The Joy of Undocumented Features

The old water mixer in my darkroom, which looked like it dated from Ronald Reagan's first administration, was on its last legs. So, I decided to make and install a new one.

Here was my plan.

Buying the parts was straightforward. A test assembly showed that the inlet and outlet points of the new mixer lined up perfectly with the existing segments of copper tubing that provided hot, cold, and mixed water.

Then disaster struck.

As I was assembling all the components with teflon tape, I discovered that one of the valves would no longer connect to the rest of the assembly. I rechecked the packages the valves came in, but they were all labled the same with specifications for the correct size and type of screw threads.

Puzzled, I called the toll-free support line listed on the package the valve came in, relieved that at least some plumbing supply companies still provide toll-free technical support. After waiting on hold for about fifteen minutes (while being repeatedly assured that my call was important and would be answered in the order in which it was received,) I spoke to a friendly first-tier support analyst.

I explained the problem: Whenever I tried connecting this one particular water valve to the rest of the water mixer assembly with teflon tape on the screw threads, it just wouldn't connect properly. But, it connected fine if I was not using teflon tape.

He first asked me to be sure the revision level of the valves all matched (remember, I was assembling a water mixer with three valves,) and that the valves were all at the most recent revision level from the factory.

Since all the revision levels matched, the support analyst suggested I try each of the following procedures:

• Opening and closing the water valve with the teflon tape on it.
• Putting the valve back into it's original packaging then removing it again and reconnecting it.
• Assembling the whole water mixer without teflon tape, then removing and applying teflon tape to the components one at a time, starting with the component farthest from the valve that was giving me problems.
• Rapping the valve on a hard surface several times.

He said that hopefully one of these would reset the water valve's automatic thread configuration setting. The particular valves I bought should only be reconfigurable when connected to a computer running the proper software, but that the versions I bought had static configurations. The valve in question shouldn't have reconfigured itself for different thread sizes and pitches, but that had been known to happen spontaneously. Usually, one of those four procedures would reset the valve to the desired thread configuration, but if they didn't work he advised me to call back and there were more elaborate diagnostics they could run on the water valve, including sending me a diagnostic CD that could probe the water valve's register settings.

Unfortunately, none of his suggestions worked, but his mention of an automatic thread configuration setting on the water valve got me to thinking that perhaps I'd stumbled onto an obscure, undocumented feature in the user interface of the water valve. Perhaps I'd accidentally enabled some automatic configuration setting.

After downloading the 480 page Water Valve Administration Guide from the manufacturer's Web site, I found out how to disable a feature called automatic thread switching, in which the valve's threads change automatically depending upon how the it's being used.

I read the instructions and was able to disable this automatic feature. After that, the valve connected just fine and I now have a brand-spanking-new water mixer in my darkroom.

It's times like those that make me seriously consider switching to a computer for my fine-art printing.