1/4" NPT fittings not matching...


Old 09-22-19, 01:30 AM
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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

This quick release with 1/4 NPT male does not fit the ballvalve.

This male to male 1/4 NPT TO M22 does not fit the 1/4" ballvalve.

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

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."

"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 "
Old 09-22-19, 05:27 AM
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First, I would never put a ball valve on the output of a pressure washer. When running pressure washer must have water flowing through the pump to keep it cool. For changing from the hand gun to a long wand I would turn the machine off.
Old 09-23-19, 02:16 AM
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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.
Old 09-23-19, 12:05 PM
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And the threads may be oddball just to keep someone from doing something that could damage the unit.
Old 09-25-19, 07:31 PM
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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?

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?

BTW, it's perfectly safe to put a ballvalve on even a consumer grade washer. It's actually quicker and safer than walking over and turning off the machine and water (or just kinking the hose in between changing guns).

DO NOT stop spraying water for more than two minutes at a time. Pump operates in bypass mode when spray gun trigger is not pressed. If pump is left in bypass mode for more than two minutes internal components of the pump can be

^ from manual
Yes it's optimal to ALWAYS be spraying and never let off the trigger but now and then and under 2 mins is ok.
Some good sort of tricks to keep a powerwasher running good is using protector/winterizer pump product more often than just to winterize it from prevent freezing damage. It's also a protector.
Also good to let the machine cool down now and then. Many people runs these for hours on end, the pump does have a temperature release but is probably better to let it cool down now and then.

Last edited by gunner666; 09-25-19 at 08:34 PM.
Old 09-26-19, 05:50 AM
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"...there is a tad of wiggle though..." That is not a good sign. Either you are mixing different kinds of threads or you have stripped out the fitting. Either way NPT fittings are designed to seal with the very tight seal between threads. Any wiggle is unacceptable. At best it will leak, worse the fitting can go shooting out like a bullet when pressure is put behind it.

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