When to Use Sealants on Threaded Plumbing Connections | This Old House 

So much information in under 4 minutes. This is why This Old House is the best home improvement channel.

I couldn't stop a new threaded valve into old work from a slight leak until I used the wicking technique you demonstrated. Excellent trick and I thank you for your share.

As always, your videos are awesome, very educational. Richard, you are one “VERY SMART MAN”... I know your knowledge comes from a lot of hard work, and pure determination to ensure the job you do for your customers will meet their expectations. You sir, get a “GOLD STAR” 🌟 ⭐️ 💫

You guys are true PROs! Great explanation, lots of info in a short time (thank you for VALUEING peoples' time), efficient, .... just the BEST on youtube. I surely appreciate you!

Some people just want to watch the world learn, you are those people, thank you.

So my dad, who worked with Local 3 in Denver, CO, told me to use Teflon tape and just a thin film of pipe dope after you wrap the joint. It lubricates the threads and you get a better fit up. He also recommended using pipe dope on all threads for this reason

Excellent instruction. I'm always amazed at the number of places I see homeowners have applied teflon tape. At least they were aware of the idea.

Learned the difference between NPT and NPS the hard way. Should have watched this video before I started the project, it would have saved me a lot of grief

“Oh yeah, I never noticed that before.” So funny.

as a plumber, I always use both teflon tape and pipe dope on water connections. Drainage you can get away with just dope, but I don't chance it with water.

OCT. 2020. Thank you, was installing/replacing a hand held shower head. Thought I might need Teflon tape, but was not sure how to use it, this old house, needed almost ten wrap around before I stopped it from leaking at the shower pipe.

In the UK taper threads for domestic fittings have virtually died out. Pretty much only seen where the radiator unions are fitted. There are a few instances where the are joints with parallel threads. the only way to seal these is too stuff them with tape or the latest silicone impregnated cord, but it's hit and miss and frustrates the life out of me. Taper fittings work 99% of the time and give a degree of positioning, so are a great solution to most joints, so I'd love to see a lot more available on the UK market for domestic installations,

One very important point you failed to make - when wrapping the Teflon tape onto the pipe - you must wrap it in a clockwise direction. Second point regarding the tape - do not wrap the tape beyond the end of the pipe.

I use "pipe dope" on all my plumbing threads, so that I can disassemble the unit in the future. I use it on the screws that hold the stop washer, threads on the union, when I service a valve body... just a little dope on the threads goes a long way to make a future repair sooo much easier!

Pipe dope also acts as a lubricant to allow a smoother tightening with less friction. As well as filling the threads to form a more liquid seal.

Sooo much hardcore information in such a short video. Thank you so much good job!!

Never heard of the wicking before! Thanks for the video.

Wicking is an old technique. I recently replaced my father's boiler, put in in the early 60s but the piping was from 1904, and the piping is all wicked and uses a black type of sealant that sets up hard. Without heat, I actually used a 48" pipe wrench with a 5 ft cheater to get 2" to loosen. Tape, plus dope. That's what were taught in apprenticeship school. Never fails.

You have to be careful using any kind of Teflon (tape or paste) on PVC since it's slippery and is easy to overtighten the joint. Lasco actually recommends not using it, but using a PVC-appropriate sealant.

I believe "Blondie" is asking questions that ppl like me, who have never done this before, might want to know. His questions may seem unnecessary to some but they helped simplify matters for me.

Great vid! Just what I was wondering. As with many things, "Different Strokes for Different Folks!"

I always use tape and dope (Blue monster and T Plus 2) when it is critical that there are no leaks. Irrigation and non pressure systems I just use tape.

I just installed a whole-house water filter and the mfg instructions explicitly stating not using dope or sealant because it could harm the plastic filter housing. Just putting that out there that it's not always a go-to solution.

Some thread sealants are incompatible with plastic pipe especially CPVC or ABS. Can soften the plastic leading to failure. The yellow sealer especially.

