sweating the small stuff

Idoc4u · Jan 28, 2010

In the process of sweating 3/4" copper, I noticed that on occasion I will have a fitting that I can pull apart very easily (after giving it a chance to cool). When I pull it apart, there is very little solder in the joint. However, in the process of sweating the joint, I can see the solder being sucked into the joint and the solder rolling around the joint.

Could this be occuring because if I am sweating a joint close by and the transferred heat loosens the joint and or pulls the solder out of the joint?

I am using MAPP gas, Oakey flux and lead free solder.

I appreciate words of advice.

Spaceman Spiff · Jan 28, 2010

Are you cleaning the pipe and fittings with a wire brush and sandcloth before flux and soldering?

Sponsor · 2022-01-29T12:20:58-0800

Idoc4u · Jan 28, 2010

Spaceman, I clean the fittings and pipe with a wire brush and emory cloth before applying flux and sweating.

Krow · Jan 28, 2010

I am using MAPP gas, Oakey flux

I'm guessing you mean "Oatey" soldering paste

3 reasons why it may not be soldering properly

The pipe and fitting is not clean enough, or
water in the line, or
not enough heat

Idoc4u · Jan 28, 2010

Here are a couple of ideas that may be the cause; 1. The joints that did not hold well may be joints I sprayed with water to more quickly cool the joint, 2. I applied flux to both sides of the joint, connected pipe to each side sweated and soldered one side and then the other. Perhaps oxidation began to form on the opposite side of the fitting as the heat burned away the flux.

I'm thinking that it may be smarter to let the joint cool without a quicker cooling spray of water and or let the fitting sit for 10 minutes before trying to solder the next length of pipe onto the other side of the fitting.

What do you guys think about that? Does cooling with water or trying to solder the two joints at once put the connections at a higher chance of not holding?

Thanks again.

Idoc4u · Jan 28, 2010

krow, yes I meant Oatey. Sorry for the typo. The lines currently are dry. No water has passed through the lines to date. Could you also suggest a method for testing the structural integrity of the joint. For example, if I'm not running water through the fittings until later, should I twist or pull on the joints to see if they are stable after giving them an opportunity to cool down?

Jc60618 · Jan 28, 2010

Since you say that after pulling the joint apart there is very little solder. Its probably the way you are soldering. When soldering alternate the flame between the pipe and fitting. When ready to apply sloder keep the flame on the fittng and then apply solder. Remove the flame and while the fitting is still hot put a liitle more solder in the joint. Also remember to solder a pressue fittng in one shot. Let the joint cool down for a minute or two and then wipe it with a moist rag.

Krow · Jan 28, 2010

There is absolutely no reason not to make multiple solder joints at one time. Soldering both sides of the fittings at one time , lessens the probablity of oxydization. Cooling it down with water after the soldering has been done, should not affect its integrity, unless you move the pipe while the solder is still molten.

I'm tempted to say, insufficient heat at the joint. Depending on where you apply the heat makes a difference as well. The blue tip of the flame should be placed directly to the joint/fitting being soldered.

Always check your joints to see if they are sturdy (pull, tug, shake), and you could always pump the system with compressed air to about 125PSI to make double sure. (of course, you would not need to pressurize an existing system with your test)

Cass · Jan 28, 2010

use Oatey #95 flux...there is nunbetter...

Idoc4u · Jan 28, 2010

thanks again, guys!

SteveW · Jan 28, 2010

Just to reinforce what krow says - (since I used to make this mistake myself) - make sure you are heating the fitting, not the pipe...

On a 3/4" fitting, best to move the flame to opposite sides of the fitting (180 degrees apart) to make sure it is evenly heated. Heat just long enough for solder to be drawn into the joint, which with MAPP gas will be a matter of seconds. I apply solder until it fills the joint and starts to drip off the bottom of the fitting.

Jadnashua · Jan 29, 2010

If you melt the solder with the flame touching it, you can easily melt it without the fitting being hot enough for it to wick into the joint. In fact, once hot enough, you should be able to melt the solder after your remove the flame for a few seconds at least.

JohnjH2o1 · Jan 29, 2010

On 1/2" & 3/4" pipe heat one side of the joint and apply the solder to the other. On larger pipe you have to move the flame around the joint. When you see the solder drip off the bottom the joint is full.

John

sweating the small stuff

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