Replies

1. 
   Dave45 | Sep 11, 2006 04:33am | #1

   I generally wrap a couple of layers on at least 75% of the threads.  On new threads it helps prevent galling and on old threads, I like the extra sealing.

1. 
   alfie | Sep 11, 2006 04:43am | #2

   Thanks. I installed a brass nipple in a PVC bushing, and applied 2-plus layers of tape. I had to take the joint apart and was surprised to find I had managed to strip the threads to some extent. It was a hard to reach place, and in this instance I think I started the tape right from the end of the nipple ... and probably managed to skew the fitting. So I was curious what others do. As I recall, I used to leave a couple of threads without tape so that the fitting starts properly, then the tape seals. Been a while, and I was trying to remember the correct way.

1. 
   Dave45 | Sep 11, 2006 04:55am | #3

   Yeah, too much tape can make the theads feel "mushy" and - if you're reaching - they may cross thread.  Leaving a couple of threads "naked" would probably be a good idea.

1. 
   KirkG | Sep 11, 2006 05:17am | #4

   Pipe threads are tapered so the seal doens't really start at the tip. I was always taught 3 wraps minimium. I also always put some yellow Rectorseal on as well. With this process I have never had a leak and can stop tightening when I want to, ie pipes lined up the way I like. I don't have to force the pipe one more time around. It also allows for non locked up joints when I need to disassemble later.

2. 
   moltenmetal | Sep 11, 2006 02:41pm | #5

   Metal to PVC threaded joints are always tough- best to avoid them entirely.  The PVC female fittings aren't strong enough to withstand the forces that an incompressible metal male tapered fitting puts on the joint, and over time the female fittings can tend to split. 

   If you have to do such a joint, a plastic male fitting in a metal female fitting is the better way to go.  And the most effective way to keep it sealed is to use a paste type thread sealant or "dope".  But be careful, because most of these sealants can cause PVC threaded components to crack or soften.  Choose one which says "compatible with plastic fittings" right on the label, or you're taking a big risk of a failure later.

2. 
   WorkshopJon | Sep 11, 2006 05:39pm | #6

   	78535.1
   	"What is the correct technique for applying Teflon tape to a threaded joint in plumbing" Alfie, IMO, depends on the tape you are using, as they come in various thicknesses. With the yellow (often sold as "gas line tape", you can get by with two layers.  The thin white stuff you need more.  not to be confused with the old white, which is the same as the current yellow. WSJ

1. 
   moltenmetal | Sep 11, 2006 06:32pm | #8

   I thought so too, but it turns out that they almost all come in the same thickness- 0.003"- so you can't judge them on thickness. 

   The difference in the weight or "feel" of the "thinner" stuff you find at the hardware store is its density rather than its thickness.  The "thin" stuff can go as low as 0.25 g/cm3, whereas the full density materials (the "yellow" gasfitters's tape, for instance) is 1.3 to 1.5 g/cm3. (BTW, you can still get white full-density teflon tape- Swagelok and 3M both sell it, but others do too and for much less money). 

   The denser stuff does take fewer wraps to leave an adequate layer of sealant in place, but it's a bit harder to apply properly because it's not as compliant- it doesn't naturally sink into the threads of the male fitting as easily.  How many wraps you use is a judgment call/trial and error thing, depending on the size and roughness of the threads and whether or not you're top-dressing with a paste sealant.

1. 
   alfie | Sep 12, 2006 01:45am | #9

   Thanks for all the info above. In particular, the comments on feel, judgment, and trial and error resonates with me. No open and shut answers to most problems.Nobody said life was going to be simple. I decided to install a shop sink. This involved putting in a sink pump (Liberty 403). I got the bright idea that I could discharge the back wash from the water softener in to the same 1-1/2" PVC drainage line, so installed a T (pointing upward) at the appropriate point in the horizontal run. Put in a female bushing, that takes the adapter that goes from hose connection to male thread. Got the sink all set up, supply lines in place, drainage line compete. Run water in sink. Pump bucket fills up, pump kicks in, and water starts to run. Next thing, water is spurting out of the T that was intended for discharging softener back wash in. Immediately apparent that a back flow preventer need there. Supply house set me up with a brass threaded nipple (come to think of it, plastic would have been better) and brass flapper-type check valve. Didn't do the job, still spurting. Perhaps a spring type of back flow preventer might work, but not sure the pressure from the softener discharge would open it. Discovered when removing threaded nipple that bushing threads are stripped, not sure how much. In the end, KISS won. Planning to simply run tubing along the 1-1/2" drainage pipe for softener backwash discharge, thus keeping it simple and altogether avoiding the backflow preventer situation. Meanwhile, could cut the T out and splice in a new section of tube, so I am not reminded of the lousy plumber who stripped the fitting. Or, could jam in a plug, hope it does not leak, and forget about it. Leaning toward the latter!

