others, G1/4 is sealed not by the threads but with an O ring. The downside to NPT is it doesn't really work for a 100% airtight seal without using a fair amount of tape on the threads. And because of how it works the threaded ends need to be longer. It would make our fittings way too long to be practical for use in tight quarters. And as far as I know the G designation is just a watercooling thing, it's actually BSPT (British standard pipe thread). If you go looking for an adapter at a standard hardware store that's what you want to ask for, BSPT 1/4 to NPT. I discovered that when making my own pressure tester. This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread. Insert Quotes Post Reply

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