How to CORRECTLY install a shower head?

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My shower head is leaking at the connection to the shower arm.
Whenever I screw on the shower head and tighten, the rubber washer that was included with the shower head (and most other washers that I tried to use instead) get pushed into the shower arm pipe, rendering it useless!
Adding plenty of Teflon tape reduces the leak, but does not completely stop it.

My question is two-fold:

1. What is the proper way of installing a shower head? I am confused because elsewhere in pluming, to my knowledge, fittings that require a washer normally don't need thread sealant as the watertight seal is made by the compression against the washer (however my understanding was that the threads in compression fittings are not tapered NPT but untapered - e.g. stop valves, garden hose). In most videos, many of them by amateurs, they use Teflon tape. However I read two comments from pros on other threads in this forum who DON'T use Teflon tape for shower heads. I am confused by all of this and by the fact that shower heads have NPT threads AND come with washers - which of the two is supposed to make the seal?

2. Why does the washer "disappear" into the shower arm, rendering the washer useless? The shower arm appears to be a garden variety from a big box store. The shower head manufacturer reassured me that the shower head nut and the washer are manufacturerd to standard U.S. specs. Do I need to get a new shower arm?
 
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Jadnashua

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Most shower arms and showerheads sold in the USA (but not all) use tapered pipe thread and to seal do require either tape or pipe dope or they'll leak. If you have a standard arm and the showerhead came with straight threads, you need an adapter to make it all work together. Tapered threads lock together, squeezing the tape or are filled with pipe dope to make the seal...straight thread cannot be reliably filled in this way to make a seal, they require the gasket at the end and a square shouldered area to bottom against and make the seal. A typical shower arm does not have that stepped, flat bottom to hold the washer/gasket to make a seal.
 
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Most shower arms and showerheads sold in the USA (but not all) use tapered pipe thread and to seal do require either tape or pipe dope or they'll leak. If you have a standard arm and the showerhead came with straight threads, you need an adapter to make it all work together. Tapered threads lock together, squeezing the tape or are filled with pipe dope to make the seal...straight thread cannot be reliably filled in this way to make a seal, they require the gasket at the end and a square shouldered area to bottom against and make the seal. A typical shower arm does not have that stepped, flat bottom to hold the washer/gasket to make a seal.

Thanks, and point well taken, but it does not explain the conundrum in my original question. If your statement "most shower arms and shower heads..." is correct, and given the statement by the manufacturer that the head and washer are manufactured to "U.S. specs" (which I then assume implies it is tapered), it begs the question what is the purpose of the washer. If your other statement "a typical shower arm does not have that stepped, flat bottom to hold the washer..." is correct, I would conclude that it can be expected that the washer gets pushed into the shower arm. However, the manufacturer advised not to remove the washer. My original two questions are still open.

Thinking a little more about it, I have a hard time understanding the concept of having NPT threads with thread sealant AND a washer. Either the end of the shower arm pushes hard against the washer for a watertight compression connection, in which case it would be impossible to apply the correct number of revolutions to make a watertight connection with the threads. Or we seal via the NPT threads, in which case it would be impossible (or pure coincidence) to create a compression connection via the washer. I would think it is impossible to engineer both "systems" to work simultaneously. Still confused.
 
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Terry

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If the washer isn't helping, remove it and wrap at least three rounds of tape on the threads.
It's a tapered thread on the arm.
If that fails, buy new stuff. It should work though.
Most of the time, the washers work. You can't tightent them too tight though.
 

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Maybe try and use a little vaseline on the washer to keep it from binding and be sure you are not overtightening. With a rubber washer it shouldn't take much force. Hand tightening is even sometimes enough. With a rubber washer there shouldn't be any need for tape or dope if all is well. I assume you tried a new rubber washer?
 

Jadnashua

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If your showerhead came with a washer to seal it, it is not designed for a typical shower arm. It will only seal to one that is designed to seal like that of a hose using the supplied gasket. Your choice is to either change the shower arm to one that will work with it, or buy an adapter, which may be hard to find. You can't connect NPS thread to NPT without an adapter - you will not get it to seal. The first is 'straight' thread (needing a gasket) and the second is 'tapered' meaning that it needs a sealant to make it water-tight. It sounds like your showerhead is NPS, and your shower arm is NPT
 
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If the washer isn't helping, remove it and wrap at least three rounds of tape on the threads.
It's a tapered thread on the arm.
If that fails, buy new stuff. It should work though.
Most of the time, the washers work. You can't tightent them too tight though.

Thanks. Threads with tape alone don't fully seal, as the situation with washer pushed into the shower arm already simulated a "threads only" attempt to seal as if no washer was there. Didn't fully stop the leak. I'm not a pro, but did a lot of plumbing (other than shower heads) and pretty sure I used the Teflon tape and screwed it on right.
 
