In an operating, water-cooled, multi-box refrigeration system, both low discharge and high suction pressures are being simultaneously experienced. The probable cause for this condition is which of the following?

Correct Answer: Option C — discharge relief valve leaking back to the suction side

Simultaneously low discharge and high suction pressures indicate internal compressor bypassing, typically caused by a leaking compressor discharge valve, relief valve, or worn piston rings. This allows high-side gas to bleed directly back into the low side, equalizing system pressures and reducing pumping efficiency.