I have a corroded soft copper tube (Type M?) hot water line that is laying on the ground in a short crawl space under the kitchen floor. I think the line corroded because it contacted the soil rather than being hung from the joists. I want to repair the line. I cut a hole in the kitchen floor to expose the work area. The defect is corrosion pinholing.
The first fix I tried was to cut out a generous amount around the defect and then splice in new Type L with 2 compression fittings on either end. That did not work - probably because the soft copper tubing had reduced OD and wasn't "snuggable" in the compression fitting.
Next, I tried sweating in some couplers to a new splice. That did not work; I had small partial failures at the joints. I had cleaned (sandpaper) especially well (but obviously not well enough). I also fluxed/pre-wetted the old ends by heating and flowing and then wiping away the solder so as to keep it fairly thin. The old ends, when sweating, just didn't flow like new. The joints to the new piece was just fine.
Is there a particular technique to super clean old work? Is there a different repair technique altogether?
Replacing the whole line is cost prohibitive - mostly because of collateral damage to open up walls. I would likely go "above" (attic) to run the new lines.
Can anyone help with a repair technique?
Thanks. John