The majority of mobile-home manufacturers use soft copper tubing for fresh-water lines. It’s flexible and easy to use. But, because of its pliancy, it is susceptible to punctures and pinches from nails or staples in the framing. When these punctures bring on leaks, repair them.
You need these supplies: tubing cutter, propane torch, emery cloth, flux, solder, and copper unions. Turn off the water at the main shutoff valve. Open the faucet nearest the leak, to empty the line. If the line hangs horizontal, support it so its weight doesn’t drag a fixture out of alignment.
Remove the punctured portion with a tubing cutter or hacksaw. (Page 68 shows how to use a cutter.) Deburr the tubing with the pointed attachment on the tubing cutter or with emery cloth. Measure the section removed, and buy a replacement length. Also purchase two threaded slip-on copper unions of a size to fit the tubing diameter.
Work in a well ventilated area. Clean oxidation from the ends of the tubing and from inside the unions with emery cloth. Slip one union over two ends of the tubing. Light the propane torch and heat the joint. Apply flux. As the flux melts, it cleans the metal even further, enabling solder to adhere properly. Apply solder to both ends of the union. It should flow on and into the joint quite readily. Seal the joint thoroughly.
Allow the tubing to cool. Then use the other union to splice the loose end of new tubing back into the line. Clean both tubing and union. The same heat/flux/solder technique seals the joint.
If the puncture is small, and very little of the tubing damaged, merely saw through right at the puncture. Deburr and clean both of the ends thus formed. You need only one union and no extra tubing, Just spread the tubing ends apart and work them into the union, Then heat, apply flux, and solder the joint. Check for leaks only after the joint cools a bit.