soldering copper pipe

[David Rose]

The silver bearing solder that I planned to use to join my shop air copper pipe uses zinc chloride for a flux. Zinc chloride is a mild Lewis acid... according to the net. Acid flux is not recommended for copper air line usually. Should I change solders? This is a low temp (good), high strength (good) solder, and I have an ample supply.

Btw, the flux is very water soluble, but I hate to put water through new lines that haven't even had air yet!
Just kidding... but I don't know if that would help.

David

[Del Williams]

David - It seems that the Zn+ Lewis acid species is a fairly low reactvity acid. In reality, it probalby will not be an issue for you. Since the flux is readily water soluble, do a wet rag wipe of the solder joint after you finish and charge ahead!

[David Rose]

Del, I can't do much to the inside. From what you say though, it sounds like I will be OK. I'll go for it unless someone else talks me out of it... very quickly. I hate having so many opinions from the net, when there is only one right answer... usually, often, sometimes.

I'll get the pipe tomorrow evening and get started.

Thanks,

David

David - It seems that the Zn+ Lewis acid species is a fairly low reactvity acid. In reality, it probalby will not be an issue for you. Since the flux is readily water soluble, do a wet rag wipe of the solder joint after you finish and charge ahead!

[Bruce Shiverdecker]

If you really don't want to use the acid, look for Rosin core solder. This is used with electronics where you don't want acid. I've used it on water lines without problems, but have not put it under more that 50 pis.

Bruce

[Ben Grunow]

David- I have seen (in some architect's specifications for building a house) a description of flushing domestic water pipes with a solution of baking soda and water to remove the excess flux and associated taste. Never seen it done but maybe it would ease your concerns.

[Bruce Wrenn]

You mention silver bearing solder. That is generally considered silver soldering and is much more than needed for copper air lines. I would suggest that you use a lead free solder from Lowes or others and LACO flux. Lowes stores carry both Dutch Boy and Sterling brand solder. Both of them are made in the same plant in NC. You will probably have to go to plumbing supply house to get Laco flux. After making joints, wipe area with a wetted rag to clean excess flux and to prevent green goo that remains.

[Ken Garlock]

David, I would not be concerned.

Plumbers use acid core solder, and acid based flux all the time. Consider that the flux is just there to clean the surface of the copper so that the solder flows nicely and makes a good connection to the copper. By the time you get the pipe up to temp with your propane torch, you will never know that the flux was ever there, as it will be totally boiled way.

When I did my copper air lines, I bought a bottle of Ruby Fluid flux from McMaster & Carr. It is a non-acid based flux. I bought it because it was cheap....

[Carl Crout]

You mention silver bearing solder. That is generally considered silver soldering and is much more than needed for copper air lines. I would suggest that you use a lead free solder from Lowes or others and LACO flux. Lowes stores carry both Dutch Boy and Sterling brand solder. Both of them are made in the same plant in NC. You will probably have to go to plumbing supply house to get Laco flux. After making joints, wipe area with a wetted rag to clean excess flux and to prevent green goo that remains.

Actually silfloss is stronger than regular solder. Electronics solder is NOT designed for strength. You want to use silfloss.

Silver Solder (SILFLOSS) - Solder composed of silver, copper and zinc. Has a melting point lower than pure silver, but higher than lead-tin solder.

[David Rose]

Carl, I don't remember the psi, but the solder I have in abundance is called "Force 44" and contains some silver but no lead. It is suppose to be something like 10x the psi of normal lead solder. The temp is lower too at about 450 degrees. That is way lower than true silver solder and even most lead/tin solders. It is really easy to work with and flows well. It may very well be the same as Silfloss under a trade name.

David

Actually silfloss is stronger than regular solder. Electronics solder is NOT designed for strength. You want to use silfloss.

Silver Solder (SILFLOSS) - Solder composed of silver, copper and zinc. Has a melting point lower than pure silver, but higher than lead-tin solder.

[David Rose]

I thought plumbers were using acid flux... It just cleaned toooo well.

David

David, I would not be concerned.

Plumbers use acid core solder, and acid based flux all the time. Consider that the flux is just there to clean the surface of the copper so that the solder flows nicely and makes a good connection to the copper. By the time you get the pipe up to temp with your propane torch, you will never know that the flux was ever there, as it will be totally boiled way.

When I did my copper air lines, I bought a bottle of Ruby Fluid flux from McMaster & Carr. It is a non-acid based flux. I bought it because it was cheap....

[Charlie Hans]

David if you go with silfoss there is no flux needed, in A/C work no flux is ever used due to contamination of the system and the silfoss is overkill in my personal opinion unless you are running over 200psi, Lead free solder is very adequate for the job.
Charlie

[David Rose]

Bruce, I don't remember the numbers, but the percent has to be a certain level to be called silver solder. The stuff I have is only something like 2%, which only allows a claim of "silver bearing".

David

You mention silver bearing solder. That is generally considered silver soldering and is much more than needed for copper air lines. I would suggest that you use a lead free solder from Lowes or others and LACO flux. Lowes stores carry both Dutch Boy and Sterling brand solder. Both of them are made in the same plant in NC. You will probably have to go to plumbing supply house to get Laco flux. After making joints, wipe area with a wetted rag to clean excess flux and to prevent green goo that remains.

[David Rose]

Charlie, I needed to seal the ends of flattened copper tubing on an old AC unit that my Dad contributed to me for storage until one of our units fails. My local AC man contributed a stick of something about a foot long that was flat and used no flux. I didn't check the markings on it, but I'll be now that it was Silfoss. It was a higher temp solder than Force 44. It did work well when I got the tubing temp up. And I'll bet it was much more expensive. It appeared to be the color of silver solder instead of the flat gray color of standard solder (or the Force 44). I have enough of the Force 44 to plumb my shop a few times and then some (probably 3#). That is part of my reason for wanting to use it.

David

David if you go with silfoss there is no flux needed, in A/C work no flux is ever used due to contamination of the system and the silfoss is overkill in my personal opinion unless you are running over 200psi, Lead free solder is very adequate for the job.
Charlie

[Randy Meijer]

What most folks refer to as "silver soldering" is actually silver brazing. Silver brazing uses a braze alloy of copper and silver and other trace metals. The silver content can vary quite a bit; but the most common sticks are probably between 20-40%. Silver brazing requires a temperature in the neighborhood of 1200°F and produces an extremely strong joint.

Soldering, on the other hand, is done in a heat range of 350-500°F and uses an alloy that is based on tin. The standard solder that everyone knows about is a tin/lead alloy. There are also no-lead and silver-bearing alloys. The silver-bearing solders generally are about 5% silver. Solder joints are not nearly so strong as brazed joints; but are more than adequate in proper applications.

Since home water systems may see pressures on the order of 100 PSI, I would assume that soldering the joints of a compressed air system would be adequately strong and silver brazing them would not be necessary.

[Ken Garlock]

I thought plumbers were using acid flux... It just cleaned toooo well.

David

Yes, David, my years of using "rosin CORE" solder made me write acid core. (the devil made me do it ) There is acid core solder, but my plumber used the stuff you apply with a brush. The 'famous' glue brushes most of use are also called acid brushes. In any event, the time the acid is on the pipe isn't long enough to do more than clean the pipe. It certainly isn't like you are putting a combination of nitric + hydrofluoric on the pipe.