What to Know About Water Losses Associated with Failed Metal Plumbing Components

All plumbers worth their salt have heard that paste flux, used in soldering, causes pinhole leaks in copper pipe. While plumbers may have heard this, not all believe it is a major issue. As a result, the care associated with the use of flux can sometimes be less than what the situation requires.

Flux is used to facilitate a bond between the solder and the copper when soldering (“sweating”) a joint. Anyone who has ever watched a plumber sweat copper pipes would have seen them use flux and possibly noticed that flux residue covered the plumber’s hands, gloves, tools and toolbox. The manufacturers of paste flux provide warnings on the containers of their product that indicate the flux is corrosive and should be washed off after soldering to prevent corrosion. Paste flux manufacturers go on to state that flux is not for use with aluminum, stainless steel or magnesium.

The issue presented in the industry occurs when flux and stainless steel clamps used to connect cross-linked polyethylene (PEX) tubing come in contact.

PEX is commonly known as a plastic alternative to copper pipes in domestic water applications. This type of plumbing system has gained significant popularity during the last 10 to 15 years among homebuilders and plumbers because of the potential savings. These stainless steel clamps are intended to secure the PEX tubing on the barbed fittings located at each end of the tubing. The fittings are typically made of brass or plastic and are used to join multiple sections of the tubing or to transition to another material type or fixture. The clamp, when properly installed, provides a uniform compression and a 360-degree sealing surface by incorporating a tongue-and-groove design at the clamp’s overlap.

A problem occurs if the clamp fractures transversely across its band. Such a failure releases the clamp’s compressive force and allows water to leak between the barb fitting and PEX tubing interface.

The typical failure of the stainless steel clamp is due to a process called stress corrosion cracking (SCC). In most cases, the corrosion is driven by exposure to some form of chlorine.

Engineers and other experts have debated whether the presence of chlorine on the fitting is from the residual chlorine found in most municipal water supplies. However, the concentration levels of chlorine on the failed fittings are generally found to be much higher than are expected in municipal water supplies and suggest the failure did not result simply from exposure to water.

Alternatively, traces of another corrosion-producing substance are also often discovered, which indicates the presence of flux.

Failures generally occur on the hot water supply piping and the failed clamp is often connected to a copper adapter fitting. More specifically, this adapter fitting is the point where copper pipes transition to PEX. Therefore, one side of the fitting has a soldered joint, and the other side uses the stainless steel clamp. The increased temperature of the water accelerates the rate of corrosion.

So, in review, the failure occurs immediately adjacent to a soldered fitting that uses flux, flux is corrosive to stainless steel and elements consistent with flux are found on the failed clamp.

Who is responsible for the failure? The plumber should have a certain awareness of the flux’s corrosive nature, but the manufacturer of the stainless steel clamp should be aware that the clamp will be used in close proximity to a soldered joint.

Implications of this problem can be quite severe in situations where multiple clamps become contaminated due to handling and/or storage on a plumber’s truck. These connections are hidden in walls, floors and ceilings throughout a PEX plumbing system.

Take, for instance, a small two-bathroom house. It could easily have more than 25 of these fittings installed. Large houses could have more than 100 fittings, depending on the number of plumbing fixtures and turns in the piping.

Stress corrosion cracking is not an isolated problem with stainless steel PEX clamps. In the plumbing industry, it is also the mode of failure for numerous stainless steel braided supply lines and most brittle brass failures. A commonality in most cases is that a driving corrosive is present.

For the PEX clamps, the corrosive is the flux, and, for the stainless steel braided supply lines, the corrosive is chlorides found in household cleaners. In either situation, the manufacturer can implement design changes to make the product more robust to the effects of SCC.

Take, for instance, the design changes in Fluidmaster and BrassCraft Manufacturing supply lines. The stainless steel braid on new Fluidmaster supply lines can fail completely by corrosion; however, it will still not cause a catastrophic water loss. BrassCraft has altered the materials in the design to remove stainless steel completely from the supply line.

Now, the thing to be looking for is how the industry will react to the failures of the PEX clamps. Often, the first reaction is to simply create a warning to increase the awareness of the problem. If the problem continues, then alternative designs will be developed, assuming it makes financial sense.

In the meantime, it’s important to document the losses and secure evidence in order to build strong subrogation cases.

Keys to building a strong case are to document, photographically or otherwise, the details specific to the failure mode and analyze the failure of the clamps in a laboratory. Failure mode details include:

• Was it on a hot water supply?
• Was it used in close proximity to a copper fitting?
• Who installed it?
• How long has it been installed?

This documentation will provide investigators, whether at the scene or in a laboratory, the tools necessary to identify the party responsible for the failure.