Air and vacuum relief valves should be located at high points and blowoff valves should be located at low points in the distribution system. Which statement describes their placement?

• A. Air and vacuum relief valves should be at high points; blowoff valves at low points
• B. Blowoff valves should be at high points; air and vacuum relief valves at low points
• C. Air release valves at midpoints; check valve at high points
• D. Vacuum relief valves only at all points

Answer: (A)

Vent air management and drainage are the guiding ideas. Air and vacuum relief valves are placed at high points because air naturally collects up top and these valves need to vent trapped air and allow air to enter when pressure drops during draining to prevent pipe collapse. Blowoff valves are placed at low points so water can be drained and the line flushed effectively, with gravity helping the purge. If a blowoff were at a high point, it wouldn’t drain the system well; if air or vacuum relief valves were placed at low points, they wouldn’t function to vent air where it tends to accumulate or admit air during depressurization. So positioning air and vacuum relief valves at high points and blowoff valves at low points is the correct approach.