3. 
   Shacko | Sep 11, 2006 06:13pm | #7

   Most teflon will tell you what the minimum wraps that they recommend for an installation, I always leave one or more threads without tape so it dosen't fine its way into the valve mechanism whether gas or water. One of the other posts also said he uses Rector-Seal on the top of the tape; I agree. Lots of luck. _______________________________________________________________________

   "If you don't have time to do it right, where will you find the time to do it over?"
4. 
   DDay | Sep 12, 2006 04:04am | #10

   Make sure you go clockwise if you are holding the pipe end towards you.  if you put it on the reverse, as you tighten the pipe, you'll be backing the teflon tape off.

5. 
   Mongo | Sep 12, 2006 05:54am | #11

   Only read this if you have insomnia:

   Originally PTFE tape was made in both a single density and double density type. The single density type was typically made in 1/2" x 520" rolls and commonly distributed in all hardware stores.

   Double density PTFE tape was made in 1/2", 3/4" & 1" widths and typically distributed through the Plumbing, HVAC and Mill Supply stores but rarely found in the hardware.

   Many jurisdictions adopted the double density tape as the standard for sealing threads on natural gas lines. Later, in an effort to insure the double density tape was being used the industry began making the double density in a yellow color to distinguish it from its single density counterpart.

   Recently the ASTM(American Society of Testing & materials) and ANSI(American National Standards Institute) adopted new standards for PTFE tape and instituted a color coding system to identify the different grades.

   White..Single Density -for NPT threads =/< 3/8"
   Yellow..Double Density -for NPT threads >3/8" but =/< 3/4"
   RED... Triple Density -for NPT threads > 3/8" but =/< 2.5"
   Green..Oil Free PTFE tape for use on Oxygen lines
   Gray...Type N for use on stainless steel lines

   Copper..PTFE tape containing copper granules,,used as a thread lubricant but may not be used as a thread sealer.

   PTFE tape is only approved when the proper type is matched to the size of the joint and when three full wraps are applied under tension and wrapped in the direction of the thread.

   While Teflon tape is commonly used by the homeowner and some tradesmen for all thread joints it is best to only use it on "Non-permanent" joints, such as attaching the shower arm, an angle stop or other joints that will require periodically changing out.

   PIPE DOPE is the preferred thread sealant for permanent joints, such as threaded water lines or gas lines, but you must be careful when selecting pipe dope. You must read the labels carefully and be sure the product you select is specifically labelled as suitable for the application that you intend to use it for.

   In the hardware stores we commonly find either the Gray pipe dope or the white "teflon" pipe dope. The white teflon pipe dope has a small advantage because it contains teflon granules that work as a thread lubricant which aids in making tight joints.

   Most tradesmen rely upon Rectorseal which is a nearly universal pipe thread dope which is listed for Potable water, Non-potable water, Steam, Natural Gas, Propane, Gasoline, High pressure Air, Nitrogen, Hydrogen, and most industrial gasses & chemicals.

   While RectorSeal is difficult to find in the hardware or big box stores it can be commonly found in any Plumbing, HVAC or Electrical supply house in sizes ranging from a 4oz can to a gallon bucket.

   Rector seal is made in both a hardening and non-hardening formula. The hardening type is most commonly used on steam piping while the non-hardening type would be most suitable for the typical residential application. The non-hardening type also has the advantage that it will not dry up and get hard in storage.

1. 
   RichBeckman | Sep 12, 2006 11:44pm | #13

   "Only read this if you have insomnia:"When preceding a Mongo post, a sure sign of a great post!
   Rich BeckmanAnother day, another tool.

1. 
   Mongo | Sep 13, 2006 02:34am | #15

   Rich!Long time buddy.Tell the missus I said "hello".Best, Mongo

2. 
   xxPaulCPxx | Sep 13, 2006 01:14am | #14

   Yellow RectorSeal rocks - I got it at HD and used it for my gas lines.  Really sucks to try and get out of shag carpet though... did I mention those handy yellow tubes are easy to step on?Rebuilding my home in Cypress, CA

   Also a CRX fanatic!

1. 
   Mongo | Sep 13, 2006 02:34am | #16

   Oh....painful!

