Feeling A Bit Nipply?

[sudsmaster]

The plumbing variety, that is...

The cold water pipe under the kitchen sink has been leaking for a while. I had to replace the valve a few years ago and noticed that the nipple - which is the short pipe threaded on both ends - had rusted away to the point where only a few threads were engaging. Periodically I'd tighten it up if it showed signs of leakage. But last night as I was installing a new under-sink wastebasket-on-roller-bearings, I noticed it was leaking again. I tightened it up some more until no more threads were showing. This morning I saw more drips on the paoper I put down to monitor it, and decided enough was enough. I have a supply of nipples of various sizes, so didn't even have to visit the hardware store. However I was a bit worried that the old nipple would be frozen and that trying to remove it would cause a leak behind the wall. I'd tried to remove it before but the pipe wrench I had was a bit too big and it couldn't get a good grip on it, the nipple being fairly short without a lot of area to grab. But I got a new set of pipe wrenches (isn't Harbor Freight great?) and a new shorty wrench fit just right. A few strong pulls on the wrench eventually freed the old nipple.

Good thing, too. When I inspected it, I noticed that the threads that I thought were still there were rusted to the point where you could see light through them. There was only one good thread left... and there should be a minimum of three.

Here's a shot of the old and new nipples. As you can see I put back in a longer one so it won't be so hard to replace next time. I figure that's gonna happen eventually because the valve is brass based, which will tend to corrode the galvanized steel fitting over time. But hopefully by that time I will have replaced all the pipes below with copper.

 

[sudsmaster]

And here's a shot of where the nipple goes. As you can see it's a kind of tight fit. I was glad when it was over.

 

[rp2813]

Hey Rich,

Glad you got this done without the snowball effect you were concerned about. My dad always said you need the right tool for the job, which you will see for yourself soon enough.

Ralph

 

[sudsmaster]

Old time machinists made all their own tools. That's what Walter Chrysler did when he went to work for the railroad - made every tool in his toolbox. Nowadays we just buy them, many from China. It will be nice to see some good old fashioned made-in-USA tools for a change ;-). I made some tools in my shop classes, some of which I use on a regular basis. But not a micrometer as I understand old time machinists used to make for themselves.

 

[panthera]

I'm still using

most of the Craftsman tools my parents gave me as a teenager. OK, some of the electrical tools have bit the dust, but the quality of US made tools was great. Still is, actually - just, the only stuff I know of still made in the USA is the high-end professional/engineering grade.
Glad you got it out in one piece!

 

[sudsmaster]

Plumbing Quiz

OK, I forgot how much Rector-Seal stinks (now that I'm using an undersink garbage bin, I can smell the pipe dope).

Question for the masses (it's a quiz, I know the answer):

What is the purpose of pipe joint compound, also known as pipe dope, or teflon tape?

a) To prevent corrosion
b) To lubricate the threads
c) To seal the threads

I'll give the answer after a few of you have answered...

 

[jeffg]

d) All of the above?

 

[rp2813]

If not all, then at least A & B.

My dad did make a lot of tools but it seems he got his hands on a few pre-made micrometers and didn't need to make his own.

 

[sudsmaster]

We need one more contestant

And then I'll give you my answer.

 

[sudsmaster]

OK, I give

The correct answer is (b), the primary purpose of pipe joint compound is to lubricate the threads.

A pipe thread is done on a taper, with a matching taper on the other piece. The join seals by metal-metal contact. The threads are also "sharp-V" in profile, which means that the peaks and the valleys will mate exactly at some point in the taper. The threads may not be precisely cut and therefore some torque is necessary for full engagement and possibly also some deformation of the threads. If the threads are dry, any burrs or surface irregularities may interfere with proper torquing and result in a leaky joint. For a similar reason it's usually recommended to lubricate straight threads that must be torqued to a certain setting, as on an automobile, so that the proper tightening is applied.

