Autoclave Vacuum Pumps and “Eco-Friendly” Operations: Look Out for Hidden Costs!
By: Priorclave North America
Category: Lab Design

More labs are taking sustainability more seriously. That’s fantastic! But it also means that more equipment manufacturers are promoting dubious claims to sustainability by hyping the “efficiency” of their “eco-friendly” autoclave features.
As we’ve said before, tweaking an inefficient design so that it wastes less water is not the same as creating an efficient design. Over the past several decades, Priorclave has consistently found that seemingly minor design decisions can have profound effects. Autoclave vacuum pump features are a perfect example:
One small component choice (that you might not even know about) has a profound effect on sustainability.
Why Does an Autoclave Need a Vacuum Pump?
Autoclaves sterilize loads using heat and pressure. The load is placed in a sealed chamber and the chamber is flooded with steam. This drives up the temperature and pressure, destroying pathogens and biological contaminants.
Given that the goal is to increase chamber pressure, and a vacuum pump decreases pressure in a sealed vessel, it’s reasonable to ask why an autoclave needs one at all.
The answer is that some loads tend to harbor pockets of cold air, creating conditions in which pathogens can survive the sterilization cycle. This is especially true of two fairly common load types:
- “porous loads” like textiles, garments, and anything packaged in steam/air-permeable autoclavable wrappings. This category also includes irregular loads full of small airways (e.g., stoppers and tubing), which create baffles that steam has trouble navigating
- “air traps” like red-bagged waste and narrow-mouthed flasks
Autoclaves with a built-in vacuum pump can run a “pre-cycle vacuum stage” prior to the sterilization cycle as part of their program. During a pre-cycle vac stage, the vacuum pump begins to draw a partial vacuum in the chamber. Meanwhile, the chamber is also being flooded with steam. By “pulsing” this vacuum, the pump churns the air and steam in the chamber, forcing steam through porous materials and into every nook and cranny of an irregular load. This eliminates cold pockets, ensuring even steam contact throughout the load.
Tests have found that even a single pre-cycle vacuum pulse will improve sterilization by about 90 percent. Using three pre-cycle vacuum pulses virtually guarantees successful sterilization.
As an added bonus, most autoclaves with a vacuum pump can also offer post-cycle vacuum stages. In this case, the pump runs after completing the sterilization cycle. This clears the chamber of steam before it can condense, leading to drier finished loads.
What Are Your Vacuum Pump Options?
There are three types of vacuum pumps used in autoclaves:
- Venturi ejectors are cheap, powerful, and easy to maintain—they have almost no moving parts, and require no power! But they use dozens to hundreds of gallons of water per autoclave cycle just to create a partial vacuum.
- Diaphragm vacuum pumps are more efficient than ejectors, in terms of water consumption. But they have more moving parts. This drives up cost for the pump itself, as well as maintenance costs. The machine needs to be regularly taken offline for valve checks and diaphragm replacement. Additionally, in autoclave applications, diaphragm pumps generally can only reduce the chamber pressure to about 500–600 mbar, making them less effective when attempting to sterilize tricky loads.
- Liquid ring vacuum pumps are more expensive than either ejectors or diaphragm pumps. They require a larger electrical supply and a piped water supply. But they are designed to be low-maintenance, with few moving parts prone to failure. Even more importantly, they easily create vacuums down to 30–100 mbar—comparable to an ejector—without pouring hundreds of gallons of water down the drain.
Most North American autoclave manufacturers still favor Venturi ejectors. It’s a cheap, effective solution—from a manufacturing standpoint. But saving money during manufacturing can become astoundingly expensive over an autoclave’s decades-long service life.
For years, experts have advised that labs move away from ejectors. In 2013, a team at Stanford noted that “replacing the steam sterilizer’s water ejector with a liquid ring vacuum pump (for vacuum creation) can greatly reduce water consumption … [W]ater used to create a vacuum can be reduced by up to 75 percent with this type of modification. When purchasing a new sterilizer, selecting a model with an electric liquid ring vacuum pump is essential for water efficiency.”
Priorclave Balances Efficiency With Efficacy
At Priorclave North America, we always outfit our vacuum-equipped autoclaves with liquid ring vacuum pumps. This choice plays a major role in the notable water consumption difference between Priorclaves and other brands, without compromising reliability or increasing maintenance issues with our autoclaves. If you need an autoclave with a vacuum, it’s worth checking what type of vacuum pump is installed, and whether a better and more efficient liquid ring pump is an option.
We are proud to support cutting-edge research and work with labs and investigators worldwide. If you have questions about how to get started building an autoclave customized to meet your needs, please feel free to reach out today.