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Maybe try and use a little vaseline on the washer to keep it from binding and be sure you are not overtightening. With a rubber washer it shouldn't take much force. Hand tightening is even sometimes enough. With a rubber washer there shouldn't be any need for tape or dope if all is well. I assume you tried a new rubber washer?
Thanks. I sent the unit back to the manufacturer and they returned it with a new washer inserted and advised against removing it or replacing it with a different washer, and reassured that shower head nut and washer are precisely manufactured to standard U.S. specs.
However it appears that the tube wall of the shower arm is so thin that the washer gets pushed into the arm instead of the arm pushing against the washer.
 
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advised against removing it or replacing it with a different washer, and reassured that shower head nut and washer are precisely manufactured to standard U.S. specs.
However it appears that the tube wall of the shower arm is so thin that the washer gets pushed into the arm instead of the arm pushing against the washer.
You need to pay attention to the advice you are getting here, they are all correct solutions.

If you insist on using your product, make the necessary changes per the replies you got. Or, change your old "shower arm" to one "precisely manufactured to standard U.S. specs".
 
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If your showerhead came with a washer to seal it, it is not designed for a typical shower arm. It will only seal to one that is designed to seal like that of a hose using the supplied gasket.
You are speaking my mind. Thanks for confirming my understanding.

Your choice is to either change the shower arm to one that will work with it, or buy an adapter, which may be hard to find. You can't connect NPS thread to NPT without an adapter - you will not get it to seal. The first is 'straight' thread (needing a gasket) and the second is 'tapered' meaning that it needs a sealant to make it water-tight. It sounds like your showerhead is NPS, and your shower arm is NPT

Thanks. But are you sure that there are two types of shower arms and shower heads (NPS and NPT)? All shower arms at the orange big box store appear to have either NPT in their spec, or are silent, which I assume means NPT. All shower heads that I checked are silent on their thread specification. If there were two incompatible systems, I think it would be specified. However, I came across another article that says "Some shower heads come with a rubber washer that you must install. If your shower head did not come with a washer, skip this step. If it did come with a rubber washer, insert it into the shower arm connection nut, and push it down flat."
Furthermore, I found another opinion piece on another plumbing forum saying "Most modern heads come with a flow restrictor/washer that seals to the arm and TPRE tape is usually ineffective to seal it because the threads are made intentionally "loose" so the arm WILL push against the washer."

Do the professional plumbers here on terrylove agree with this?

In summary, my interim conclusion is that all standard shower arms and heads in the U.S. have NPT threads, BUT whether the seal is actually made with the NPT threads or the washer depends on the manufacturer and on whether a washer was originally supplied with the shower head kit.

We got 2 conflicting suggestions in this thread alone (washer with no thread tape vs. thread tape with no washer), which are then probably both right depending on which type of shower head it is. I am surprised that such a simple DIY task can be so confusing.

I also conclude that in the case where the shower head contains a washer, the end of the NPT threaded shower arm has to have some minimal wall thickness to prevent the washer from being pushed into the shower arm. Does that make sense? If yes, I will try to find a higher quality shower arm with maybe slightly thicker wall that works better with that shower head... maybe a Delta shower arm vs. Glacier Bay, what do you guys think?
 
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Jadnashua

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What shower head came off of the arm originally? Some of them are sold as a set - showerhead and shower arm, but the vast majority rely on NPT and do require tape or pipe dope to create the seal. While they may fit together, NPS and NPT threads are not interchangeable, as far as I know. Throw in that many of the stuff we buy is made in China, and even if it should meet a standard is not a guarantee as it costs money to keep the tools sharp and do it correctly. You get what you pay for in many cases.
 
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What shower head came off of the arm originally? Some of them are sold as a set - showerhead and shower arm, but the vast majority rely on NPT and do require tape or pipe dope to create the seal. While they may fit together, NPS and NPT threads are not interchangeable, as far as I know. Throw in that many of the stuff we buy is made in China, and even if it should meet a standard is not a guarantee as it costs money to keep the tools sharp and do it correctly. You get what you pay for in many cases.
thanks but I have yet to see an NPS shower arm or head. The current shower arm came with the house, but I have a feeling it may be the one from "Glacier Bay" from the orange store. I see you are an engineer and probably you are correct from a theoretical point of view, but practically all arms and heads seem to have NPT so they are "almost compatible", just how the seal is actually made (threads vs. washer) depends on the manufacturer. I am still surprised how much confusion this seems to create. Unless someone proves me wrong, and/or has a better idea on how to proceed with the problem, I currently stick with my theory in my last post.

