Read why tap water is bad for a steam sterilizer / autoclave and learn about tactics that maintain peak performance.

The Insidious Threat: Mineral Buildup and its Devastating Consequences

As a laboratory technician, Vivarium manager, healthcare professional, or someone responsible for operating steam sterilizers, your role in maintaining the efficiency and longevity of this crucial equipment is invaluable. Unfortunately, while tap water might seem readily available and convenient for your steam sterilizer, it can harbor hidden dangers compromising its performance and longevity.

What’s more, tap water contains dissolved minerals that transform into a silent enemy – scale during the high-temperature sterilization process. This scale deposits itself within the intricate network of your sterilizer’s steam generator, pipes, and valves. What might seem like a harmless buildup, hindering heat transfer, acts like a physical barrier.

In sum, this process reduces your sterilizer’s overall efficiency, forcing it to work harder to achieve the necessary sterilization temperatures.

A Buildup of Cascading Problems

Over extended periods, this relentless accumulation can lead to a cascade of problems like:

Malfunctions and Pressure Inconsistencies: Scale accumulates within the system and can obstruct water and steam flow, leading to malfunctions and pressure inconsistencies.

These inconsistencies can compromise the effectiveness of the sterilization process, potentially putting the safety and sterility of your equipment and materials, and ultimately, the health and safety of your patients or research subjects, at risk.

Shortened Lifespan for Your Critical Equipment: The constant battle against scale takes a toll on your sterilizer. The strain on the heating elements and increased pressure fluctuations can accelerate wear and tear, leading to premature equipment failure.

This results in costly repairs, downtime, and potential disruptions to your critical workflow.

Beyond Physical Barriers: How Scale Disrupts the Delicate Balance of Your Sterilizer

A sterilizer’s delicate water-level sensor tubes are particularly vulnerable to scale buildup. These tubes play a crucial role in maintaining the proper water level within the steam generator. When scale clogs these tubes, the tubes malfunction and provide inaccurate readings.

How to spot a scale problem

  • Is the sterilizer overheating or insufficient steam generation? Inaccurate water level readings can lead to situations where the sterilizer believes there’s more water than reality. This reaction causes the system to overheat to maintain pressure, potentially damaging internal components. On the other hand, if the sensor underestimates the water level, it could lead to insufficient steam generation, compromising the sterilization process’s effectiveness.
  • Are your water levels inconsistent? Pay close attention to the water level readings displayed on your sterilizer. If these readings fluctuate significantly during a sterilization cycle, it could indicate scale buildup within the sensor tubes.
  • Does the unit shut down?  Is the pressure fluctuating? Malfunctioning water level sensors due to scale causes a sterilizer to get inaccurate readings. A malfunction will shut the system down to prevent overheating or continue operating with insufficient water, leading to pressure inconsistencies.
  • Is there a visible scale buildup? If you can safely access the water-level sensor tubes (consult your sterilizer’s manual for proper procedure), check for any visible signs of scale accumulation within the tubes. Scale accumulation strongly indicates that scale might affect the sensor’s readings.
  • Can you tell that the unit isn’t running right? If you suspect your water level sensors are malfunctioning, it’s crucial to prioritize the safety and effectiveness of your sterilization process. Consider postponing sterilization cycles until you can address the potential sensor issue and ensure the sterilizer functions correctly.
  • The result: In worst-case scenarios, malfunctioning sensors due to scale buildup can cause heater meltdowns. These meltdowns result in costly repairs and downtime and create a safety hazard.

Water Hardness: Know Your Enemy

Buildup of scale in from a sterilizer autoclave boiler PRIMUS Spire Integrated Solutions

The mineral content of tap water varies greatly depending on location. If you suspect your tap water might be “hard” (meaning it contains high levels of dissolved minerals), it’s crucial to act.

If tap water’s mineral content exceeds 5 grains per gallon (85 mg/L), consider water treatment solutions like demineralization or reverse osmosis. These processes effectively reduce mineral content, minimizing the risk of scale buildup in your sterilizer.

Go to the city to check your municipal water quality report. Although water quality reports are based on human consumption, perhaps these findings can offer some insight into the mineral content of your tap water at your facility.

Did you know that PRIMUS can conduct an independent water quality test for your tap water?

An independent water quality test for tap water is recommended to ensure optimal sterilizer performance. This test will provide an accurate picture of the mineral composition and allow you to tailor your water treatment strategy accordingly.

PRIMUS Sterilizer, Spire Integrated Solutions

Deionized Water: A Double-Edged Sword

Did you know that deionized water, completely stripped of its minerals, is a perfect storm solution for a sterilizer / autoclave? However, deionized water lacks electrical conductivity, essential for adequately functioning water-level sensors in standard (carbon steel) steam generators.

Potential risks of using deionized water in a steam sterilizer

Here are potential risks and consequences of using deionized water in a steam sterilizer with non-stainless steel components:

  • Sensors malfunction: Deionized water lacks electrical conductivity. Standard (carbon steel) steam sterilizers rely on water level sensors based on electrical conductivity. Deionized water, with no ions and minerals, cannot conduct electricity efficiently, leading to wrong readings or sensor malfunctions.
  • Disrupted sterilization cycles: If the water level sensor malfunctions due to deionized water, it can disrupt the entire sterilization cycle. 
  • Overheating: If the sensor cannot read the water level, the system might believe it has more water than it does. Sensors that don’t work cause the sterilizer to over heat to maintain pressure, potentially damaging internal components.

Other risks

  • Insufficient steam generation: On the other hand, if the sensor cannot read the water level, it could lead to not enough steam generation, compromising the effectiveness of the sterilization process.
  • Corrosion of non-stainless steel components: Deionized water’s aggressive nature: Deionized water, lacking minerals, is more likely to attract ions from other materials it encounters. Corrosion causes a leaching effect on non-stainless steel components within the sterilizer. 
  • Pitting and leaks: Deionized water can gradually erode the non-stainless steel components, causing them to develop pits and leaks. Pitting compromises the sterilizer’s integrity and potentially poses safety hazards.
  • Weakening of components: The continuous leaching of ions can weaken the non-stainless steel components over time, making them more susceptible to stress and potential failure.
  • Disruptions in the sterilization process: Sensor malfunctions can compromise the accuracy and effectiveness of the sterilization cycle.
  • Damage to the autoclave: Continuous exposure to deionized water will cause the autoclave to corrode and weaken components. When this happens, it is sure to lead to costly repairs and/or autoclave failure.

By understanding the hidden dangers of tap water and taking proactive steps like water treatment and testing, you can ensure the smooth operation and longevity of your steam sterilizer.

A Healthy Autoclave Equals an Efficient Sterilization Process

Investing in proper water management practices protects your equipment and ensures the consistent delivery of safe and sterile results, which is crucial for any laboratory, vivarium, or healthcare setting.  Spire Integrated Solutions is here to help with Life Science or Healthcare Steam Sterilizers.

Questions?  Need to talk?

There is no obligation to talk to us about how we can help with a sterilizer water situation.

Talk to Dave Schall, our PRIMUS sterilizer expert, to assist you anytime at 877.679.7800 extension 1212 or email at

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