Another Disagreement on Relief Valve Discharge

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By Barry Stone

Dear Barry,

There seems to be some confusion regarding where to terminate the discharge pipe for a water heater that is in a garage. Some say that the garage floor is OK, while others say the pipe should end outside. What do you say? - Ken

Dear Ken,

All water heaters require a relief valve, designed to release steam and hot water in the event of overheating or excess pressure. In the old days, before relief valves were required, excessive heat or pressure could cause a water heater to explode.

The question now is where the steam and water released by the valve should be allowed to drain. The first concern is to ensure that it does not spray on persons standing nearby. Thus, a discharge pipe is required to convey expelled moisture to a safe location. The original requirement was simply to terminate the pipe within 24 inches of the floor, which addresses the question of safety. The next issue to arise, however, involved protecting the property from water damage.

According to current plumbing standards in most areas, the discharge pipe should extend to the exterior of the building. However, some codes also state that the pipe may terminate at an "approved location." Unfortunately, various building departments are not in agreement as to interpretations of that phrase. Some approve termination inside a garage; others insist on exterior termination.

Where such debates occur, a wise approach is to consider the intent of the code. In this case, the main idea is to prevent moisture damage to the interior of the building and to its contents. Since garages are commonly used as storage facilities for personal property, water on the garage floor can have costly consequences. If draining to the exterior of the building is not practical or acceptable, alternate approved locations could include laundry sinks, drain standpipes or floor drains. Some building departments, however, have decided that termination at a garage floor is acceptable. Although we may disagree with that interpretation, each building authority exercises absolute judgment in its jurisdiction. By self-definition, bureaucracies are always right, even when they're wrong.