Thread seal tape for plumbing. What’s the best?

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Alaskajohn

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I am running low on plumbers thread seal tape and went on Amazon noticing a bunch of different types. I’ve never given it much thought before.

Is there a clearly super thread seal tape? I might as well stock up with the good stuff if there is truly a superior product. This is the type of stuff unsung hero item that could save the day.
 
I really dislike thread tape. It can come undone and fill passages. It can leak if you don't put it on correctly. It can make it easy to split fittings by reducing the friction in tightening.
I much prefer the paste and gel sealers. There is one made specifically for propane and others for oils water and alcohols.
 
I really dislike thread tape. It can come undone and fill passages. It can leak if you don't put it on correctly. It can make it easy to split fittings by reducing the friction in tightening.
I much prefer the paste and gel sealers. There is one made specifically for propane and others for oils water and alcohols.

Any specific products that you can suggest? This is the type of advice I’m looking for, as I have a love/hate relationship with the tape.
 
The best "all-purpose" sealer is Loc-tite 518 anaerobic flange sealer. It seals against everything and it can be used on flanges, gaskets, and threads of all pitches.
 
If you are using it for oil, stay away from anything with teflon in it. Teflon tape or paste can get into your boiler fuel pump and nozzle. Pump warranties are void if you use teflon. I pick a heavy tape so I can use fewer wraps and buy longer rolls for a better price.

Edit: If forced to use teflon I leave the first thread bare.
 
The best "all-purpose" sealer is Loc-tite 518 anaerobic flange sealer. It seals against everything and it can be used on flanges, gaskets, and threads of all pitches.
Exactly! Ask anyone that has worked with hydraulics for years (like me).
Teflon tape is never used because no matter how tight you screw fittings together, they are still loose and will move.
We used 2 types of the loc-tite gel. I can't remember the numbers, but you used "cherry-jelly" for small stuff and "grape-jelly" for large stuff (larger than 1.5").
The only thing we used Teflon tape on were pneumatic fittings for the ease of disassembly and fittings coming loose and leaking were no problem.
 
The best "all-purpose" sealer is Loc-tite 518 anaerobic flange sealer. It seals against everything and it can be used on flanges, gaskets, and threads of all pitches.

Can that be used on PVC fittings?
 
I use monster brand teflon tape. Its a blue tape. When i use teflon tape i also use pipe dope with the tape. I put the tape on first and then the dope. For dope i use jomar but am not really picky as long as it is a teflon based dope.

When i was an apprentice the rule was to only use pipe dope on pvc threads. That is no longer the standard. Now many times i use tape on cleanout caps. Its the only way to pass a air test for inspection.
 
I use monster brand teflon tape. Its a blue tape. When i use teflon tape i also use pipe dope with the tape. I put the tape on first and then the dope. For dope i use jomar but am not really picky as long as it is a teflon based dope.

When i was an apprentice the rule was to only use pipe dope on pvc threads. That is no longer the standard. Now many times i use tape on cleanout caps. Its the only way to pass a air test for inspection.
Can you tell me about the air tests please ?

Being an amateur I used PVC for waste lines only and never learned about air testing.

Curious

Ben
 
Way different beast. For metal pipe, I use Rectorseal #5. For PVC, I use Oatley purple primer and the blue hot seal.

You would put those on plastic/pvc threads?
 
Jeez I'm a dummy. I always just got whatever thread tape they had at the hardware store, wrapped it a couple times, and cranked 'er down tight. It usually worked! Although the last hydraulic line I did at work, which was a steel fitting into an aluminum block check valve, didn't go so well. I put just a little too much ass into that one when I tightened it. When I energized the system there was hydraulic oil up in the trees... 🤦‍♂️
 
Tape comes for different purposes. Such as for gas lines. There are multi purpose thread tapes around. You get what you pay for. Since a roll lasts a long time I buy the best I can.
Pipe dope is a different animal. I prefer the dope myself. Again get the good stuff. I've had it freeze n used it after stirring but recommend keeping it from freezing.
I would never use thread tape with dope.
Also pipe threads taper in. If using tape on pvc fitting I do not wrap more than 3 wraps as it can split the fitting if overtightened.
For me n hydrolics I do not use tape. Generally they are specific machine cut to match without either. Where it threads in a steel block such as engine or hydrologic cylinder I use pipe dope.
I do keep both around
 
I use dope with tape all the time. Very common practice. A few years back l piped a marina. We used 30 thousand pounds of iron pipe. I taped and doped all joints. According to spec we had to perform a hydrostatic test to 150 pounds. Passed with flying colors, not had to redo any joint. To me the proof is in the pudding.
 
