Teflon Tape Melt?


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Old 12-30-07, 10:27 AM
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Teflon Tape Melt?

I need to solder a new 3/4" threaded copper adapter to existing copper pipes. The problem is I need to screw it onto a tankless water heater before I solder it to the pipes. Will heating the adapter to solder it cause the teflon tape to melt and result in a leak? Can I use something else on the threads that won't melt?
 
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Old 12-30-07, 10:38 AM
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Teflon tape or any pipe sealant does not really act as a gasket.
It is used to lubricate the threads to allow the mating threads to more smoothly mesh together.
If you have the fittings properly torqued you should not have a problem.
Also, if you use a heat sink like a wet rag near the base of the fitting it will minimize heat build up.

Unless you are coming right off the fitting with a street elbow you will usually have a piece of straight pipe that you can pre- solder to the fitting prior to threading it into the tank.

Also, it wouldn't hurt to have a regular or dielectric union to allow the tank to be disconnected.
 
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Old 12-30-07, 11:02 AM
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If this has to be a static installation, you may want to consider installing a union above it so you can solder your fitting and then screw it into the application, joining it together with the union. Makes it easier to service later, also.
 
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Old 12-30-07, 11:52 AM
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So it sounds like even if it melts it shouldn't affect the seal. I was originally going to use unions until I saw how expensive they were (~$18 at Home Depot). I see dielectrics are much cheaper based on what I could find online. Maybe I'll use them instead. From what I just read about them I think I would be defeating the purpose since the tankless water heater appears to have brass threads and the dielectric is steel so it would still result in disparate metals in contact.
 

Last edited by DlMyself; 12-30-07 at 12:13 PM.
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Old 12-30-07, 11:52 AM
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Teflon dope can be the answer also.

If it heats and melts you aren't really losing material in/on the threads, as you MAY have happen with the tape. Tape CAN be built up. The proof of this can be had if ever you install a tub spout or shower head: You are aiming for tightness to occur just as it points down. With one wrap of tape it gets tight pointing straight up. So you remove it and put on a couple more wraps of tape and now it gets tight pointing down, the way you intended. With the dope, there will never be a build up. The excess will always ooze out. If you heated the fitting this ooze will congeal and solidify more around the joint.

As suggested, it is best to try to pre-make up the fitting and some pipe first. But there are instances where you can't very well. And it sounds like you stated that in your OP.
 
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Old 12-30-07, 01:18 PM
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Teflon tape is in fact a thread sealant. That's what it is used for and that's how it is marketed by both manufaturers and by Dupont. While it certainly acts as a thread lubricant, that is not it's primary purpose.

There are a couple of DIY sites that make the same comment about it not being a thread sealant. They are mistaken. IMO it5's become an urban legend sort of thing.

I have used teflon tape in gauge piping joints up to 3000# air and liquids up to 600#. Trust me, I could torque those joints to near failure and they would still leak w/o teflon tape.

Most teflon tape is spec'd to 500*F. Keep the joint below that temp and you won't have a problem.
 
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Old 12-30-07, 01:25 PM
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At what temperature does solder melt?
 
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Old 12-30-07, 02:39 PM
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I think 750 off the copper .I use tape first and then paste learned from a old timer
 
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Old 12-30-07, 04:25 PM
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I think the lead free solder has a higher melting point than the old 50/50. I usually just wrap a wet rag around anything that I don't want to get too hot.
 
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Old 12-30-07, 04:58 PM
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Buy the unions. They are a tiny amount compared to what you have already spent with this job and they are the correct way to do the job.
 
 

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