Water heater relief valves shall be piped ____________________________________.

Water heater relief valves play a critical role in maintaining safety within a plumbing system by preventing excessive pressure build-up. The correct requirement is that these valves must be piped in a manner that allows for gravity flow, using the full size of the relief valve outlet. This ensures that any discharged water, especially if it is steam or hot water, can flow freely and is not impeded, reducing the risk of pressure causing failure or hazards.

Gravity flow is important because it relies on the natural force of gravity to direct potentially dangerous discharges to a safe place, minimizing the risk of the fluid coming into contact with personnel or causing damage to the building. Using the full size of the outlet also helps to prevent any bottlenecking that could occur if the pipe size were reduced, which could ultimately lead to improper functioning of the relief valve.

Not using bends unless increasing pipe size, nor directly connecting to the nearest waste line, can introduce complications such as air pockets or increase back pressure that could hinder the proper operation of the relief system, making gravity flow with the full size of the outlet the most effective and safest option.