Under ground copper soldering

When I've sweated new copper fittings onto existing 'in ground' copper the results are poor. Even cleaning the tube extreamly well and with good preheat, the results are usually bad. Is there some chemical reaction that happens to the copper after it's been in the ground? How do I sweat these joints?

copper

The copper pipe and fittings have to be super clean, shiney and dry.

There may be microscopic pitting of the surface. Brazing the joint should work.

As far as I know the only soder approved for burial / underground use is silver soder.

Brazing is also approved.

Regular soder will work but not well and will fail sooner or later.

No amount of cleaning or prep will make a difference with standard soder.

tinning flux

if you are going to solder something to make
repiars or connect to something to
pipes thar have been under ground It might be
good to use some sort of tinning flux to give you
an edje over the lime and calisification that natrually
builds up on the outside of the pipe...


like others said its got to be sanded and throughly
cleaned down to the bone, or it will fail....