Which type of water MUST be used with the autoclave?

• A. Tap water
• B. Sterile water
• C. Filtered water
• D. Distilled water

Answer: (D)

Steam sterilization relies on pure, consistent steam to kill microorganisms. Water used to generate that steam should be free of minerals and contaminants because dissolved salts and minerals can deposit as scale on heating elements and inside the chamber, impair heat transfer, and potentially affect sterilization effectiveness and equipment longevity.

Distilled water is used because it has most impurities removed. By eliminating minerals, it minimizes mineral buildup and corrosion, helping maintain steam quality and the autoclave’s performance. Tap water contains minerals that can leave deposits; filtered water may still have dissolved salts; sterile water isn’t necessary for the autoclave’s steam generation. So distilled water is the appropriate choice to ensure reliable sterilization.