Secret to Sweating Brass to Copper?

bsmhsJanuary 28, 2008

Hello All,

I spent the last 3 hours replacing the water heater at my house. In doing so, I had to replace the in-line 3/4" valve. I put a ball valve in this time which is brass and can't seem to get a completely water tight fit sweating it to copper pipe. I have no problem with copper to copper. Is there a secret to sweating a brass valve to copper pipe? Thanks for any ideas!

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What kind of torch are you using? Maybe you're using an old torch that isn't quite hot enough, and you're burning off the flux prematurely.

On the other hand, maybe you're not applying enough extra solder after you've removed the flame. Theoretically, it's supposed to get sucked into the joint and that's it. But I see plenty of plumbers add extra solder to the joint afterward, while using a flame very sparingly to get it to flow.

I'm sure the pros will chime in soon enough, but those are my ideas.

    Bookmark   January 28, 2008 at 10:30PM
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I just did exactly what you did, but no leaks (so far....).

I sweated 3/4 copper to 3 full port ball valves, brass bodies. I used a full propane torch, max flame length, spread lots of flux onto both valve and pipe after a very thorough scrub with steel wool, and was surprised how long it took to warm up enough to melt solder.

I made sure to keep the flame on until I heard the sizzling of melting flux finish, and kept the flame going until I saw smoke leave the open valve. I then touched the solder to the joint opposite the flame, and held the flame on the joint while pushing the solder. I then removed the flame and made sure solder was around the whole joint. I didn't hold the solder INTO the flame, just held the flame to the valve while touching the joint with solder. I made sure to keep the flame at the end of the valve body, not the pipe. The pipe will heat and cool quickly. The valve had much greater thermal mass, and heats(and cools, ouch!) much more slowly. If the valve stays hot, the pipe inside it will too.

Hope this helps.

    Bookmark   January 28, 2008 at 10:45PM
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IÂm not a plumber so I need to use methods that are easier for me but probably a waste of time for a pro. For what itÂs worthÂ

I never solder a valve to avoid overheating the gasket and packing material, I think even a brass ball valve has some damageable components. I use female threaded valves only.

I would cut out an 18" length of copper tubing from your heater, and solder a copper male threaded fitting to one end.

To the tubing still attached to the heater, I would solder on another threaded male fitting, and using dope or tape screw on the valve.

Trim the removed section to the proper length and screw it into the valve, add a copper coupling to the other end, and reconnect it. Wrap the valve with a wet towel and solder the coupling on.

    Bookmark   January 28, 2008 at 11:16PM
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You shouldn't have a problem soldering copper to a valve if you have enough heat. I'll bet you that's where your problem lies. The Bernzomatic TS4000 turbo torch head with mapp gas would probably solve your problem.

    Bookmark   January 29, 2008 at 10:35AM
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Thanks for all your input. I ended up taking it apart and starting over. First I used emery cloth and sanded both surfaces real clean. Then I preheated both the valve body and the pipe, then brushed flux on both sides and slipped the two together. Continued heating on the valve body until the solder melted into the joint from the opposite side from the flame. No leaks and now I can take a hot shower.

Thanks again. All your suggestions were definitely helpful!

    Bookmark   January 29, 2008 at 4:31PM
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Be sure that you are applying heat to your fitting rather than your pipe. Place the flame close to but a little away from the end of your ball valve. You have to get both surfaces hot and the brass heats up so much slower. Once that brass gets heated it, the copper will be more than ready to take solder.

    Bookmark   January 31, 2008 at 7:09AM
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I have to disagree with [jmricker]. Heat the pipe first, near the valve. The pipe will expand with heat and make better contact with the valve's socket. Then heat the valve and apply solder. Any solder drops or drips or fillet are wasted material. All that is required is that silver ring around the joint. Always open globe valves when heating them, this will move the disc off the seat to prevent damage.

    Bookmark   February 1, 2008 at 8:27PM
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My plumber heats up the valve on one side until the solder melts on the other side, that is when it is hot enough. One touch with the solder at that temp and it just flows around the joint effortlessly.

    Bookmark   February 6, 2008 at 12:24AM
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