Without proper lubrication, the threads may not engage fully and adequate umetal-metal contact may not be achieved. Pipe joint compound is a mixture of oil and a kind of clay base (which helps to keep it from running). Teflon tape by itself is a good thread lubricant. When tightening a new pipe joint, you may be able to feel when the sliding stops and the metal suddenly starts to engage. This is a very strong seal and can stand up to a lot of pressure - something that pipe dope and teflon tape alone couldn't handle. It also helps to explain why non-leaking pipe joints can be so difficult to undo. Well, that, and the inevitable rusting of steel pipe joints (there is no galvanizing on the threads, usually, and pipe joint compound probably won't protect internally exposed internal threads. Plus, teflon tape can help to make a great pipe joint but it has even less ability to resist corrosion than pipe dope. Residual pipe joint compound or teflon tape however may help with joint disassembly later on.

 

[toggleswitch2]

Interesting. In the old days, pipe dope was used with string. Ostensibly, the string was the sealant. Today, teflon tape serves as both.

 

[sudsmaster]

As an example of the nature of a pipe joint, there is a precision version called the dry-fit pipe joint. The male and female threads match so closely that no lubricant (or sealant, if you will) is needed for complete metal-metal contact sealing off the labryinth created by the threads. These types of pipe joints are used in clean applications where a pipe dope would contaminate whatever is being piped.

I have seen references to string pipe sealants, impregnated no doubt with some sort of lube. However if you thing about how a pipe joint works, in all liklihood the string is pushed back from the tip of the male pipe where the metal-metal contact with the female bore will happen first.

I suppose in low quality threaded pipe pieces, where the threads are poorly shaped, and sufficient torque for ensuring metal-metal contact is not possible, in a low pressure application (like a drain line) a string or other type of "sealant" could indeed take on the role of preventing leakage.

The main problem with pipe threaded joints is that if the pipes are subjected to movement, there is a chance that the joint will unscrew, lose it's metal-metal contac, and stop sealing. For such pipe joints there are special "sealants" which in fact are a type of crazy glue to help prevent the joint from unscrewing. But again, the sealant's role is not to seal, but rather to lock the pipe joint in position so it doesn't unscrew and leak.

 

[rp2813]

Low Quality

When I was installing our outdoor shower out back, I could only find pipe and fittings that were made in China. Even with teflon tape it was leak-prone. These materials came from my handy ACE Hardware, the one with the chunky hunky but not quite as helpful as I wish he'd be ;-) hardware man. I checked at Orchard Supply and found Chinese pipe and fittings there too. I didn't even bother with HD as I'm sure it's all Chinese all the time there. The stash of this type of stuff in my dad's old shop has dwindled to the point where I have to buy certain pieces and I'm wondering where I can find made in USA pipe these days. Or did I just get some bad pieces and Chinese stuff is generally OK? I'd still rather not dump any more money into the Chinese economy though.

 

[sudsmaster]

Ralph,

Was this steel pipe or brass fittings, or both?

If you're handy you can pick up a set of pipe thread dies at Harbor Freight relatively cheap, and use those to thread the ends of pipe. The taps are a bit more expensive, though.

I haven't had a problem with getting standard storebought pipe fittings to seal. Are you applying enough torque to get to the metal-metal contact?

I have had issues with Chinese made air compressor filter fittings. These were chrome plated and simply threaded incorrectly, so that they would bottom out before sealing. I would routinely replace them with brass pieces (also made in China) and those have worked satisfactorily.

Personally I think teflon tape is a bit overrated. It's great for stuff like drinking water lines, where one may not want to have any chance of a dope type sealant getting in there. But I think a good pipe dope like Rector Seal is easier to apply evenly and often does a better job of lubricating the threads. It just seems to make it easier to detect the point where the two pieces are doing metal-metal. PS-Rector Seal seems to be the stuff that plumbers use and recommend.

I think brass is easier to get to seal because it's softer than steel, and therefore deforms under less torque. This deformation can be critical to a good metal seal.

 

[rp2813]

Rich, it was galvanized pipe. There's some pipe threading equipment and dies in my dad's old shop but I doubt I'll ever get that energetic with my plumbing jobs so it will probably be up for grabs at the estate sale next week.