Very cool, a plumber I know swears by Rectorseal Tru-Blu pipe slealant. Great info, thank you. 👍👍👍

This was exactly what I needed with great explanations and visual examples.

Thank you for your excellent work!

the one part they missed is that the soft set liquid sealant helps keep the threads so they will move later for rework. so if you have a wc bolts if you use the liquid on the threads as new it will help on holding back corrosion so you can remove or tighten the bolts at a later date. same on the threads for the new style faucet. a dab on the threads help keep it from welding the two metals together chemically. and yes on the yellow soft set harvey's liquid pipe sealer on LP and NG connections for black pipe as well as black to brass connections.

going to finally start piece working gas and ive done it a bunch of time but by the hour and ive got it kind of down but this is refreshing to see cause i will be on my own now

Teflon backed up with dope makes a good sealed high for a long time.

Make sure you wrap your Teflon tape in a clockwise direction!!!!!

I usually use both tephlon tape and pipe dope on my black iron threads, never use pipe dope on PVC threads pipe dope can actually erode pvc pipe over time

Im an electrician not plumber. But with plumbing fittings ive noticed that it seems anytime you connect brass fittings you most likely won't need sealant or teflon. My guess is because brass is a soft metal and smashes together to make a water tight connection. He pretty much showed that with the radiator, but he didn't mention about the brass. But that seems to be the case when you see brass

Most PVC manufacturers actually recommend non-hardening thread sealant over teflon tape for threaded PVC connections because it seals better and has less chance of damaging the fittings. IME, it works significantly better than teflon tape.

The threads on the National pipe thread (the one that you show on your black iron pipe) are actually what creates your water tight seal, pipe dope or teflon tape help you screw the fittings on a little easier because they provide some amount of lubrication but don't really play much of a role in sealing on black iron pipe with a NPT, if you made a proper thread and the pipe is snugged in it, in theory it shouldn't leak. Also always cut test threads before you start using perfectly good lengths of pipe because otherwise you could waste a lot of pipe before you know there is a problem.

They didn't mention it but iam a plumber and any time I do a water line connection not a faucet supply or flared fitting. I will wrap pipe with teflon first then pipe dope over. This hasn't let me down yet. If you don't want problems use both.

ALWAYS Always always read the msds sheets and manufacturers guide before proceeding to help!

Because of the way this video is presenting the information, If I put on my "never done this before" hat, the message is clear: Use teflon for plastic pipes an the dope for metal pipes. Which is, of course, wrong. If you start with metal, continue with metal. If something else needs to be used for plastic, that can be both done and explained WHY it is true.

In the uk you can get various brands of non setting paste but one in particular called Rocol almost has a consistency of chewing gum and never fails when you paste a gas joint.

I had to replace an ancient frozen toilet stop valve. It was threaded onto a 1/2 galvanized pipe but the pipe had straight threads and the valve had a washer (which was mostly gone). I could only find tapered thread fittings and didn't realize the pipe had straight threads, and since there is a quarantine on, I could only find Home Depot open. The FIP valve screwed on maybe 1 1/2 turns before stopping (since the straight thread doesn't really mate up). But in desperation I just slapped on pipe done and cranked down hard on the valve. It's not a great solution but I finally got it to stop dripping. I cannot find straight threaded stop valves anywhere! (Maybe cutting and rethreading the pipe is the solution?) Or somehow connecting an adapter...

Perfect! Love Richard.

Great video, but I wish you hadn't hid the labels on the type of pipe dope you use I would like to get the same kind you use because I trust you guys to get the best but I don't know what brand you used

2024 : still top quality

Just spent 3 hours installing a faucet in my bathroom. The 7/8 water feed side would not for the life of me thread onto the facet inputs. The small side threaded on by hand no problem. felt like it was going on straight, would seem to be tightening then it looked like it was slipping off steel braided water line

