Practically speaking, as long as the plumbing nipple has tapered threads, properly reamed, and is galvanized it will be Ok.

How it can be determined if it came from the plumbing department or the electrical department would be difficult to prove.

 

Practically speaking, as long as the plumbing nipple has tapered threads, properly reamed, and is galvanized it will be Ok.

How it can be determined if it came from the plumbing department or the electrical department would be difficult to prove.

you can see different in to 2 types of pipe.

 

I think the only argument could be that black pipe isn’t listed in chapter three. So no uses permitted or not permitted. Otherwise they are the same thread. There is no difference between a galvanized plumbing nipple and an electrical nipple. It’s the couplings and hubs that are different

 

344.6 is very clear. Conduit AND fittings must be Listed and Listing carries intended use. This was added to all raceways in 2002. All wiring must use a method in NEC, although not all must be in a raceway: two common examples are type NMB and type MC or AC. When those types are used inside raceways it is a mechanical support.
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Not all hazardous location wiring needs to be GRC with fire blocks. In fact ir can be ANY wiring method with intrinsically safe method.

 

I believe electric threads are tapered while plumbing threads aren't

 

I believe electrical threads on pipe are tapered & the threads inside electrical couplings are not tapered. Someone here, please correct me if I’m wrong.

 

My understanding was the inside of RMC was smooth, so, the wire isn't damaged. Also, does RIGID make separate electrician & plumber thread dies?

 

My understanding was the inside of RMC was smooth, so, the wire isn't damaged.

This is my understanding as well. I was told the inside of rigid electrical pipe has been reamed so that it is smooth. Plumbing rigid is not reamed and can damage wire pulled through it. I'm assuming this applies to nipples and fittings as well.

 

On some female fittings there is a step that is chamfered one the electrical version but not the plumbing version.

At least in PVC the plastic pipe has a UL stamp that is different for electrical use. It’s still schedule 40.

In think you’re thinking if NPST which is straight thread not tapered. Not used in plumbing.

 

I saw this done on a few occasions during my apprenticeship. It's usually the result of p*ss-poor planning or a supposed emergency. Anyway, my journeyman told me to spray the schedule 80 black pipe and the conduit junctions with a flat gray paint (used for touching up panels). From a distance or to the untrained eye, it was hard to see. To be fair, he said if forced to do this, add a ground wire instead of relying of the conduit to serve as ground. Over time, galvanic action will corrode and ultimately break the joint. He wasn't too worried. He knew he'd be in the ground before that happened.

 

If they used galvanized plumbing nipples, There will be no way to tell from the outside. The threads and pipe/conduit are the same. Only differences are on the inside. Electrical conduit nipples are supposed to be smooth with the internal weld removed or smoothed out, both should be reamed. Some brands of RMC nipples have a smooth finish on the outside and some don't. Some have an obvious weld that is somewhat smoothed or removed from protruding and some not so much. On longer nipples RMC will have listing stickers, but not all the time.

They both use the same NPT threads on the nipples. Electrical couplers are not tapered to allow the conduit to thread in further for stronger lateral support, but is not water tight like a plumbing/tapered coupler.

 

I have never liked plumbing in my whole entire life. I, unfortunately, had to experience a multitude of problems related to plumbing during my life, from clogged drains to broken water heater systems. My first time unclogging the drains was a disaster. I didn't know this would be such a big problem until I flooded my bathroom and had to waste a whole day cleaning up and cleaning the drains in order to get the water to go down the drain. A few weeks after that, I had a problem with the water heating system and had to call All Type of Plumbing Services | PS Plumber Singapore and I was really shocked when they fixed it in half an hour.

 

Non issue.
Over thinking if just a close nipple.

Pipe or longer nipples might matter.
Insides of conduit and pipe are different.

Electrical has a smooth interior, plumbing has a weld line.

 

What your referring to is; Chapter 3/ Article 344

344.6 Listing Requirements. RMC, factory elbows and couplings, and associated fittings shall be listed.

Part III Construction Specifications.
344.100 Construction, RMC shall be made of one of the following:

(1) *Steel with protective coatings.
(2) Aluminum
(3) Red brass
(4) Stainless steel.

*I've never seen plumbing pipe w/ protective coating, on inside or the outside of the nipple.

Hope this helps. Have a safe day..

 

What your referring to is; Chapter 3/ Article 344

344.6 Listing Requirements. RMC, factory elbows and couplings, and associated fittings shall be listed.

Part III Construction Specifications.
344.100 Construction, RMC shall be made of one of the following:

(1) *Steel with protective coatings.
(2) Aluminum
(3) Red brass
(4) Stainless steel.

*I've never seen plumbing pipe w/ protective coating, on inside or the outside of the nipple.

Hope this helps. Have a safe day..

The protective coating might be galvanize. I don't know for sure though.

 

The definition of a pipe nipple has a limited length, maybe 24 inches maximum.

People here worrying about difficulties pulling wire thru a plumbing nipple probably are the same ones wearing a mask driving in their car by themselves.

 

Rigid Ferrous Metal Conduit (DYIX) UL Mark ANSI/UL6 is the Listing. (electrical rigid conduit)
Everything has a listing. Refer to the 'white book'.
If NOT listed for electrical, it CANNOT be used for electrical.

 

I know a old post but would like to add a toones worth.

