When performing a hydrostatic test on a low pressure evaporator to determine the source of suspected air leaks you should use __________.

Correct Answer: Option A — fresh water at or above the ambient temperature

Hydrostatic testing of low-pressure evaporators requires fresh water at ambient temperature to prevent thermal shock or damage to internal components. This method allows for the safe identification of vacuum leaks without the risks associated with pneumatic testing or the introduction of contaminants into the distilling system.