As another pointed out, I saw another video by someone else that claims that tape/dope doesn't really seal anything but allows the threaded items to go together more easily. I hired a plumber once to change an outdoor faucet and he actually used both the tape and dope together. I visit many RV parks and attach my water hose to their spigots. I notice many use teflon tape and it still drips. I carry a bunch of extra rubber water hose gasket inserts to cure that problem. I don't use teflon tape or dope at all at the RV parks. This week, I eliminated my garbage disposal as I never really use it. I always screen food debris then toss it into the trash and never send it down the drain. Because my drain pipe under the counter comes out of the wall at a weird angle, I had to do some custom connections without having to open up the wall to redo the drain pipe. In turn, some of the connections were off a hair so water was dripping out of the threaded connections. No amount of teflon tape or dope helped. I ended up using silicone on the outside of the connections which stopped those pesky leaks. I'll do a more permanent repair in my next life.

I had hoped to see how best to seal the joints on sink connections around the p- and j-trap fittings, where there is a nut with what appears to be a gasket of nylon or teflon. Should pipe dope or teflon tape be applied there?

Get Permabond. It's a pipe thread sealant that can be used on water, gas, or other petroleum product pipe up to 2" It's the best I have ever used.

Sealer not always needed on pipe thread. For instance. If it’s NPTF. F for fuel. The sealant telfolon is intended for lube in the assembly process. The seal is caused at apex of the thread. Interference deformation.

Whats best for 1 inch male PVC to 1" galvanized female pipe? Thread sealant, Teflon/PTFE Tape or pipe dope?

The threads do seal on their own. Teflon tape isn’t a sealant, it simply provides lubrication so you can turn the pipe more to make the threads lock together better

I enjoyed the show, very clever piece of content!!

THAT is a very helpful video! Much appreciated. Thanks guys.

Everyone needs a Rich neighbor.

Seeing as a lot of people watch This Old House programs and videos, it would be great if you would actually follow information. In this video Richard Trethewey leaves two pipe dope containers open and gets some of the material on his fingers. My pipe dope container (and very likely the one he is using) says "harmful if inhaled". Even working outside you can smell this stuff. So you're inhaling it. There are also skin contact warnings. Unless Richard has enough knowledge of toxicology to decide that these warnings are exaggerated, it would be a good idea to respect them. Especially when providing instruction in a public forum.

My man Richard!

You put white teflon tape on PVC threads but they say not to do that I thought on the white plastic pipe?

Excellent presentation TOH. I too have wondered when to use dope or Teflon tape or nothing. Now I have a better understanding.

To the point and Very useful video, Thanks

If I really need it sealed I do Teflon tape first then pipe dope. But always the Teflon first.

Great video. One question is how tight to make each type of connection... I know most flex lines tell you how far beyond finger tight... If a fitting leaks, is the dope compromised?

I like putting anti seize on steam and condensate unions

I've installed hundreds of boilers. I always tape then dope. Especially when I'm going from old black iron to copper. It's cheaper and less time consuming that filling an entire system, only to find a leak, then have to drain back down and disassemble and redo.

Great stuff , thanks guys 👍🏾

My uncle who is a plummer for years only uses wicking with this paint it will never leak and it will unscrew after 100 years he says that teflon is for amateurs in big jobs with huge pipes you can not use teflon

I always wondered what to use on that one spherical joint on the P trap. There is no rubber seal there. I usually just use some plastic safe silicone grease.

These videos are fantastic!

While the sink was there it would have been a good time to show how to properly dope up the threads on a sink drain. So many people do it wrong.

