What kind of liquid coolant should I fill into my XMG OASIS?

Summary

For reliable long-term operation of the XMG OASIS, we recommend using only high-quality, additive-free distilled water with certified purity. Of particular importance are low electrical conductivity, low concentrations of dissolved minerals and other contaminants - and to replace the distilled water on a regular basis.

Our current product recommendation is SANISMART AQUA DEST, for which the manufacturer specifies an electrical conductivity of less than 0.9 µS/cm at the time of bottling.

Listings:

• SANISMART AQUA DEST on bestware
• SANISMART AQUA DEST at the manufacturer's page (in Germany)

A 1-litre bottle is included with every new XMG OASIS. Links to similar products across a number of European countries are listed in this paragraph:

• Where can I buy distilled water?

We recommend replacing as much of the coolant as possible every three months to flush out accumulated contaminants and keep the water as pure as possible.

What makes the XMG OASIS different from conventional desktop liquid cooling systems?

There are several approaches to PC liquid cooling. They all differ in their design, maintenance requirements and intended use.

All-in-one (AiO) liquid coolers are filled with a specially formulated coolant at the factory and permanently sealed.

These products are generally designed so that end users neither need to nor are expected to replace or refill the coolant during the intended service life. Opening them without damage is often not even possible due to the way these products are constructed. AiO coolers are aimed at a broad customer base and are intended to operate with zero maintenance.

Custom liquid cooling loops take a different approach. They consist of individually selected components and can be opened, modified, cleaned and refilled as required. However, this ability to perform maintenance does not mean that such a loop is regularly opened during normal operation. Quite the opposite: once assembled, a custom loop typically remains closed for many months or even years. The connections carrying the coolant are not disconnected during everyday use.

Custom loops are primarily aimed at technically experienced enthusiasts. Users often plan, select and assemble the components themselves. This includes choosing suitable materials and coolants, checking all connections for leaks and performing long-term maintenance. With self-built systems, the user is responsible for correct integration and assembly. Troubleshooting or repairing leaks also requires appropriate technical knowledge. Although pre-assembled custom loops are available, this approach generally involves a greater degree of personal responsibility than a conventional AiO cooler.

The XMG OASIS combines certain characteristics of both approaches, but differs in one crucial respect: it was specifically developed for mobile use with a laptop.

While the components of a desktop liquid cooling system normally remain permanently connected, the XMG OASIS can be disconnected from the laptop at any time. Whenever the laptop is taken elsewhere, the connection to the external cooling unit must be detached. It is then reconnected the next time the laptop is used at a desk.

These regular disconnection procedures are explicitly part of the intended use. For this reason, the XMG OASIS features dedicated quick-release connectors and a user-accessible reservoir. As a result, it is inevitable that the water connectors, and occasionally the coolant itself, come into contact with ambient air or other external influences. Under these conditions, a permanently hermetically sealed cooling loop is not possible.

At the same time, the XMG OASIS is not a custom loop kit for liquid cooling enthusiasts, but a largely pre-assembled consumer product. It is designed to make the benefits of external liquid cooling accessible to a broader customer base without requiring specialist knowledge of fittings or coolant chemistry.

Of course, the XMG OASIS is not entirely maintenance-free. Regular cleaning of the connectors, topping up the water and completely replacing the coolant every three months are all part of its intended operation.

This combination of portability, a cooling loop designed for frequent disconnections and straightforward handling is the main difference in comparison to conventional desktop liquid cooling systems.

These characteristics create different requirements for material selection, coolant and maintenance compared to desktop PCs. Rather than relying on a chemically complex coolant formulation intended for a permanently closed loop, we use high-quality, additive-free water and recommend replacing it regularly.

The following sections explain the technical reasoning behind this decision.

Details about the recommended coolant

Where can I buy distilled water?

Distilled or demineralised water is available from pharmacies, drugstores, hardware stores, medical supply retailers and online shops. However, the products on offer can differ considerably in their purification methods, purity and certification. A generic label such as "distilled water" or "demineralised water" is not sufficient proof of quality on its own.

When choosing a product, pay particular attention to the following criteria:

• Clean, undamaged packaging, preferably with the original factory seal intact.
• Electrical conductivity as low as possible (measured in µS/cm).
• Low concentrations of chlorides, minerals and other dissolved substances, without chemical additives. In short, documented purity, for example through compliance with appropriate standards.

We have collected a number of suitable shop listings from across Europe:

If you are looking for similar products in your country or region, the standards listed in the table below provide a useful, verifiable reference when assessing water quality. A manufacturer's specification for electrical conductivity is also helpful, ideally 1 µS/cm or less.

