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 High Temperature Pipe Dope
Author: george 7941

Is there a thread sealant available that can reliably withstand the heat of soldering?

Somtimes it is more convenient to make up a threaded joint first and then solder copper pipe on to the copper/brass fitting.

An example would be a threaded 90^ elbow where if the pipe is soldered on first then there is sometimes not enough room to swing the pipe when threading the elbow on. What I have been doing is soldering on a short length so that the threaded joint can be made and then extending the short copper pipe with a coupler.

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 Re: High Temperature Pipe Dope
Author: e-plumber (NY)

What I normally do is solder the adapter onto the pipe, let it cool then thread it into the 90, as in your example; you can make up the 90 first, in most cases.

There is always the situation were you can't though. I've used Megaloc and RectorSeal #5 with success, but the key is NOT to heat the solder joint too much...

e-plumber
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"The society which scorns excellence in Plumbing as a humble activity and tolerates shoddiness in philosophy because it is an
exalted activity will have neither good Plumbing nor good philosophy: neither its pipes nor its theories will hold water." -
John William Gardner 10/8/1912 - 2/16/2002

Repair your leaking Plumbing fixtures ASAP [www.theplumber.com]
This slow drip will waste 7+ gallons of water per day.

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 Re: High Temperature Pipe Dope
Author: LemonPlumber (FL)

what is 100% Teflon.virgin paste is what i use .have you ever heard of heat sync.wrap a wet cloth around the cold side to your fittings before you solder if the rag starts on fire your getting it to hot.if it takes you a little longer to do it the way you know you can make a good lifelong joint stay with it .sounds like you have a limited room issue and thats a little different from being able to assemble the valve on the ground and hang it into the manifold later.some times it can be a different torch tip.lower temp. solder.Loc-Tite will burn but if it gets time to cool completely its like epoxy.just hate to ever go back on it.



Edited 2 times.

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 Re: High Temperature Pipe Dope
Author: hj (AZ)

The dope is not the problem. The problem is the expansion of the male thread when it is heated, compared to the temperature of the valve body. The adapter being much hotter will expand in the female thread and enlarge it, but when it cools the female thread may not shrink to its original size because it was stressed by the adapters expansion, not by its heat. This can/will cause a leak.

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 Re: High Temperature Pipe Dope
Author: LemonPlumber (FL)

hj unless you get the fitting hot enough to temper them.they will return to there natural size when they cool.

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 Re: High Temperature Pipe Dope
Author: george 7941

hj. Good point that you bring up, never thought about it before.

Your point will not apply to female threaded adaptors which are being heated up. If the dope could stand the heat the it should be possible to make up the pipe joint and then solder.

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 Re: High Temperature Pipe Dope
Author: PlumerDan (CA)

i have made up many a shower valve set up using teflon tapr. soldered as usual and had no leaks. i always thought teflon was made for that popose? just don't over heat it i guess.

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 Re: High Temperature Pipe Dope
Author: redwood (CT)

Teflon is good to about 500 degrees F.

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 Re: High Temperature Pipe Dope
Author: george 7941

The maximum temperature for teflon tape and a lot of pipe dopes is so close to temperatures needed for soldering that I have always soldered first and then made the pipe joint.

Shower valve bodies, because of their thermal mass, need to be heated about four times as long as a normal copper fitting to reach solder flow temperature. I have never dared to heat up a taped shower valve joint. However, after Plumerdan's post, maybe it is time for me to try it.

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 Re: High Temperature Pipe Dope
Author: george 7941

Just thought of something. Plumerdan's results are the opposite of expected results from hj's post since shower valves usually have FIP threads and MIP adaptors get screwed in.

Perhaps the extra wall thickness at the FIP threads of a shower valve, as compared to a usual FIP fitting, gives the brass enough 'springiness' that the female threads contract back to their original dimensions.

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 Re: High Temperature Pipe Dope
Author: e-plumber (NY)

We've all soldered adapters into/onto shower valves, fittings, valves, nipples, pipes, etc., without
worrying so much about it. Too much, or not enough heat will always cause a problem.

e-plumber
-----------------------------------------------------------------------------------------------------------------------------------

"The society which scorns excellence in Plumbing as a humble activity and tolerates shoddiness in philosophy because it is an
exalted activity will have neither good Plumbing nor good philosophy: neither its pipes nor its theories will hold water." -
John William Gardner 10/8/1912 - 2/16/2002

Repair your leaking Plumbing fixtures ASAP [www.theplumber.com]
This slow drip will waste 7+ gallons of water per day.

Post Reply

 Re: High Temperature Pipe Dope
Author: hj (AZ)

The fitting will but during the process it will stretch the valve because the two are not expanding at the same rate, unless you heat the valve with the flame also. That stretching will not shrink back when the fitting does.

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 Re: High Temperature Pipe Dope
Author: hj (AZ)

It does and I have done it occassionally when the job demands it. But as a practical matter, any shower valve with male threads is normally a dual use connection with sweat capabilities on the inside of the port.

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 Re: High Temperature Pipe Dope
Author: hj (AZ)

you could also go the easy route, which I usually prefer, and that is to solder the male adapter into the valve body. Then there is no possibility for leaking, just get the valve oriented properly first.

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