Circulation pumps for hot water can shorten life of pipes
Q. During the past year, our hot water pipes have developed four leaks under the house. With each occurrence, the ground area below the building has become soaked, causing moisture damage to the subfloor. The plumber who repaired the leaks found small holes in the copper elbows, and he blamed the circulation pump on our water heater.
How could this have happened in a custom home that is only seven years old, and what can we do to resolve it?
A. Circulating hot water systems have become increasingly popular in recent years because they eliminate the inconvenience of waiting for hot water to arrive at the faucets. Most circulating systems function for many years without any major problems, but in some cases, microscopic air bubbles in the water supply can cause erosion of the internal pipe surfaces, resulting in eventual leakage, especially at the pipe elbows.
This problem occurs most often in hot water systems that have high-velocity circulating pumps. High-speed pumps often create a churning effect, causing the air molecules in the water to spin. These minute bubbles act as abrasive particles against the pipe surfaces, as if a sand storm were occurring within the water lines.
Plumbers who install circulating systems are advised to use low-speed pumps wherever possible. Another preventive measure would be to install heavier-gauge water pipes. Residential water lines typically consist of type M copper. When circulating pumps are installed, type L or type K pipes, which are thicker gauges of copper, are advised to prevent wear and leaks.
Another alternative is to use PEX plastic pipe, which has become the material of choice in most new residential construction.
Now that your plumbing system is worn and prone to leakage, it may be necessary to replace all of the hot water pipes. This will have to be determined by your plumber.
Q. A home inspector recently cited my garage for lack of air vents, stating that vents are needed because the gas-burning water heater and furnace are located in the garage. Yet, according to my contractor friend, garage vents are not required, even when gas appliances are installed. Who's right?
A. Screened vent openings are often installed in garages, but they are not required by code, even when gas-burning fixtures are present. People are often surprised when garage vents are omitted, because vents are typically found in older garages. In newer garages, vents are typically omitted, because the current trend is to finish garage interiors with drywall.
The original intent for installing garage vents was not to provide combustion air for gas appliances, but rather to enable car exhaust and gasoline fumes to escape. These reasons would seem to warrant an active code requirement, but none has ever been enacted.
According to applicable codes, air openings are only required for gas fixtures when the volume of the room or enclosure is less than 50 cubic feet per 1000 BTU's. In most cases, garages are large enough to accommodate this requirement, especially because garages are not tightly constructed. In most cases, the loose openings around garage doors will allow adequate air infiltration for gas fixtures.
• 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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