Unions are used in order to make it easy to remove and reinstall something. To use 'dope', or any other sealant is a mistake that only lay people will do. Sealants are adhesives and while they don't dry brittle, they do dry hard. Often that hard that heat is needed to dismantle. If that union joint is dismantled in the future, what you are left with is a very filthy joint that requires a lot of work to get clean again. If the two faces have not been faced properly and there is a leak, only then would you use Teflon tape on the male face but NOT that white rubbish, it is too thin. Either use pink or yellow, (yellow is for gas but not exclusively so). Then when tightened, the joint will be sound and very easily cleaned up after dismantling. Another tip; When applying Teflon tape to a thread, if it is plastic it is better to rough the mail thread up by dragging a hacksaw blade over it at 90 degrees in several places around the thread. If it is brass, use a set of tongue and groove pliers, we call them 'multigrips' and work you way around the thread, crimping little notches in the thread. This will give the tape something to 'grip' and not slip as you screw the fitting together. NOTHING is needed on the thread of a union, as mentioned. The only time I use a combination of thread adhesive and Teflon tape is where the brass thread is very loose and often chromed as well. When the threads a deeply cut and very loose. it is always good to leave them for sometime after screwing home to give the adhesive time to 'go off'. Ken From Lyneham Plumbing Services.

Great tips guys!!!!!!!

I use PTFE take to seal threads where needed like described, but I also use it as a thread protection, like anti-seize because most metal plumbing oxidizes over time and can seize threads making it very difficult to break a connection. Is this okay?

Here in singapore.. we usually use the Teflon tape on the water hose even if there's a rubber gasket..😁

You forgot to mention the direction of wrapping the tape.

Thanks. Now I know.

Nice info in vid. How to deal with a cracked threaded pipe-end in a wall, which is causing seepage.

I have a 1 inch cold water supply line attaching to the well casing Male pvc to female metal I didnt tighten it quite enough and I have a small pinhole air leak where the threads meet the metal. I cant tighten it because everything else is glued. What can I do without taking everything apart?

ALL I WANTXTO KNOWXIS CAN TEFLON TAPE BE USED OF LP GAS FEED LINE GOING INTO BACK OF STOVE!

Fantastic content as always

Please explain wicking string again. What type string? Only cotton? What about valve stems on outdoor faucets? JoeB

Good informative video! 😎👍

Richard, where do you use plumber's putty? Everything!!!

He's no Bob Villa but great information

Good instructions

very helpful!

Just did some research and the pvc manufacturers say not to use Teflon tape on their threaded fittings. Only proper thread sealant that stays soft. Don’t use anything else. Don’t use pipe dope that get hard either. This advice is only for plastic fittings, metal ones are alright to use tape and hard setting dope.

Good advice for low pressure handyman stuff. High pressure mains I would use different stuff this stuf needs to be buried before you can even test you do not want failures if in doubt use both. America still using NPT type threads?Cheers from Oz

__________________Teflon and or pipe dope is for non-stick. I use pipe dope with teflon in it, and both dope and tape on brass to dissimilar metal. All of this is to keep metal from chaffing inside the joint and balling up. It lets the 2 surfaces slide together so that the METAL ON METAL makes the seal. (Plumbing 101) Teflon and or pipe dope is not supposed to make the seal. It's so you can take it apart someday as well. I use it on every thread (except maybe supply connectors) so that years later the plumber can get it apart. If you are using this to make the seal you are cutting substandard threads.

Thanks!

My situation or leak it's just like he showed with the compression fitting and that tapered compression going into that nut. I seen that he used pipe dope to help seal it. I'm just concerned that the dope might get diluted from the steam and maybe we'll keep leaking. I tried tightening it but that is it helping no matter how tight I make it

Do you ever use teflon tape and pipe dope together? I see some videos where that is done.

This is a great video

if the ground joint is damaged in any way you replace not dope

Thank you.

Ouch! Never use compound or tape on a ground joint, as it relies on a true metal to metal seal for efficacy. Sealants are subject to creep and compromise the joint in the long term. Indeed, be careful to remove any oils that may have been applied to prevent rust during storage or left over from the machining process. One should also be careful not to contaminate wetted surfaces by sloppy application as was done here.

Well done. ..👍👍👍👍👍

For thermal installation-radiator pipe with Hemp or teflon tape?

Badass!

I always wonder about brass to brass. And should guys be using tape or dope on flared fittings. I think not but see it all the time.

Is liquid pipe dope or stick pipe dope best for a water heater gas intake?

wow, No mention about the difference between gas and water sealent.

what about a coupler?