Black flakes from faucet signal corrosion

  • By the Carey Brothers
  • Wednesday, April 11, 2012 11:56am
  • Life

It is rare for us when we get a question that is so thoroughly detailed. One of our listeners emailed us with the following question:

“We have fine, black flakes that occasionally come out of our kitchen faucet. It is the only faucet in our home with this problem.

“The flakes generally come from the hot water side but do occasionally appear in the cold water side.

“Our pipes are all copper. We replaced washers in the faucet, but the problem has persisted. What do we do?”

First, we had to diagnose the problem:

Only one fixture was affected (this localizes our search to the components that serve only the fixture in question).

Next we had to determine which elements were capable of generating a black residue (a disintegrating washer is only one source).

We looked to another common source that can produce a black residue (a corroded galvanized iron pipe is capable of producing black particles “flakes”).

But the pipes were reported as being copper (when copper corrodes the residue is green not black).

Even so, black residue usually means that galvanized-iron is present. Fortunately, we know that older copper systems terminate at the fixture location with a galvanized-iron fitting. The one that protrudes through the wall (we felt we had discovered the source of the black residue).

The cause of the corrosion is very common in older systems. Electrolysis occurs when dissimilar metals come into contact with each other (in this case copper and galvanized iron).

The fact that the problem was more severe on the hot water side had little bearing on our analysis (corrosion, no matter what the cause, occurs more rapidly at higher temperatures).

Electrolysis between copper and galvanized iron manifests itself as corrosion on the inside surface of the galvanized pipe. The corrosion that builds up is usually black in color. Ergo, we have our second source of black flakes.

Left unchecked, the corrosion can continue until the galvanized pipe completely dissolves. The flood that follows can cause thousands of dollars worth of damage.

The repair can be made by using a special fitting known as a plastic coated nipple (a short length of pipe). The plastic coating on the inside surface of the nipple prevents electrolysis. Thus, the pipe will remain open and clear for decades.

To replace the short section of pipe follow these instructions:

• First, turn off the main valve the supplies water to the house.

• Remove the water supply line from the angle-stop that connects to the faucet.

• With a bowl or bucket beneath, slowly turn on the angle-stop to drain water from the line.

• When the water is drained remove the angle-stop with a pipe wrench by turning it in a counterclockwise direction.

• Next, remove the old nipple by turning it in a counterclockwise direction.

• Reinstall the new nipples by performing the removal process in reverse. Be sure to use joint compound or plastic tape on the treads of the nipple to insure a water tight connection.

Remember, you are dealing with a denigrated fitting. As such the nipple may disintegrate upon removal. If this happens you would need to use a tool known as an “easy out” to remove the balance of the fitting. The easy-out fits into the inside of the pipe. A tool that is especially handy when a pipe breaks at a connection. We hope you won’t need one. But be prepared.

For tips from James and Morris Carey, go to or call the listener hot line, 800-737-2474, ext. 59. The Careys are also on KRKO (1380-AM) from 6 to 10 a.m. every Saturday.

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