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Old 09-22-2019, 03:30 AM   #1
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1/4" NPT fittings not matching...


I'm putting together a quick release shutoff for a powerwasher to change between regular gun/surface attachment/telescopic extension pole.

It's a 3000psi consumer grade type.

The 3000psi 1/4" NPT ballvalve I bought linked below is commonly used by powerwash professionals I have seen many videos where they use this ballvalve for lower GPM washing like using pressurized water only instead of soap aka soft washing with higher GPM.


the threads don't match up, they screw about 1/4 of the way and seem correct but then they bind up. I took the parts to Lowe's to use the thread checker in the plumbing section (not the nuts and bolts thread checker)

The ballvalve says 1/4 NPT right on it
https://www.ebay.com/itm/High-pressu...75.c100623.m-1


This quick release with 1/4 NPT male does not fit the ballvalve.
https://www.ebay.com/itm/1-4-Male-MN...72.m2749.l2649

This male to male 1/4 NPT TO M22 does not fit the 1/4" ballvalve.
https://www.ebay.com/itm/Pressure-Wa...72.m2749.l2649


Lowe's thread checker =
ballvalve fits 1/4 PULG. MIP doesn't fit ballvalve.
Male to male 1/4 NPT TO M22 coupling doesn't fit pulg.
coupling might be mip.

I think the ballvavle might be the odd ball, and I think my only other option might be the big bulky 7000psi range ballvalves like this which I wanted to avoid
https://www.ebay.com/itm/1-4-High-Pr...kAAOSwjVVVyPql



what am I missing here? they are all sold as "1/4 NPT".

I asked the seller of the male to male 1/4 NPT TO M22 this:
"you sure this is 1/4 NPT? I tried screwing it into a coupling I just bought which has "1/4 NPT" branded on it and it seems as though this wants to cross thread."

Replied:
"It's 1/4 "- 3/8 and 1/2" are huge compared. I was in the machine shop industry programming 1/4" npt threads for years.. maybe the coupler is bad. Check it out and let me know what you think . I will trust your judgment on if it needs replaced with a different one.
Thanks "
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Old 09-22-2019, 06:39 AM   #2
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Re: 1/4" NPT fittings not matching...


Quote:
Originally Posted by gunner66 View Post
This male to male 1/4 NPT TO M22 does not fit ...
M22 is a metric size and is NOT NPT
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Old 09-22-2019, 07:36 AM   #3
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Re: 1/4" NPT fittings not matching...


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Originally Posted by gunner66 View Post
the threads don't match up, they screw about 1/4 of the way and seem correct but then they bind up.
The threads are tapered, so none of the samples you tried screw in all the way, right ? "1/4 of the way" is a poor choice for measurement -- a distance in inches or a number of turns would convey some information. And the distance engaged will be different if you are screwing them by hand or with wrench.

If they are indeed NPT, could be that one or more pieces are out of tolerance. If I were planning on putting 3000 psi through a fitting, I would really want to make sure of having good engagement.

Note that NPT will not be watertight without putting sealant on the threads.
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Old 09-23-2019, 12:06 PM   #4
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Re: 1/4" NPT fittings not matching...


Indeed, a sealant should be used. (ie teflon or the like.) tappered fittings often occur engage to about the 1/4 of the way by hand only. It depends on the tolerances.

(I'm assuming you mean 1/4 if the total threads, vs 1/4 of a single thread.)

Cheers!
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Old 09-25-2019, 10:36 PM   #5
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Re: 1/4" NPT fittings not matching...


The M22 side has nothing to to with the NPT side, sorry confusing.

Also sorry confusing, what I meant by: "the threads don't match up, they screw about 1/4 of the way and seem correct but then they bind up."
^ What I meant is the threads screw in about a quarter of their total length (they only screw in about 1/8" because the threaded portion is 1/2" long). And then they bind up by hand or light wrenching.

"tappered fittings often occur engage to about the 1/4 of the way by hand only. It depends on the tolerances."

^ I did kind of wrench it already..

EDIT/UPDATE: Hopefully solved.

I really had to wrench them down just now but I got them to screw in correctly and with minimal stripping/shavings that I can see, there is a tad of wiggle though but we'll see what teflon does. I won't know until I run the washer if it'll leak but I'm hoping it's solved although I've never come across something like this before with thousands of nuts and bolts -

I've never really dealt with NPT though some maybe these are two SLIGHTLY different pitches? Or an error on the ballvalve?


It's the coupling that's the odd one and not the same type of 1/4 NPT pitch.
The fittings are all the same. I originally thought the male to male 1/4 npt (to) M22 was incorrect because I had only received those 2 items at the time and the ballvalve says 1/4 NPT right on it. (the one I linked just says NPT but mine is the same one and fully says 1/4 NPT, there's others with no branding of NPT).

"NPT (National Pipe Thread tapered), NPTF (National Pipe Thread Fuel) and NPS (National Pipe Straight) threads have the same pitch, look similar but won't seal when attempting to use 2 manufactured from different standards. Your situation wouldn't be the first time something got marked/labeled incorrectly."

Hopefully worst case scenario is these quick connect M22 fittings will fit the larger but bulkier and overkill for 3000psi ballvalves. And I'd probably return this ballvalve as not as described?
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Old 09-26-2019, 08:11 AM   #6
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Re: 1/4" NPT fittings not matching...


Quote:
Originally Posted by gunner66 View Post
.... I got them to screw in correctly and with minimal stripping/shavings that I can see, there is a tad of wiggle.....
Something not right. Should be zero stripping, zero shavings, zero wiggle.
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Old 09-26-2019, 10:04 AM   #7
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Re: 1/4" NPT fittings not matching...


My PW has a 3/8 pipe thread 7200 PSI ball valve as a drain. The hoses, guns, quick connectors, reels & wands are 3/8 pipe thread, 3500 PSI. Go to the closest seller of commercial quality PW stuff. They sell to the guys who make a living using their PW. If you cannot find one locally, a rental agency might be able to help you.

Or look in the yellow pages under "Commercial Hood Cleaners". Ask where they get there stuff. Good hood cleaners cannot afford to have their equipment fail at 2:00 AM,
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