A reader from Ruxton wrote to ask advice about the water supply pipes in his house.
The house was originally fitted with galvanized pipe, and over the years some have been replaced with copper supply pipes, presumably due to pinhole leaks. He wanted to know if an inspector would classify mixed types of materials in a system as a problem.
Galvanized steel pipe was used from the early 1900s until around the end of World War II because it was a reasonably priced, available and durable material.
Galvanization, a process that coats steel with zinc, was performed to protect the inside of the pipe from rusting when in contact with water. But, as with most materials in the home, galvanized pipe does have a limited life. Pressure problems or leakage can develop after 40 to 60 years.
The zinc coating becomes depleted and the interior rusts, leading to clogging and reduced pressure. Pinhole leaks eventually develop. Temporary patching will delay a replacement of the pipe, but often inadequate pressure makes pipe replacement necessary before pinholes become a problem.
Galvanized steel pipe is typically replaced with copper piping or CPVC (Chlorinated Poly-Vinyl Chloride) plastic pipe.
CPVC, similar to PVC used in waste pipes, is able to handle the higher temperatures and stronger water pressure found in supply pipes. The cost of materials when replacing galvanized steel pipe with CPVC pipe typically is less than that of copper.
If copper pipe is installed in a house with well water, a neutralizer may be necessary to prevent corrosion if the water is excessively acidic. Also, if copper pipe is connected to galvanized pipe, the joint is subject to deterioration due to galvanic action. Specialized fittings or dielectric tapes normally are used at such connections.
It is quite typical to find different materials side by side in one system as repairs have been made over the years. This is not a concern as long as the materials are properly installed and in functional condition.
In reality, it indicates that a homeowner has addressed maintenance issues and has updated system components, albeit on an as-needed basis.