I’ve done a considerable amount of plumbing but something occurred to me today and I’m interested in opinions. I’m doing a project that requires an unusual number (for me) of threaded connections that are in turn sweated to pipe. I use pipe dope on my threaded connections and I’m curious as to whether getting the dope that hot will “boil” out the dope? Never had a problem but it sorta made me wonder whether I should change the normal order I’d work in order to sweat the connectors first in order to not overheat the dope… anyhow, curious what ya’all think?
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It won't affect the dope, that is the order you should do it.
DDay...
Want to make sure I'm understanding you. You make the threaded fittings up and them sweat the pipe? Vt's suggestions notwithstanding, it would be a lot easier in this case to dry fit everything and then sweat the pipe as long as I'm sure it won't affect the pipe dope. Like I say I've never had a problem but there are a lot more threaded connections than I'm used to making in one shot and I'm being overly cautious.
Thanks as always for the advice...
I always sweat the adapter before threading it in.
Here's how I do it:
Sweat the fitting/pipe.
Cool it in water and wrap with three turns of Teflon tape in the direction of the threads.
Smear a little pipe dope over the tape. (I prefer Gasoila brand)
I then warm the female fitting a little trying to judge the max working temperature.
While it's still warm, I screw in the male adapter.
Be careful NOT to over tighten.
It may seem a bit extreme, but it's the way I've done it for years and I go back later and there is no seepage. I use the same method if I'm threading together a boiler header with iron pipe.
mike
Thanks Mike,
Interesting idea to use tape and dope. I'm hoping it'll be ok to sweat the adapters in place in this case since there are a number of elbows etc that are gonna be hard to keep aligned unless I can assemble the whole mess first and then sweat it all together. But I appreciate taking the time to respond...
PaulB
I think you can go either order, depending on the circumstances. Sometimes it works out better to sweat the first piece of pipe in place, then thread the connectors together, then sweat the rest. In other cases it's easier to get everything aligned just right by threading first, then sweating everything. (What you don't want to do is sweat everything together first and then realize that you can't twist anything to thread stuff together.) When dealing with plastic parts (eg, the plastic body of a water filter), you should always sweat first, then thread. And it's not a dumb idea with some valve bodies, if they are the threaded fitting type.
If you have the room......wrap a very wet towel around the pipe in front of the doped joint you'd like to protect from overheating.Knowledge is power, but only if applied in a timely fashion.
I always try to sweat the adapter before threading it in, but, if you have to do it the other way around this method will certainly help. Careful not to over tighten and crack the cast valve. It's easy to do. Be sure to direct the heat away from the valve body and as mention before, 'keep it cool'.
Another tip; Ever wonder how to prevent that ugly silver streak when sweating a fitting on a vertical pipe. First warm the fitting letting the flux run down the pipe. Wipe the excess flux off. Now continue to heat and add solder and wipe your joint. Solder won't go where there is no flux.
With the use of PEX, sweating joints will someday become a lost art like leading a joint is now.
mike
Great tip about the flux Mike... I never thought about that but makes perfect sense!
PaulB
Thanks for that tip VtMike.
If you can screw on your fittings after sweating, fine if you have to screw them in before sweating I would not sweat against the dope. What we do in trade is to sweat a short piece of tubing on the adapter, and use a coupling. Pipe joint compound has a temp. rating, it is usually less than the melting point of solder. Check the information on the can. You may get away with sweating against the dope, but the one time that it dosen't work it will bite you in the axx. LOL.
Well, sweated everything together this morning and no leaks. But I got some great tips for the responses and I'm very grateful. Thanks everyone!
PaulB
Edited 5/28/2005 11:17 am ET by PaulB