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What Water is Best for My Autoclave?

Is Tap Water Bad for Your Steam Autoclave?

With increasing federal demands and support, many U.S. cities and public water systems are addressing water quality issues in their communities with major infrastructure projects. This is so important; keeping lead out of water mains is essential to public health. It also means folks in towns undertaking those improvements are even more aware of local water quality.

As cities make progress on their Lead Service Line Inventory and Replacement Plans (LSLI/LSLR), we’ve noticed rising concern among organizations with lab facilities. Lead, of course, isn’t the issue (when water is converted to steam, any heavy metal contaminants are left behind in the reservoir). But they want to know more generally: Is tap water bad for our autoclave? Is our tap water bad for our autoclave? Should we be autoclaving with distilled water? Purified water?

For almost everyone who uses a steam autoclave in research, education, industrial, or food & beverage contexts, tap water works fine. In fact, because most of these autoclaves use conductivity to detect water level in their chamber or tank, they will not function properly if run exclusively using distilled or purified water.

But, while tap water is generally the best water source for lab autoclaves, you should be aware of a few key potential issues with any water supply. 

(Note: Priorcalve North American specializes in autoclaves for research, education, and industrial use. What’s fine in research and development isn’t necessarily OK for healthcare: if you are in a medical setting, or anywhere that mandates the use of a medical, dental, or other “FDA-approved” autoclave, our advice is not for you! Check this out instead.)

Challenges of Tap

Tap water often means hard water—water that’s high in minerals. About 85 percent of the United States has hard water. Hard water is safe for cooking and washing. In fact, some studies even suggest some health benefits to drinking hard water. But it’s not great if you’re any appliance or equipment that regularly heats water—and your autoclave is no exception: hard water is hard on an autoclave. Using hard water over the long haul will drive up utility costs and strain the autoclave, increasing maintenance and decreasing lifespan.

Hard water is high in magnesium, salts, organic molecules and minerals, and calcium carbonate, which builds up—especially on appliances and devices that heat water, like autoclaves. Because some of the minerals in hard water are less soluble in hot water, they tend to collect in the hottest part of your water system (e.g., the heating element in your steam autoclave’s reservoir). There, they form white deposits (“scale” or “limescale”). Left unchecked, this creates an insulating layer that reduces energy efficiency. Eventually, if unaddressed, your efficiency will drop by 20 to 30 percent. Scale can also precipitate out of the water as it changes temperature on its way through the autoclave’s plumbing, clogging valves, constricting pipes and reducing water flow.

As a preventative, even if you have relatively soft water, it’s best to regularly scrub down the heating elements and chamber using a plastic scouring pad and a mild descaling agent (CLR is one popular brand available at most hardware stores).

Test your Water, Spare your Autoclave

If you are planning on installing a steam autoclave—or have one already—now is the time to check your water hardness. You can start by reviewing a recent water quality report from your local water utility, which should include water hardness. But your water could pick up additional minerals along its path to your lab, so that might not be enough information. For an absolute answer, your best option is to get a water hardness test kit (available at most hardware stores, or pet supply stores that carry supplies for fancier aquariums). With a test kit, you can directly test the quality of the water immediately before it enters your autoclave.

Generally speaking, water is “soft” when it has below 17 ppm (parts per million) of calcium carbonate, “slightly hard” between 17 and 60 ppm, “moderately hard” above 60 ppm, and “hard” when it exceeds 120 ppm. (These numbers may also be given in “grains per gallon,” abbreviated “gpg.” Anything below 1 gpg is “soft” and anything above 7 gpg is “hard.”) Ideally, your autoclave would like water below 50 ppm (around 3 gpg).

How Do You Solve a Problem like Limescale?

For the majority of lab, education, industrial, or food & bev autoclave users, tap water quality is, at worst, a minor annoyance—and easily addressed.

If you have “hard” water (120 ppm, or more than 7 gpg), you can nip maintenance headaches in the bud with a consumer-grade water softener from any big-box hardware store. In most cases, a standard water softener will pay for itself in the first six months simply by reducing unnecessary service calls and avoiding all the headaches of unexpected downtime.

Have more questions about how to get the most out of your Priorclave autoclave? Check out our website to learn more, join our mailing list to stay connected, or get in touch with any questions.