2. 
   migraine | Sep 13, 2006 10:19pm | #22

   Or.... getting it out of your hair when runnings lines in a tight crawlspace

1. 
   xxPaulCPxx | Sep 14, 2006 12:04am | #23

   Oooooo - wicked!  My worst was a quart of dirty motor oil in my hair when it was long... hair made a nice mop for it, I accidentally found out.Rebuilding my home in Cypress, CA

   Also a CRX fanatic!

3. 
   alfie | Sep 13, 2006 03:03am | #17

   Thanks for the great info. I read it shortly after you posted it. Then I went to sleep.

6. 
   plumbbill | Sep 12, 2006 06:30am | #12

   I'm not going to add any about tef tape installation, you allready got a lot of good answers.

   I am going to comment on female pvc threads.

   On a potable water sytem female pvc threads are not aloud according to the UPC.

   On a waste or vent system I try to avoid them as much as possible. To easy to cross thread & fitting splits are quite common even when screwing plastic to plastic.

   "I'm here to chew bubble gum & kick azz, & I'm all out of bubble gum" Rowdy Roddy Piper

1. 
   alfie | Sep 13, 2006 03:03am | #18

   Thanks. Noted.

7. 
   darrel | Sep 13, 2006 05:45am | #19

   I noticed a few mentions of 'gas' tape. When we hooked up our new gas dryer this summer, the instructions for connecting to the drier explicitely stated 'NO TAPE' at all.

   Why is that?

1. 
   plumbbill | Sep 13, 2006 08:28am | #20

   I have seen those type of instructions before.

   Mainly it's a precaution --- they don't want any tape getting clogged into the regulator, which can happen if you run the tape past the end of the male thread."I'm here to chew bubble gum & kick azz, & I'm all out of bubble gum" Rowdy Roddy Piper

2. 
   Shacko | Sep 13, 2006 06:26pm | #21

   A manufactor has certain ideas of how things should be hooked up, when you do this for a living you modify what you have a prob. with, thats where the opinion comes in. If you hooked up a gas dryer with no probs. don't worry about it. FYI when pvc plastic was first put on the market the manufactors said that you didn't need any sealer on thread fittings, that didn't work worth a damm. May luck be with you. ______________________________________________________________________"If you don't have time to do it right, where will you find the time to do it over?"

8. 
   philarenewal | Sep 15, 2006 04:33pm | #24

   >>"What is the correct technique for applying Teflon tape to a threaded joint in plumbing?

   Correct technique (IMHO) is to buy a can of what's pictured, read the label and do as it says.  I've had some bad luck with teflon tape; never had a problem with quality non-setting pipe dope.  Oatey also makes a white pipe dope with teflon that works well.  I find I have need to use it often enough that I keep a small can in my "general use" (almost always with me) tool box.

   View Image

    

   "Let's get crack-a-lackin"  --- Adam Carolla

1. 
   alfie | Sep 15, 2006 05:01pm | #25

   Thanks. I am going to get one of these.

2. 
   IMERC | Sep 15, 2006 05:22pm | #26

   what's yur opinion of blue formula.. 

    

   Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->

   WOW!!! What a Ride!<!----><!---->

   Forget the primal scream, just ROAR!!!

1. 
   philarenewal | Sep 15, 2006 05:30pm | #27

   >>"what's yur opinion of blue formula..

   Never tried it.  I thought it is for locking the threads -- opposite of the end result I want.

   Have you had a chance to try it?

   PS: how it is going -- long time no write (my fault). 

   "Let's get crack-a-lackin"  --- Adam Carolla

1. 
   IMERC | Sep 15, 2006 05:45pm | #28

   it's rated for anti-vibration... it doesn't lock down that I know of..

   been using it for sometime but don't anybody else that is...

   fishing my butt of.. just did all of the NW, Aleautians, Utah and AZ...

   doing the slope the rest of the week....

     

    

   Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->

   WOW!!! What a Ride!<!----><!---->

   Forget the primal scream, just ROAR!!!

1. 
   philarenewal | Sep 15, 2006 05:54pm | #29

   >>"been using it for sometime but don't anybody else that is...

   Sounds good -- I'll pick have to pick up a can and give it a try.

   Sounds like you must be having the time of your life with all that fishing.  Plenty of good vitamins and other good stuff in those fish (I'm assuming some nice salmon).  Tasty too I'll bet.  ;-) 

   "Let's get crack-a-lackin"  --- Adam Carolla

2. 
   IMERC | Sep 16, 2006 12:46am | #30

   if'n it's swimmin'...

   it's fair game... 

    

   Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->

   WOW!!! What a Ride!<!----><!---->

   Forget the primal scream, just ROAR!!!