Why old pipes remain after re-piping
Q. Our home was built in the 1950s, and all the original water pipes were galvanized steel. A few years ago, we hired a plumber to replace the old piping with copper. Now that we're selling the house, the buyer's home inspector says there are still some galvanized pipes in the building. I've looked in the crawl space and can see only copper. Do you think the inspector is making a mistake?
A. You should ask the home inspector where the galvanized steel pipes were found. There may be some old plumbing in places where you have not looked.
When an old house is re-piped, plumbers sometimes replace only the horizontal pipes beneath the building and leave the old vertical pipes that are inside the walls. The reason for a partial pipe replacement is to minimize the cost of re-piping. Pipes under the house are exposed and accessible. Pipes inside the walls are more difficult to access. Replacing them involves wall surgery and cosmetic repair work.
Replacing all of the old pipes is obviously the best approach because the pipes inside the walls will eventually become corroded and require replacement. However, the remaining galvanized pipes may still be functional.
When old steel pipes are badly rusted, water flow can be noticeably restricted. This is usually apparent when more than one plumbing fixture is being used. A practical test is to observe the shower flow when other plumbing fixtures are turned on. If a flushing toilet or an open faucet causes a significant volume reduction or temperature change at the shower, this is a sign of excessive corrosion inside the lines. If no flow changes occur, repairs are probably not necessary.
As a side note: Be sure to ask the home inspector if dielectric unions were installed where the copper pipes adjoin the old galvanized lines. Direct contact between pipes of dissimilar metals can cause accelerated corrosion due to electrolysis.
Q. The brick lining is coming loose inside my fireplace, and the house is only 12 years old. The mortar is simply crumbling. How could this be happening in a home that isn't very old?
A. There are two potential causes for the decomposed mortar in your fireplace. The mortar may have been improperly formulated when the bricks were installed. For example, whoever mixed the mortar may have used water or sand that was not clean. A more common cause, however, is the lack of a cap on the chimney top. Here is how that can happen:
Fireplace chimneys generally develop a coating of black residue, known as creosote, on the inner linings. This is why we hire chimney sweeps, to remove this deposit. When rain water mixes with creosote, a mild acid is formed. This solution gradually seeps into the masonry lining, neutralizing the alkaline chemistry that binds the mortar, causing it to weaken and disintegrate. To prevent this degenerative process, the installation of an approved chimney cap is advised to keep out rainwater. You should also have your fireplace and chimney inspected by a certified chimney sweep.
• To write to Barry Stone, visit him on the web at www.housedetective.com, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.
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