Home inspector: Water pipes make mysterious clanking

Q. The pipes in my walls make weird clanking noises. The place is about 15 years old, but I moved in recently. Whenever I wash the dishes or use the bathroom sink, I hear pounding sounds, like someone is punching the walls. And late every night, when all is quiet, I hear the same sounds, without even running the water. I know this is not normal because I’ve lived in many houses, and none of the others had this problem. What is going on in my home? Can I do something about it now, or do I have to wait for some kind of catastrophe?

A. The knocking sounds in your walls do not portend a catastrophe. These noises typically occur when pipes are expanding and contracting in response to temperature changes. When you wash the dishes or use the bathroom sink, hot water runs through the cold pipes, causing them to expand. Late at night, the coolness of the evening causes the pipes to contract.

When pipes are loosely fitted in the wall framing, movement can occur without noticeable sounds. When the pipes in the walls are tightly fitted, as is probably the case in your home, expansion and contraction can cause noises as the pipes move against the wood framing.

To correct this problem, drywall will have to be removed from some walls to provide access to the troubled areas. At worst, the problem is a nuisance, rather than a warning of worse things to come. If you are unable to bear the noises, have a licensed plumber give you a bid for repairs.

Q. Our home is about 12 years old and has radiant heat tubing in the concrete slab floor. We’ve discovered slab cracks in the floor tiles and some of the grout lines and are afraid the hot water pipes in the slab will also crack and cause leaks in the house. If that happens, we’ll have to replace the entire slab. Are the people who sold us the house four years ago still liable, and should we notify our homeowners insurance company about a potential flooding problem?

A. If the cracks are less than one-eighth inch wide, they are most likely typical stress cracks caused by concrete shrinkage or by expansive soil. Cracks of this kind are present in most slabs but are usually not visible through floor coverings, except tile floors, of course.

When ceramic tiles are installed without a slip sheet on the slab, hairline stress cracks in the slab can appear in the tiles and grout lines. Radiant heat tubes are unlikely to be affected because they have sufficient flexibility to accommodate normal cracks and stresses. If you haven’t had any leaks so far, there is probably no basis for worry.

Without a history of leakage, there is no reason to raise this issue with the previous owners, especially after four years. As for notifying your insurance company, your insurance agent should advise you in that regard.

Ÿ Email questions to Barry Stone through his website, housedetective.com, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.

$PHOTOCREDIT_ON$Access Media Group$PHOTOCREDIT_OFF$