When working with hydraulics between 2800PSI to 5000PSI tape is a big no go! JIC fittings or ORFS is the norm. If I have a problem fitting I coat the o-ring with 518 loc-tite and it never fails. It is the only sealant that will seal with an o-ring. Dipstick tubes for automatic transmissions is a guaranteed seep spot but they remain dry if coated with a bit of 518. Oil pans, timing covers and thermostat housings all stay sealed with 518. They all come off and clean easily for re-installation. Screws and bolts that go into oil reservoirs are easily sealed with 518 and bolts through banjo housings seal perfectly and stay sealed even with brake fluid, steam, and oil.

The nice thing about 518 is that it expands as it cures to fil gaps up to .25 mm.
I have never tried it with PVC or ABS pipe and since the sealants they use actually melt the pieces together I would use the correct sealants. for sealing threads on those fittings I would likely use tape unless something else was recommended.
 
Before I retired, we stopped using Teflon seal tape & used the Teflon brush/paint on, as it last much longer.
Some even use only flex pipe Dope, not any Teflon product. I do not use Teflon on metal threads or PVC, I use pipe dope. I use plumber's putty were needed.
 
Before I retired, we stopped using Teflon seal tape & used the Teflon brush/paint on, as it last much longer.
Some even use only flex pipe Dope, not any Teflon product. I do not use Teflon on metal threads or PVC, I use pipe dope. I use plumber's putty were needed.

The problem I needed to fix was where the PVC pipe screwed into the sink drain. So I used the last of my plumbers tape on this thread. I will need to replace the PVC pipe as it appears to be a bit stripped but so far so good. It may be months before I can get into town to find the right pipes for what I need. The store was sold out when I was there in Sept.

So you are suggesting that I put pipe dope where the PVC pipe screws into the metal sink drain if it leaks again?
 
The problem I needed to fix was where the PVC pipe screwed into the sink drain. So I used the last of my plumbers tape on this thread. I will need to replace the PVC pipe as it appears to be a bit stripped but so far so good. It may be months before I can get into town to find the right pipes for what I need. The store was sold out when I was there in Sept.

So you are suggesting that I put pipe dope where the PVC pipe screws into the metal sink drain if it leaks again?
No. First if it is Not leaking do not touch it until you have the right part. The only way to fix stripped threads is cut new threads or replace the defective part when you go to town. You would use pipe dope on threads & plumbers putty on sinks as a gasket.
Plumbers putty is not for threads.
 
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In the last day I have intalled four sinks, three lavs and a laundry tub. I have to wonder how many I have installed in the last 35 years. I have used pipe dope, teflon tape, teflon tape and pipe dope. I cannot recall evet having a problem with any method.

I like a teflon based pipe dope.

I have found that on a metal threaded tail piece teflon tape is required because it is not a tapered thread.

This is all based on plumbing and hydronic piping and boiler work, wet and steam.
 
We used 2 types of the loc-tite gel. I can't remember the numbers, but you used "cherry-jelly" for small stuff and "grape-jelly" for large stuff (larger than 1.5").

Loctite 569 for smaller threads, Loctite 545 for larger threads metal to metal. For pvc I prefer Great White ptfe pipe dope. Pipe dope is also used on threaded black iron pipe for steam boilers.
 
Loctite 569 for smaller threads, Loctite 545 for larger threads metal to metal. For pvc I prefer Great White ptfe pipe dope. Pipe dope is also used on threaded black iron pipe for steam boilers.
The great thing about the anaerobic sealants is any excess that is inside and not captive between the threads, it does not harden and can be flushed out with the fluid.
If you have ever fished a tiny thread of teflon tape out of a stuck relief valve that had a whole piece of equipment down, you don't use teflon tape anymore :mad:.
...Now back to PVC pipes.:p
 
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