NPT vs MIP?

darkzero

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I've searched & searched but can't find a definitive answer. Does anyone know what the differences are between NPT & MIP thread? Many say they are equivelent but the 1/2" MIP fitting I got does not seem to fit a part that I have correctly which uses 1/2" NPT. The MIP fitting does not seem to have a taper or taper enough to "seal".

When did they change over to MIP? I remember when I used to mess with a lot of fittings & NPT was very common. Every hardware store I went to has no trace of NPT & it's all MIP & FIP.

Hmm, or maybe it's just my part? :thinking:

I'm going to purchase the fittings online but I'm still curious.
 

unterhausen

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I had never heard of MIP, but everyone online says they are compatible. One thing is that pipe threads don't actually ever seal. I use the loctite pipe thread sealant instead of teflon tape.

Parker isn't allowing me to download their catalogs, I was just thinking I needed a new fittings vendor...

I just looked in the MSC catalog, they still talk about NPT fittings. If I needed something like that for anything more than plumbing, I'd go with MSC and Parker. Unless there was a Parker store nearby.
 

OCD

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I had never heard of MIP, but everyone online says they are compatible. One thing is that pipe threads don't actually ever seal.

I have never heard of them either and deal with various hydraulics systems on the equipment we build at work. We have all but quit using pipe fittings because of leak issues. We use JIC and SAE o-ring fittings when ever possible.
 

darkzero

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Thanks. The references I've looked at has that similar info. The fittings I bought didn't really seem to have a significant taper. Normally I can easily see the taper by eye but the MIP fittings I had didn't really seem to have a noticeable taper, I had to put it against a straight edge to see the taper. I had my part with me & no calipers, I returned them before heading home after checking that they did not fit my part.

One thing is that pipe threads don't actually ever seal.

Yes, the taper alone won't do the job I would be using teflon tape or maybe RTV for this application. But the MIP fittings screwed all the way into my part without ever getting tight from the taper as I'm used to. :shrug:

Was just about to order from Mcmaster but I just found some on ebay for 1/3 of the cost of what I paid for the MIP fittings locally. Mcmaster still references as NPT.

Maybe it's just that particlar brand name that chooses not to use NPT terminology? I went to OSH, Lowes, & Home Depot, they all had the same stock which was from Watts.

I would have like to just use AN fittings but I don't want to spend that kind of money changing everything.
 

unterhausen

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I have never heard of them either and deal with various hydraulics systems on the equipment we build at work. We have all but quit using pipe fittings because of leak issues. We use JIC and SAE o-ring fittings when ever possible.
I have some hydraulic powered equipment that is too valuable to replace, but unfortunately uses pipe fittings. I hate getting hydraulic oil on my hands, and I hate pipe fittings. The loctite sealant is great, you just crank on the fitting a reasonable amount, wait for the sealant to harden, and it almost never leaks.



The fittings I bought didn't really seem to have a significant taper. Normally I can easily see the taper by eye but the MIP fittings I had didn't really seem to have a noticeable taper, I had to put it against a straight edge to see the taper. I had my part with me & no calipers, I returned them before heading home after checking that they did not fit my part.
That's pretty strange, but some of the pipe fittings I've been getting from the BORG seem to have very little taper, but work in plumbing applications. I think they all just fake it and expect you to use a lot of teflon tape and brute force.
 
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darkzero

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That's pretty strange, but some of the pipe fittings I've been getting from the BORG seem to have very little taper, but work in plumbing applications. I think they all just fake it and expect you to use a lot of teflon tape and brute force.

:laughing:

That's part of my issue now, one end has slow leaks, teflon tape. When I went to try & tighten one of them I was surpised at how much more I was able to tighten it but it's still leaking. I'm starting to think it has a MIP fitting on it now with half a roll of teflon tape that has started to deterioate.

It would probably seal if I used RTV but I'm not comforatble with how loose it is & I shouldn't have to use RTV.

However, when I went to return the MIPs, I played with MIP & FIP & they tightened up just fine.
 

65535

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Hey Will, I'm guessing you're setting up some pneumatic piping. I recommend the yellow double thickness teflon tape. In my experience it has been many magnitudes more reliable than the standard thickness pipe tape.

AFAIK the yellow is rated for gas lines (natural, propane, and compressed air) and is just much more reliable. The white tape imo is crap.

Mind you the yellow is a fair bit more expensive. I just stick to NPT fittings, and never have had an issue with yellow tape.
 

darkzero

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Thanks David, I'll use the yellow.

Well I guess NPT & MIP are equivelent. I went to another DIY chain in the next county over & picked up some different brand MIP fittings. They fit good.
 

Achilles

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NPT (National Pipe Thread) and MIP (Male Iron Pipe) threads are generally considered equivalent, with both conforming to the same standards. NPT threads are tapered, designed to seal tightly with the application of torque and a thread sealant like PTFE tape. They are commonly used in plumbing and industrial applications for creating pressure-tight seals.

MIP is a term often used interchangeably with NPT, referring to male threaded fittings that match NPT standards. The confusion may arise from subtle differences in manufacturing tolerances or quality control. If your 1/2" MIP fitting doesn't seem to fit a 1/2" NPT part, it could be due to a specific defect or variation in the part you have.

It's unlikely that there has been a wholesale change from NPT to MIP; both terms still refer to the same threading standards. Ensure both parts are clean and undamaged, and use a suitable thread sealant for the best fit.
More details: https://www.wowowfaucet.com/mip-vs-npt-thread/
 
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