Which of the following can cause loss of zone pressure?

• A. Leaking drain traps
• B. Leaking cable ways or stuffing tubes
• C. Open fittings
• D. All of the above

Answer: (D)

Maintaining zone pressure depends on keeping air from leaking between spaces. Any path that lets air move out of a pressurized zone or in from an adjacent space will reduce that pressure. A leaking drain trap creates an opening in the sanitary lines where air can escape or move into other areas, bypassing the seal and lowering zone pressure. Leaking cable ways or stuffing tubes provide large unintended openings through bulkheads, allowing air to air between compartments and equalize pressure. Open fittings act as direct vents to the atmosphere, so air can escape freely and drop the zone pressure. Since each of these situations creates a leakage path, any one of them can cause loss of zone pressure, making all of the above the correct answer.