Advice for repair of corroded hot water line

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
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I'd replace it with plastic. CPVC or tube. Better get it all because if its leaking in 1 place it will leak in another later.
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Try again using compression fittings for flared pipe ends rather than using the ones with just ferrules. Probably need to buy a flaring tool too.
What size is the tube?

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J wrote:

It will just leak again in another spot even if you get a good connection to the replacement piece. Consider full replacement with PEX tubing since the flexibility of the PEX should let you fish it through walls with a minimum of openings.
Pete C.
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Yeah PEX is the way to go and real easy to work with!
DO IT RIGHT DO IT ONCE! Then go relax!:)
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snipped-for-privacy@aol.com wrote:

at any length. May have to rent crimping tool for couple hours. So.... easy!
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J wrote:

If I were you, I'd just splice in a length of Pemex(won't corrode). This may be easiest way. You may have to rent the crimping tool for half day or so. Solder in two adaptor fittings at both ends fit the Pemex over the fitting nipple, crimp. If you're soldering old pipe, clean well and make sure there is no moisture. Good luck,
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When you use compression fittings, it's wise to oil the nut, ferrule, and pipe before tightening. the oil (WD is ok, and 30 weight non detergent is good, too) lets the fitting slip and slide into shape. Sometimes a couple drops of oil makes all the difference, in getting a good seal.
--

Christopher A. Young
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