Extend Water Heater Value Drain Line to Minimize Property Damage

Longer Line Creates Need for Less Expensive Piping Materials

Despite its important function of providing warm water every day for everything from showers to laundry, the hot water heater is one of the most neglected and often overlooked appliances in the home. In fact, most people might forget it’s even there until, of course, it stops working or there’s a problem with water damage.

All water heaters are designed with a discharge line (also known as a blow pipe) that hangs to the side of the unit. Its purpose is to carry water away from the heater to a safer, more appropriate outlet. During the heating cycle, water expands inside the heater. A pressure relief valve protects against excessive pressures and temperatures by directing water through the discharge line to an outlet.

Since the discharged water is often scalding hot, it is critical to direct it away from human contact, as well as electrical parts and other materials that can be damaged by water. In homes without basements, the discharge line typically runs outside to minimize property damage. Historically, however, homes with basements have had a shorter blow pipe that discharges to a nearby drain in the basement floor.

With more homes today having finished basements, though, the need for an extended blow line has increased significantly. A 2005 survey of architects showed that 50 percent of the industry is seeing a definite growth in the number of finished basements and attics.

As more homeowners seek to maximize living space, basements today are often also serving as playrooms, home offices, guest suites, workout rooms, or home theatres rather than simply storage space. On top of this trend is the growing popularity of one-story homes with no basements caused, in part, by cash-strapped homeowners who can’t afford the construction costs of a basement, or aging baby boomers who prefer to live on one level without steps.

When combined, these two building trends translate into fewer places to safely discharge hot water inside the home. As a result, many plumbers now recommend that the water heater blow pipe be extended to allow for safe discharge of water outside the home. That means the once four-foot-average length line is now more likely to be 25 or more feet in length to reach the nearest egress.

With this type of increase comes a noticeable difference in the pocketbook, especially with skyrocketing copper prices that have nearly doubled in the past two years alone with no relief in sight. Fortunately for cost-conscious homebuyers, there are more cost-effective alternatives to copper that are approved for discharge line use, including several plastic piping materials such as CPVC (chlorinated polyvinyl chloride).

Regular PVC pipe cannot handle the high water temperature. FlowGuard Gold CPVC is rated for 100 psi at 180°F. And since the pressure for a discharge pipe that’s open to the atmosphere is nearly 0 psi, the FlowGuard Gold CPVC pipe has been tested and proven to withstand the higher temperature of 210°F. (Water heater temperature relief valves are typically set to open at 210°F.) And that’s why CPVC is accepted for this application by all major model plumbing codes, including the Standard Plumbing Code.

CPVC offers the additional advantage of 100 percent corrosion resistance, which makes it highly reliable, especially in aggressive hot water applications. But most important if you do decide to safeguard your home and its contents from water damage and extend your discharge line is the cost savings afforded by CPVC.

Unlike metals such as copper, CPVC is not a limited natural resource subject to market pricing fluctuations that result from unstable foreign demand. In the past six years CPVC prices have remained stable.