I am wondering if I have a problem. I sweated a copper/brass gate valve to 1/2" copper pipe. I then turned on the water to check the seal. The connect seems to be good. The question is I want to sweat another piece of 1/2" copper pipe to the other side of the value without turning off the water and or draining the pipe of the water. I fear the differential in temperature from the cold side to side being sweated will cause the casing of valve to crack. Should I worry/

I always worry when I have to do a job like that, I try doing both side at the same time,you could also use a pipe freezing kit. Good luck

I always worry when I have to do a job like that, I try doing both side at the same time,you could also use a pipe freezing kit. good luck

I am a rookey. I notice such kits are very costly. I also don't understand how freezing the pipe would make a sweating operation work?

Part of my problem draining the pipe now, after I have made the first sweat, is difficult and time comsuming.

I wondering is heating one side of value will slowly heat the water side and therefore not crack the pipe. But it does worry me.

thanks for your reply

There's some real plumber around here somewhere, they'll give plenty of good advice. Hang in there

Is there a problem that you can't shut off the water and you can't drain the water?

I don't see a problem with the way you are trying to do I am sure it will work, but I have not done it, please wait when all other expert gets online will advise what to do, I just returned from a long trip and still having the jetlag, Thanks.

John

When you solder copper the heat will travel up the pipe. We call that "convection".
You have a 1/2" pipe filled with cold water 3/4" away from the joint you're attempting to solder. We call that a "heat sink" because it will suck the heat right out of your valve as fast as your torch can heat it.
Shut the water off at the house stop and open up the gate valve to drain the line.
Leave the valve in the open position. Now take your torch and run your flame back and forth over about 6 to 8 inches on the bottom of the pipe. Stop heating the pipe when steam stops coming out. Now you're ready to solder.
Some plumberrs recommend stuffing dried bread up the pipe to soak uo the water. I'm not one of them. Good luck, Tom

Yes, we have done this many times before with 100% success. We did not have any problem with rupturing valves, yet. I understand you worries, but I would say:... if you cannot close water coming to the valve, than go for it.

Wet vac's also work. The bread trick is an old plumbers one.

Solder with the valve fully open and the packing nut a little loose. Tighten the packing nut after soldering.

Yes, we have done this many times before with 100% success. We did not have any problem with rupturing valves, yet. I understand you worries, but I would say:... if you cannot close water coming to the valve, than go for it.
Miulo and I don't disagree very often but this is one of those times for the reasons I've given above. If Milo's come up with a way to solder a joint with a pipe full of water I want to know about it.

Tom, there is a closed valve in between. I agree with you: the best way is to drain the pipe - but yes, you can solder pipe into the other end of a closed valve. I have done it personally few times...

Yep, but not a rookie operation.

In replacing water heaters that are connected with sordered copper fittings and have a cuttoff valve I always just turn the valve off and do any soldering that I want to do on the valve and I don't have a problem unless the valve is leaking water through and then I turn off the water and drain it down to replace the valve.

And yes I am one of those that have used bread when soldering, not to soak up the water in the pipe but to keep the water from dribbling down to where I am soldering.

Tom, there is a closed valve in between. I agree with you: the best way is to drain the pipe - but yes, you can solder pipe into the other end of a closed valve. I have done it personally few tiimes
Can you say. "Cold solder joint"? You have the end of the pipe that you want to melt solder and form a joiint less the 3/8ths of a inch of a pipe filled with cold water. I've never attempted this but if you say it can be done I believe you. Regards, Tom