Soldering is in a state of (water-soluble) flux

March 1, 2001
There is possibly no branch of construction work which has undergone within the same given time such great changes of a far-reaching nature as plumbing construction. That passage appears in R. M. Starbucks 1907 book, Modern Plumbing Illustrated. Amazing how timeless his words are when applied to the trade today. Just look at the changes weve seen in the past several decades. Leaded joints became rubber

“There is possibly no branch of construction work which has undergone within the same given time such great changes of a far-reaching nature as plumbing construction.” That passage appears in R. M. Starbuck’s 1907 book, “Modern Plumbing Illustrated.” Amazing how timeless his words are when applied to the trade today.

Just look at the changes we’ve seen in the past several decades. Leaded joints became rubber gaskets. Fernco and no-hub couplings became accepted. Cast iron gave way to ABS and PVC piping for DWV applications. Fifty/fifty solder was outlawed in favor of lead-free products in potable water applications. CPVC and pex have made inroads with potable and hydronic applications where copper once ruled as king. Seven-, 5- and 3.5-gal. water closets were flushed in favor of 1.6-gal. models.

And now come changes to flux.

Let’s take a look at Starbuck’s 1919 book, “Practical Wrinkles.” “An excellent paste for soldering purposes can be made of one part by weight of chloride of zinc, and 16 parts of some grease as Vaseline, thoroughly mixed together. The chloride of zinc is known to every tinsmith, and is made by dissolving in muriatic acid, as much zinc as the acid will eat up.”

Fluxes were basically made up of organic chlorides, zinc, bromides, fluorides and ammonium chlorides mixed in a petroleum grease base. One of their properties was that they were corrosive to copper tubing to some extent, which helped clean the copper during the soft-soldering process.

Because of their corrosive properties, it was necessary to properly limit the amount of flux entering the joint and to thoroughly clean the exterior after soldering to avoid visible discoloration and a shabby appearance. Fluxes are needed to inhibit oxidation and provide a medium for the solder to flow freely into the joint via capillary action.

Before I go any further with this subject, let me state that I love copper tubing systems. When I walk into a mechanical room and observe the soldering work of another contractor, I can tell in a heartbeat how much pride he took in his workmanship. Those gleaming pipes with neatly wiped joints, installed plumb and level, speak volumes about the installer.

I’m hoarding several “antique” rolls of 50/50 solder in my desk drawer. I also have a pig of wiping solder as a paperweight. They serve to remind me of our history and that nothing remains the same. Some day, the lead police will come to take me away!

So now that we’ve finally completed the learning curve for lead-free solders, along comes this new twist in the evolution of plumbing: water-soluble fluxes.

We’ve been experimenting with these new fluxes in our shop and I wish I could say that they perform better than, or equal to, the petroleum-based fluxes, but I cannot. The plain and simple truth is that these new products will require your learning new habits.

Now is the time for you to obtain multiple free samples available through your local reps and suppliers and perform a comparative test in your shop where you can control the environment. The last place you’ll want to find out which one works best for you is when you’re under the gun on a contract that contains penalty clauses! I sincerely hope the copper industry isn’t shooting itself in the foot with these new products.

So, why this change? The Copper Development Association, working with the American Society of Testing and Materials, has developed astm B-813 for manufacturers of water-soluble flux. (Look for the B-813 listing on the label.) This was brought about as a result of copper pitting caused by the use of aggressive fluxes and, in my personal opinion, the misuse of those fluxes by the installers.

The proper technique was always to put a thin film of flux in the fitting, not gobs of it. We once had to clean out the copper tubing on a whirlpool tub because someone at the factory had stuffed about 20 lb. of flux in the distribution tubes. It left an ugly flux ring in the tub every time the owners used it.

The plain truth of the matter is that many of these new fluxes are more sensitive to heating within the temperature ranges to which we’ve become accustomed. They can burn away, leaving a residue and oxidation, resulting in leaks once the system is activated.

Some of these new fluxes begin to act upon application and do not allow you the luxury of delaying soldering once you’ve fluxed the joints.

Several contractors I’ve spoken with have indicated they might be inclined to dump out the water-soluble fluxes and place their old reliable flux into the new container to satisfy the inspectors, who are only able to verify compliance by checking the container label.

The consensus among them is that these fluxes work acceptably well on sizes under 2 in., but that sizes above that result in too many defective solder joints.

You can experiment by heating samples on bare copper tubing, without fittings, to compare temperature ranges and residues left behind.

There is one other concern that I have with these new flux products and that deals with the msds (Material Safety Data Sheets). Some of these newer products appear to be harsher than the old reliable fluxes and you should be checking the msds sheets for compliance. With a pH well below a neutral of 7, some of these fluxes can cause “aggressive” injuries to mucus membranes and eyes. It should go without saying that gloves and safety goggles need to be provided (and worn) by you and your employees.

Avoiding respiratory injuries requires either adequate ventilation or proper respirators when working in confined spaces.

“Avoid breathing vapor,” says the msds for one flux. “Use niosh-approved respirator where exposures exceed osha pels.”

One chilling admonition? “Provide showers and eye-wash station where used.” I have yet to see a new home construction site, much less a commercial one, with those safety measures in place.

Voice your opinion!

To join the conversation, and become an exclusive member of Contractor, create an account today!