Can underground copper pipe connections be soldered or should they be braised?

Answer 1

Until one or more licensed Plumbers contribute, I'll give it a shot. I suspect that local Plumbing codes will specify which is accecptable. So, temporarily, my opinion follows. Over the last 50 years, I have lived in three houses, all of which were/are 50 years or older. They all had 3/4 inch rigid copper water supply pipe systems, and all jionts were made with solder, including the underground service entrance lines. In my 64 years, I can recall only 5 leak failures, none of which were related to the soldered joints. Two leak failures in one house were due to the use of galvanized steel yard hydrant risers from the underground copper. The leaks occured at the bare steel where the galvanize was removed in cutting threads on the riser pipes, and in addition, the soil in that area was extremely acidic, and highly corrosive, resulting in "electrolysis" eating holes through at the threaded joint between the copper and galvanized steel. The second house developed leaks, three times, in the underground service entrance line, and analysis indicated that they were far from and not related to the soldered joints. Microscopic analysis of the holes, revealed that the holes developed from flaws in the pipe wall related to microscopic iron which got into the pipe wall during manufacture. It is interesting that it took 54 years for the flaws to corrode away, resulting in leaks. So, unless there is a code prohibition of solder joints in copper pipe for underground use, I suggest that soldering is fine, and braising would be an expensive overkill.j3h.

Answer 2

Underground copper pipe connections should be brazed rather than soldered. Brazing creates a stronger and more reliable joint that can withstand the pressure and environmental conditions typically found in underground installations.