Recommended water for ultrasonic diffusers

Selecting the right type of water for an ultrasonic diffuser is crucial to the device's efficient operation and durability. Water can contain various minerals and impurities that affect mist production and the rate of sediment buildup inside the diffuser. Below, we discuss the three most commonly considered options— distilled water , filtered water , and tap water —along with their advantages and disadvantages in terms of diffuser operation and lifespan.

Distilled (demineralized) water

• Advantages: Distilled water is almost completely free of minerals and impurities. Therefore, it leaves no residue or "white dust" during evaporation. Using distilled water prevents scale buildup on the ultrasonic element (transducer), protecting the device's internal components and extending its lifespan. The mist from this water is pure and free of mineral particles, which means safer air for users (important for allergy sufferers and those with sensitive respiratory tracts). Because distilled water doesn't leave a residue, you can clean your diffuser less often – with regular use, the device will require a thorough cleaning much less often than with tap water. .
• Disadvantages: Paradoxically, not all diffuser models are compatible with distilled water . Some devices rely on water mineralization for proper sensor operation or effective mist production. Very pure, demineralized water may lack the ions needed for level sensors to detect the presence of water or for optimal liquid atomization. In practice, it has been observed that some diffusers and ultrasonic humidifiers do not produce mist using pure distilled water unless a small amount of tap water containing dissolved minerals is added. Manufacturers also warn against using only distilled water in certain models – for example, the Serene House Ori diffuser manual clearly states that removing minerals (as in distilled or reverse osmosis water) can negatively impact the diffuser's performance , preventing proper mist production. Furthermore, distilled water may be less readily available and generates additional costs, and its use—despite its benefits for device cleanliness—may not be recommended if the manufacturer specifically recommends using a different type of water.

Filtered water (e.g. filtered with a jug or partially demineralized)

• Advantages: Filtered water is a middle ground between distilled and tap water. Filters (carbon, pitcher, etc.) remove some impurities and reduce water hardness, reducing the amount of minerals responsible for sediment . As a result, using filtered water reduces scale buildup on diffuser components compared to regular tap water. At the same time, such water retains a certain minimum amount of mineral ions , which can be beneficial for diffusers that require water conductivity to operate efficiently. This water is often readily available (e.g., obtained from a home filter) and is cheaper than distilled water, while still being device-friendly. Many sources recommend filtered or boiled and cooled water as a good choice, reducing the risk of mineral deposits without causing problems with sensors or mist production.
• Disadvantages: Keep in mind that the degree of mineral reduction depends on the filter used – filtered water is not completely free of mineral salts . Some residue (e.g., calcium carbonate) may still build up over time, especially with heavy use. While the deposit will be less than with tap water, regular cleaning is still necessary to maintain optimal performance. If we use reverse osmosis (RO) filters or other filters that practically demineralize water, such water becomes similar to distilled water – and therefore can cause similar problems with some diffusers (no mist, inactive sensors). For example, the manufacturer Serene House notes that reverse osmosis water contains so few minerals that the diffuser will not be able to properly disperse the mist and achieve the desired results. In summary, while filtered water is safer for your diffuser than hard tap water , it still requires some maintenance.

Tap water (tap water)

• Advantages: Tap water is the most accessible and convenient choice – it doesn't require purchasing or special preparation. Some manufacturers even recommend using regular tap water (unless it's extremely hard), as it contains natural minerals that ensure proper operation of the diffuser . Tap water, especially in regions with soft water, can be used without serious side effects, provided the device is regularly cleaned and maintained. If the diffuser is used occasionally (e.g., a few times a week for short periods), small amounts of sediment from tap water are unlikely to cause immediate performance degradation. It's also worth noting that tap water contains chlorine and other substances that limit the growth of microorganisms, which can be an added advantage as long as the water doesn't sit in the tank for long.
• Cons: The main problem with tap water is its high dissolved mineral content , especially in areas with hard water (rich in calcium and magnesium). While the ultrasonic diffuser is in operation, the water turns into a cool mist, but the minerals don't evaporate —they settle inside the device or float in the air as fine dust, which then falls onto furniture. Over time, a layer of scale builds up on the ultrasonic transducer and tank walls, reducing the diffuser's efficiency (making it harder to produce mist) and potentially causing failure if the device is not cleaned regularly. Studies show that continued use of hard water can shorten the life of your diffuser by up to half due to accelerated wear of the deposited components. Furthermore, tap water mist contains mineral particles that can degrade indoor air quality (so-called white dust can be inhaled or settle on electronics and surfaces). Using tap water therefore requires increased maintenance – emptying the tank after each use, rinsing, and frequently descaling the ultrasonic element to prevent scale buildup.

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Why shouldn't all diffusers run on distilled water?

From a durability perspective, distilled water seems ideal (zero sediment), but as mentioned, not every ultrasonic diffuser will function properly with completely mineral-free water . This is due to the design and operation of such devices:

• Water Level Sensors: Many diffusers and humidifiers have a safety feature that shuts off the device when the reservoir is empty. A simple detection method often relies on the electrical conductivity of water – two contacts are immersed in the liquid, and a current flow indicates the presence of water. Distilled water is a poor conductor (lacking ions), so sensors may not see it. As a result, a diffuser equipped with this mechanism may falsely indicate an empty reservoir or fail to turn on at all, even though it is filled with distilled water.
• Ultrasonic water dispersion process: Although the mist is generated mechanically (piezoelectric vibrations disperse water into micro-droplets), user experience shows that completely pure water sometimes creates a mist less efficiently or even invisible . One hypothesis suggests that small impurities and minerals may act as condensation centers for the droplets, facilitating the formation of a visible mist. Without these condensation "nuclei," the vapor can be ultrafine and less noticeable. This can give the user the impression that the diffuser is "not working" with distilled water, when in fact it is, but the mist is less visible or dissipates quickly.
• Manufacturer Recommendations: Many manufacturers highlight the water type in their user manuals. For example, some models recommend using only distilled or demineralized water to protect the device from limescale (e.g., Airome diffusers). or some advanced humidifiers). However, other manufacturers strongly advise against using distilled water , citing technical limitations. In the previously cited instructions for the Serene House Ori diffuser, the manufacturer recommends using tap water, soft water, or mineral water , but clearly states: "It is important not to use distilled water, as it has removed minerals that affect the performance of diffusers." Reverse osmosis water is similarly discouraged for the same reason. Even popular aroma diffuser models (e.g., Tisserand Aroma Spa) include a "Do not use distilled water" warning in their manuals. .

In summary: before using a new ultrasonic device, it's worth checking the instructions in its documentation. If the manufacturer recommends a specific water type, it's important to adhere to this recommendation for optimal performance and device durability.