Last Updated on October 27, 2023


When it comes to using an autoclave, one question that often arises is, “What type of water should I use?” The answer to this question largely depends on the type of autoclave you have. While some autoclaves are connected to the house water or steam supply, giving you limited choices, top-loading autoclaves provide more flexibility.

In this article, we will explore the importance of water selection for autoclaves, specifically focusing on top-loading models. By understanding the significance of water choice and following the recommended guidelines, you can ensure the longevity of your autoclave, efficient sterilization, and a safer laboratory environment.

The Power of Top-Loading Autoclaves

Top-loading autoclaves offer a convenient and independent sterilization solution. Unlike autoclaves connected to water lines or steam supplies, top-loading models require a simple installation, occupy less space, and allow more room for additional equipment. However, one might wonder how these autoclaves generate saturated steam and create optimal conditions for sterilization without an external water or steam source.


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The Secret Lies in Water and the Heating Element

Top-loading autoclaves, such as the SX-Series Autoclave, utilize a powerful heating element located in the base of the main chamber. To activate the autoclave, all you need to do is add water to the top-loading lid, ensuring the heating element is fully submerged. Once the power plug is connected to an appropriate electrical outlet, the installation process is complete, and you’re ready to go.

Understanding Water for Autoclaving

To better understand water selection for autoclaving, let’s explore how water sensors work, tips for choosing the right water, and the rationale behind these recommendations.

Water Level Sensor for Safety

At TOMY, safety is a paramount concern, and thus, each of our autoclaves is equipped with a water level sensor. This sensor plays a crucial role in ensuring the heating element remains submerged. By detecting the ionic content of the water in the system, the sensor prevents the autoclave from operating if the water level is too low or if no ions are detected. Consequently, using pure deionized (DI) water is not advisable since it lacks the necessary ions to activate the sensor, rendering the autoclave inoperable.

The Perils of Mineral Buildup

When considering the type of water to use in autoclaves, preventing mineral buildup is a primary concern. Neglecting this issue can lead to adverse effects on your autoclave and its components. Tap water, although it activates the water level sensor due to its higher ion content, poses a significant drawback. The high mineral content in tap water leads to the accumulation of limescale within the sterilizing chamber, which can be challenging to remove or clean. The severity of this phenomenon varies depending on the location, with some areas experiencing harder tap water than others. For instance, tap water in Southern California is several times harder than that in the Midwest or Northeast of the United States, resulting in faster limescale buildup.

DI Water: A Solution to Limit Mineral Buildup and Prolong Autoclave Life

To strike a balance and mitigate the issues associated with mineral buildup, we recommend using a combination of DI water and tap water. This approach ensures the safe operation of TOMY SX-Series Autoclave and facilitates easier cleaning of the sterilizing chamber. During the autoclave setup, it is advised to add 3-3.5 liters of DI water to the chamber, sufficiently covering the heating element and base plate by at least 5 cm. Additionally, supplement this with a small amount of ion-rich tap water (50 mL for the SX-500 and 100 mL for the SX-700) to enable the water level sensor to function properly while minimizing limescale buildup.

In Summary: Water is Key to Autoclave Performance and Longevity

By following these simple guidelines when adding water to your autoclave, you can ensure its longevity, maintain optimal performance, and create a safe environment for you and your lab members. The combination of DI water and tap water strikes a balance between activating the water level sensor and limiting mineral buildup. This approach allows for efficient sterilization while minimizing the challenges associated with limescale accumulation. Should you have any further questions or inquiries, please do not hesitate to reach out to our dedicated team. We are always delighted to assist you.

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