Teflon Tape Vs. Pipe Dope For Sealing Pipe Threads In Plumbing

So, you are working on the plumbing in your house and you know that you need to put some kind of sealer on the pipe threads. Should you use Teflon Tape or Pipe Thread Sealant (Pipe Dope)?

This is a very common question in the DIY Home Improvement Industry! Here is some information to help you make the best decision.

Right Or Wrong?

The honest to goodness truth is that either type of sealer works if used correctly. The problem is in the last part of that sentence! It has to be used correctly!

So as a long-term remodeling professional, this author always prefers to use Pipe Dope. Several years ago they came out with a new type of Pipe Thread Sealant that has Teflon in it. In my opinion, that now gives me the best of both worlds.

However, in the interest of being fair, I have asked several other professional plumbers and remodeling contractors what their opinion is on this subject.

Almost universally, the professionals have responded that they prefer to use Pipe Dope over Teflon Tape to seal the threads on their plumbing projects! That was a pretty good recommendation for me.

Using Pipe Dope The Right Way

Since the most common response was that using either type of product the right way will yield satisfactory results, let's talk about how to use Pipe Dope (Pipe Thread Sealant) correctly.

Pipe dope usually comes in a small tube or in a small plastic bottle with a brush type applicator in it. The old original type of pipe dope was a gray color and was used on both water and gas lines. It is still available in many stores. However the newer type with Teflon in it is, most commonly, white in color. It is also the most common type that you will find in your local hardware store today. It also can be used on both water and gas piping.

The most important thing to know about how to use pipe dope properly is to don't be skimpy with it! You don't need to completely cover the entire thread surface on the pipe as that gets messy from having too much of it left on the outside.

Apply the pipe dope to the male thread surface on the end of the pipe. Make sure that you have at least enough on it to fill 3-4 threads all the way around the pipe. (more on larger diameter pipes) You don't want it on the female threaded side of a joint as that will push the pipe dope down inside of the pipe leaving it to potentially cause problems with taste, clogging or other issues. After you have tightened the pipe joint properly, it is a good idea to wipe the excess off of the outside with a paper towel or something. Doing this prevents more mess as you continue to work around that area.

Done properly, as described above, Pipe Dope will provide you with a sealed joint that should last for the life of the pipe fitting that you just installed.

Teflon Tape

Now, what about Teflon Tape? Why would it be less desirable than Pipe Dope?

On the surface, Teflon Tape seems to be the simplest, cleanest way to seal a set of pipe threads. This is true if it is used properly. I think, to the professionals, there has always been some question as to exactly how much needs to be used to thoroughly seal a threaded joint. It is not uncommon to find failed Teflon Tape seals when you are in the fix-it business.

These failures can result from both using too much as well as not enough of the Teflon Tape. They can also be caused by wrapping the tape the wrong direction around the pipe! Another frequently encountered problem it that the careless installer wrapped the tape so that it hung out into the open end of the pipe, thereby allowing it to come loose in the water stream and move down the line to potentially clog up a smaller orifice later on. (Think shower heads, faucet aerators, water filters, etc.)

How To Install Teflon Tape Properly

Using Teflon Tape Properly is not difficult. You just need to know a couple of simple principles to put it on correctly.

First, you need to wrap it around the end of the pipe in the correct direction! Wrapping it in the wrong direction will cause the female threaded fitting to literally peel the Teflon tape right back off of the threads as you screw it into place! This will almost always result in a leak!

So, when you look at the male threaded end of your pipe so that you are looking directly into the end of the pipe, you should be wrapping your Teflon Tape around the pipe in a clockwise direction. That will cause the female pipe fitting that it is mating with, to actually hold the tape in place as it is tightened down.

Next, how much tape do i need to use on each joint? Almost always, 3-5 wraps of tape around the pipe is enough. Ideally I like to hit a happy medium of 4 wraps every time. Too much or too little tape can both cause problems on a joint. There have been times when I have used slightly more such as when I have encountered an old fitting with slightly damaged threads and I don't have the option to get a new fitting.

Also this would be a time when you would be much better off to use pipe dope. Frankly there are even times like this when you may want to use both. First put put a coat of pipe dope on the threads and then two or three wraps of Teflon Tape around it. However, this should only be done in extreme situations as a temporary fix until you can replace the damaged parts.

One final Teflon Tape application principle, never allow your tape to stretch off of the end of the pipe (as shown above) to where it would end up inside of the pipe once it is all assembled. It is much better to not have any tape on the first thread or so rather than to have it get inside of the pipe later.

So, to keep it simple, wrap in a clockwise direction, only use 3-5 wraps, and keep it out of the end of the pipe! If you do that on a good set of pipe threads, you should never have a leak with Teflon Tape.

Final Thoughts On Using Either Type Of Pipe Thread Sealer

I very often see pipe thread sealers used in places where they are not necessary. When I do see this it is usually Teflon Tape, which points the finger directly at the DIY'er!

There are several types of plumbing connections that are designed to be self sealing and, in fact, using thread sealer in these situations is, at best, a waste, and at worst, can cause the joint to fail.

If you can look inside of your fitting and see a rubber seal, a tapered surface, or a nut and ferule, those types of fittings are designed to be self-sealing. Do not attempt to use thread sealer on them. Braided steel and the flexible supply lines for sinks and toilets, etc., generally have a rubber seal inside. Also copper and brass flare type fittings are designed to seal against themselves without thread sealer. I even came across some Teflon Tape on a crimped PEX fitting the other day. Bad Move!

So in the final opinion of this writer and many journeyman plumbers, using pipe dope is a better solution to sealing the threads on a normal pipe fitting. However, with that being said, there is nothing wrong with using teflon tape for the same purpose, as long as it is used correctly. Pipe dope is probably the easiest sealant to use correctly and is more "fool proof" for the average user.