I am deliberating if I should just get another Glacier Bay shower arm for $7.34 hoping it is more precisely cut or has a thicker wall than my current sample, or with the Delta at $40+. My shower head is neither Glacier Bay nor Delta. Do Delta shower heads come with a washer? If yes, I would hope that the Delta shower arm would work better for a washer/compression seal. Opinions?
 
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thanks but I have yet to see an NPS shower arm or head. The current shower arm came with the house, but I have a feeling it may be the one from "Glacier Bay" from the orange store. I see you are an engineer and probably you are correct from a theoretical point of view, but practically all arms and heads seem to have NPT so they are "almost compatible", just how the seal is actually made (threads vs. washer) depends on the manufacturer. I am still surprised how much confusion this seems to create. Unless someone proves me wrong, and/or has a better idea on how to proceed with the problem, I currently stick with my theory in my last post.

I am deliberating if I should just get another Glacier Bay shower arm for $7.34 hoping it is more precisely cut or has a thicker wall than my current sample, or with the Delta at $40+. My shower head is neither Glacier Bay nor Delta. Do Delta shower heads come with a washer? If yes, I would hope that the Delta shower arm would work better for a washer/compression seal. Opinions?

i would think any new arm would work just fine. I try and stay away from the cheap stuff tho. Replace the arm and you should be good to go. Take the old one with you and compare wall thickness of the new. Depending on the age of the old one it could sbow some signs of wear. It's amazing what moving water can do to metal over time.
 

Jadnashua

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A male NPS really requires a moderately thick mating surface for the washer/gasket, otherwise, it tends to just cut into it or push it aside. Look at your hose bib or washing machine connections...they are not thin pipe with threads on them....they have some substance. While you may get lucky if the showerhead is NPS threads on a NPT male pipe, it is not guaranteed to seal properly.
 
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A male NPS really requires a moderately thick mating surface for the washer/gasket, otherwise, it tends to just cut into it or push it aside. Look at your hose bib or washing machine connections...they are not thin pipe with threads on them....they have some substance. While you may get lucky if the showerhead is NPS threads on a NPT male pipe, it is not guaranteed to seal properly.
Thanks, no offense, but I still believe all shower heads are NPT, unless someone provides a trustworthy citation that says the opposite, or at least one shower head currently available in the U.S. that has non tapered threads. I cannot image tapered and non-tapered threads screwed together without breaking something. That would be too odd of a hack. My current theory is still that the problem lies in the unspecified wall thickness that can make certain shower arms incompatible with certain washers or washer/head combinations. Since the shower heads specs don't usually specify the thread type nor compatible shower arms but rather rely on the threaded end of tapered threads to push against a washer for a compression seal, installing a shower head appears to be like gambling - somehow it works in most cases, but not always, and most layman and some pros are unclear whether it's a compression or thread seal for a particular shower head, and attempt to do either one or both simultaneously just to have a warm fuzzy feeling?! - I'm out trying to replace a 1/2" NPT with a 1/2" NPT shower arm, trial and error, and only an astrologist may be able to tell whether it's compatible with my shower head?! crazy!
 
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For those who are interested: No leaks after replacing the shower arm with a Glacier Bay :) Also, as expected after the above discussion, NO thread sealant needed between shower head and shower arm!
P.S.: Replacing a shower arm is the easiest DIY job ever. The old arm needed 3 turns counterclockwise to remove, and I did 3 turns clockwise by hand to install the new one, using the 45 degree angle of the shower arm to gain a little bit of leverage. No leak behind the wall. Not sure why this needs less turns (and only hand tightening) to be waterproof than many threaded brass fittings that I've done before. Not sure if more turns would be preferable. I just mimicked the old installation, hoping the latter was done professionally.
 
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Terry

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I was handed a Rohl shower arm the other day that came with very short and straight threads. I was supposed to mate that with a standard shower head.
We wound up getting a different shower arm for it.
 

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Not sure why this needs less turns (and only hand tightening) to be waterproof than many threaded brass fittings that I've done before.
Unless the shower head has a cutoff, the shower arm never sees high pressure.
 
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Unless the shower head has a cutoff, the shower arm never sees high pressure.

Do you have any evidence for this? Not that it relates a lot to the subject of this thread, but I believe the water in the shower arm is under a pressure almost equal to the house water pressure, as only 1/2" pipe (or larger) is between the house main water pipe and the shower arm, which would normally have minimal pressure drop. I was under the impression that most of the pressure drop occurs at the shower head aerator and within the shower head. Granted, I don't know what is the fluid dynamics and pressure drop within the mixing valve.
 

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I was under the impression that most of the pressure drop occurs at the shower head aerator and within the shower head.
I forgot about the flow restrictor in most shower heads sold today, so I was wrong. Your analysis looks good to me.
 
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