Silver Soldering Copper Pipe - Flux or no flux? 1

[umreng]

When silver soldering copper tubing, is it required or advisable to use a soldering flux. The application is a direct bury potable water supply line, size 2".

 

[Montemayor]

You are soldering copper pipe the right way, in my opinion, with silver solder. And never fail to employ the correct flux. Since I worked my way through college as a boilermaker and was trained as welder, I do my own soldering at home and for friends when I have a chance.

I would never accept a so-called solder joint done without the correct flux. The metals simple won't bond thoroughly due to a dirty amalgam surface. For a strong and dependable joint joint, you must insure complete cleanliness and pure, clean metal finish. Flux does this while the joint is being formed. Nothing else, in my experience will match this method for soldering strenth.

I used to do my own soldering in my plants because it has become rare to find experienced solders anymore. My personal soldering has been done on cryogenic equipment and coldbox piping. My joints were routinely tested to 5,000 psig on copper piping up to 1" size.

 

[trihydrate]

Yes, flux is required when silver soldering. It is also required when low temperature soldering.

Since you have asked if flux is required I must assume you have never tried soldering before. That leads me to ask if you need the additional benefits of silver soldering over the common low temperature solders.

There are incredible numbers of low temperature solder joints employed in direct burial of copper pipes compared to high temperature soldered joints.

If your are a novice, the cost, the equipment and the skills required to do low temperature soldering will be in your favor.

Good luck!

 

[hacksaw]

Most of the hardware store tin-silver solders come with their own flux. The flux is to keep the copper from oxidizing under heat and to assist in wetting.

If you are using solid core solder, be certain that lead-free wipe on flux is used.