For internal smoothness, I have had electrical nipples with poor reaming and poor finishing internally. I need to build a jig with sand cloth to internally ream the nipple to prevent conductor insulation tearing. So it can work for plumbing nipples or electrical rated nipples.

This is a Segway for the issue of dissimilar metals reacting according to the Galvanic table.

This is a big issue for keeping bonding, if one has not been run separately. Not to mention for threading structure integrity for explosion proof sections.

For a sound installation. The view point of, how the materials react with each other will benefit the installation and your peace of mind.

So if the materials are too far on the Galvanic chart and they are joined. This is a accident waiting to happen. More so in a hazardous area.

The rule of thumb,

Electricians: need the piping to be conductive and leak at a regulated controlled rate. No galvanic action destroying the joints made up tight. with smooth interior walls for ease of conductor pulls

Pipe fitters: need the piping to not leak, but cares of conductive properties if spec on plans, for galvanic mitigation. and also no galvanic action destroying the joints made up tight.

So no matter what trade. Check the internal condition of the piping and prepare as required.

Check threading as well no need to have unnecessary galling because of a bent thread.

 

This simple topic is comically complicated to me

Not for nothing but Ridgid does make different dies for electrical conduit, they make NPSM dies that you'd use rather than the NPT dies you'd use for plumbing. I wouldn't worry too much about causing a hazard using tapered dies.

Tapered male into tapered male you get a lot of mating surface and the seal is going to be very tight, like pressure tight, OK for plumbing, compressed air, etc.

Straight male into straight male you don't get a seal in the threads. (You might get a seal between a shoulder on the male side and the female part, especially with a gasket or sealing washer.) But conduit isn't really supposed to be water tight, right, that's why you have to use THWN in wet locations / underground inside RMC.

Tapered male into straight female you get a limited seal between the threads, it might be weather resistant or drip proof, especially with a sealant, but it or something but it won't seal water or air under pressure.

The real controversy is, is it code compliant to thread a fitting like say an EMT connector into the threads on an LB? 😰

 

This simple topic is comically complicated to me

Not for nothing but Ridgid does make different dies for electrical conduit, they make NPSM dies that you'd use rather than the NPT dies you'd use for plumbing. I wouldn't worry too much about causing a hazard using tapered dies.

Tapered male into tapered male you get a lot of mating surface and the seal is going to be very tight, like pressure tight, OK for plumbing, compressed air, etc.

Straight male into straight male you don't get a seal in the threads. (You might get a seal between a shoulder on the male side and the female part, especially with a gasket or sealing washer.) But conduit isn't really supposed to be water tight, right, that's why you have to use THWN in wet locations / underground inside RMC.

Tapered male into straight female you get a limited seal between the threads, it might be weather resistant or drip proof, especially with a sealant, but it or something but it won't seal water or air under pressure.

The real controversy is, is it code compliant to thread a fitting like say an EMT connector into the threads on an LB? 😰

It has been quite awhile for me to look at a NEC book, so I cannot give you a note for a specific code.

But... yes this is quite the topic.

In Canada.. for the Canadian CEC. Rule 12-1006 states, to reference ANSI/ASME B1.20.1 for threading pipe and fitting joining. The B1 is the code book for the piping trades.

But depending on the classification of the area or conduit service. There are rules that govern threading engagement depth and when straight threads are allowed and not allowed.

An example is 3 complete threads for EMT. But in a Class 1 Division 2. 5 complete thread engagement, and has to be NPT minimum no running threads.

Including a pipe threading chart for all the apprentice's for clarification. with a white paper on threading design.

Also a example of a electrical fitting that uses both.

 

The NEC requires tapered threads but the rigid couplings are not tapered.

My understanding is that for high compression type installs like in thermowells you need the straight threads

 

Maybe I missed it but it took 30 posts before someone quoted the NEC requirements of a taper when cutting and threading in the field. That was a question on one of my licensing tests. 3/4 inch tapered per foot. NEC 344.28

 

 

 

So that makes it clear that NPSC is “straight” tapered threads so just another word for NPT, not NPST despite the name and the screwy way they explain it.

Looks like NPST for electrical, or NPSM is just a myth.

 

I don’t think the threads are the issue with it being considered a bond. It’s the fact that you need two locknuts, or a shoulder and a locknut. So an EMT connector would satisfy the rules for bonding over 250v, but a chase nipple into a coupling or LB wouldn’t.

 

I didn't re-read the original thread, but I thought that electrical conduit was seamed differently so there would be no burrs on the inside of the pipe, plumbing pipe is rougher inside. A lot of plumbing supplies don't stock galvanized steel pipe any more, but I bought some a couple months ago. I wanted to use some pipe just as structural / support material and 1-1/4" galvanized from a plumbing supply I don't have an account with was cheaper than 1-1/4" RMC.

 

Lots of times we need galvanized steel sleeves to put in concrete poured walls before they pour. We normally need 6” sleeves for 4” conduit. There’s a fab shop near us that will sell us the pipe, cut it to lengths specified, and give us the leftover scrap if there is any, cheaper than we can get the pipe from a supply house.

The only thing more expensive is if we have to use the steel sleeves with the water stop.

 

Coming from industrial refrigeration construction (blast coolers/freezers, penthouse units), we found many times that conduit connectors wouldn't thread into LB's, boxes, etc. We used NPS taps on these items to resolve the problem, same thing on motors. Tapered taps wouldn't work but the straight taps saved us time, frustration, and money from junked fittings.