Don't Over Tighten
Red White Valve technical adviser Mark Stanhke examines why valves can fail in residential applications.
Mark Stahnke, a part-time technical consultant for Red White Valve Corp., has been working in the plumbing industry for nearly 30 years. After completing his apprenticeship through Local 78 in Compton, Calif., he worked for Frank Snavely Plumbing, a residential-commercial service and repair contractor in San Pedro, Calif. To advance his career, he accepted a position with Norris Plumbing Fixtures as a customer service manager. (Mansfield Plumbing Products LLC acquired Norris in the early 1990s.) There, Stahnke handled defective product issues and studied failure analysis on a large scale. In essence, he became the company's firefighter as it related to fixture installations in new home construction, which included accompanying attorneys to inspections to evaluate installation problems. Stahnke became proficient at gathering information that the attorneys were unable to find on their own, and he was called regularly to provide expert witness testimony. In 1990, he left Norris to start his own consulting firm. Since then, he has worked on product and system failure analysis for insurance companies and law firms.
To broaden his knowledge of plumbing products, he accepted a position with Red White in 1999. Realizing the industry needed more information about why and how valves fail, Stahnke added an 18-page section to Red White's Web site (www.redwhitevalveusa.com), which explains and illustrates valve failures in particular applications.
Stahnke spoke to Reeves Journal about what contractors need to keep in mind in order to prevent valve problems during the installation process.
How can poor installation practices lead to valve failures?
Plumbers will typically over-tighten pipe nipples into the valve when there's a leak. They'll keep tightening to the point where the leak might stop, but by then, there won't be any more threads left. And the nipple will make contact with the valve's chamber wall. When the nipple pushes or compresses against the thread chamber wall, it distorts the internal valve mechanism.
On a gate valve, for example, when the nipple is over tightened to point that it pushes against the thread chamber, it distorts the chamber. On the other side is the valve seat. If the seat has been distorted, then the gate will not close properly. Typically, if the valve is installed with the gate in the closed position, the valve will lock up. In some of the extreme cases, the disc gets locked in the closed position and when the plumber tries to open it, the stem will coil.
A common solder valve failure occurs from over heating the valve during the soldering process. This happens when too much heat is applied to the valve. It can melt the valve seats, causing total seat failure. It can also cause the valve seal between the body and end piece to leak.
Can plumbing systems fail from the use of an improperly sized valve?
Yes. For example, a reduced port ball valve in a residential water distribution system can impair the system's balance by creating pressure drop across the valve. This can contribute to temperature escalation issues like when a water closet is flushed while somebody's taking a shower. An undersized valve can also create turbulence leading to downstream erosion. Under the UPC, a full port valve is required in residential potable water systems.
Another factor that leads to a faster system failure, especially with copper pipe, is that plumbers fail to ream the pipe before they join it. In litigation that I've been involved in, more times than not, the copper tubing was not reamed.
What percentage of copper tubing is not being reamed?
I would estimate that as a high as 40 percent of copper pipe is not being reamed. Usually it's one part of the system failure. It's generally discovered during destructive testing. Plumbers should be aware that there are attorneys who are looking for specific issues like this on which they can build a case.
Can aggressive water cause valves to fail?
Yes. I'm not a chemist, but aggressive (low pH, high CO2) water can usually be found in well water because it has a lot more soluable minerals. It accelerates corrosion not only in valves, but also in copper tubing. It accelerates the dezincification process, where the molecular chemistry of the valve changes. Materials have an anodic-cathodic relationship. The valve is made up of a percentage of copper and zinc and number of other metals, which make up the basis for the alloy. The anode would be the lead or zinc component and what happens is that the aggressive water draws the component out of the metals and allows the copper to be attacked. As a result, the stem often fails first.
However, I haven't seen very many valves come back with that problem. Over the years, manufacturers have developed alloys that are resistant to dezincification.
Can a failure occur if a soft-seated valve is subjected to an effluent that it's not designed for?
Yes. It will attack the valve seat material and cause it to expand or disintegrate.
If a contractor is inspecting a valve for defects, what should he or she be looking for?
Most manufacturing defects are visible. A casting hole in the valve is a common problem. A forging defect, where there wasn't enough material to complete the product is another issue. You can usually see a surface- to subsurface-level fracture. On the surface, you'd see a hairline fracture. On a subsurface fracture, you'd see a crease on the surface, but it hasn't opened up yet. It would look like a little wrinkle across the valve. This would indicate some type of forging material stress.
What contractors need to watch out for is in a soldered-type valve where the fitting cup has been distorted so it's slightly out of round. I've seen a couple of instances of this from the manufacturing end. The fitting cup damage is more often created from the valve receiving an impact from being dropped on the ground or tossed into a plumber's storage bin. After all, the brass or bronze is a relatively soft material alloy. As a result, you may have lost some of the capillary space reserved for the solder.
What has changed in the valve manufacturing process, which might affect the installation process?
We're seeing more Teflon packing washers. Teflon is a harder material. It doesn't compress like the graphite washers did. As a result, the packing nuts are breaking easier than they used to, which may need to be addressed from the manufacturing side. The top of the nut absorbs all the compression, and the valve will drip around the packing nut. The plumber will use a crescent wrench to tighten it until the drip stops. On some cases, the nut has been driven all the way down to the bottom of the threads on the valve bonnet.
"This article was originally posted on ww.reevesjournal.com."