What do the different terms and standards mean?

Distilled water is used in various industries, including medicine, laboratories and batteries. Accordingly, numerous standards exist that define water quality requirements.

Apart from these standards, various common terms for purified water are also used in retail:

Ultimately, the term "distilled water" as used in retail does not necessarily indicate which purification process was actually applied. Our recommendation therefore depends not only on the production method, but also on the documented purity of the finished product.

What is electrical conductivity?

Electrical conductivity describes how well a material can conduct electric current.

In water, conductivity depends largely on the concentration and mobility of dissolved ions. Examples include sodium, calcium, chloride and sulphate ions.

The more of these electrically charged particles are present, the better the water can conduct electricity.

Conductivity is typically expressed in microsiemens per centimetre, abbreviated µS/cm.

For comparison:

• Theoretically ideal ultrapure water has a conductivity of approximately 0.055 µS/cm at 25 °C.
• Particularly pure technical-grade water often has a conductivity in the region of 1 µS/cm.
• Ordinary German tap water can reach several hundred to more than 1,000 µS/cm.

Low electrical conductivity is desirable for the XMG OASIS for two reasons.

• First, it indicates that the water contains only small amounts of dissolved, electrically conductive substances.
• Second, low conductivity increases the electrical resistance of the water. This can substantially limit potential electrochemical currents between different metal surfaces.

The second aspect is particularly relevant to galvanic corrosion, which we explain further below.

Comparison with our previous recommendation

Since the launch of the XMG OASIS, we have included a bottle of distilled water with every cooling unit.

For many years, we used a product from the brand Robbyrob. Its label referenced several standards, including DIN 13060, DIN 43530 and EN 285. In 2026, we switched the supplied product to SANISMART AQUA DEST.

The reason for this change was the packaging, specifically the material properties of the bottle itself. When shipping individual bottles of water together with PC hardware, a sufficiently robust plastic bottle is particularly important. Thin-walled containers can be damaged and leak under unfavourable shipping conditions.

The SANISMART AQUA DEST bottle has a more robust construction. We also use a shipping carton specifically matched to the bottle to reduce the risk of transport damage.

In terms of water quality, we consider both the previous Robbyrob product and the new SANISMART AQUA DEST highly suitable. Robbyrob was labelled with a larger number of standards, whereas SANISMART additionally provides a specific, particularly low conductivity value.

Why does the SANISMART bottle state that the water is unsuitable for eye drops or infusions?

This warning refers to medical applications and does not contradict our recommendation for the XMG OASIS. Infusions, injections and certain ophthalmic applications are subject to additional pharmaceutical quality requirements.

Depending on the application, these include requirements concerning sterility, microbial contamination, endotoxins and the corresponding manufacturing and testing procedures. Very low electrical conductivity is not proof of pharmaceutical sterility.

The XMG OASIS should also use water that is as clean as possible. However, its requirements differ from those of a liquid intended to be introduced directly into the human body. The warning on the SANISMART bottle therefore does not indicate any disadvantage for use in our liquid cooling system.

Is UV-treated water better?

UV radiation can inactivate microorganisms and is therefore used in various water treatment processes. However, UV treatment does not remove dissolved minerals and is no substitute for low electrical conductivity. UV-treated water is therefore not automatically better than a comparably pure product without documented UV treatment.

Can I use tap water if I don't have distilled water available?

No. Not even for testing.

Tap water contains significantly more dissolved minerals and salts than the distilled water we recommend. This considerably increases electrical conductivity. In addition, limescale, chlorides and other constituents can promote deposits or corrosion processes.

Once unsuitable water has been added, residual amounts or deposits may remain in the loop even after the liquid has been drained. For this reason, tap water should not be used even for brief functionality tests.

What should I do to keep my XMG OASIS in optimal condition over the long term?

Replace the coolant every three months.

We recommend replacing the coolant as completely as possible every three months. The used coolant should be removed from the XMG OASIS reservoir. The loop should then be refilled with fresh distilled water.

This maintenance interval may seem conservative. We deliberately chose it to limit the accumulation of contaminants and minimise the long-term risk of corrosion. Each water change removes dissolved and suspended contaminants before they can accumulate in the loop over extended periods.

We also recommend the following:

• Switch off the XMG OASIS before disconnecting the tubes.
• After disconnection, remove any remaining water droplets using the supplied microfibre cloth.
• Regularly inspect the water connectors on the laptop and tubes for dust and other contaminants.
• Clean the connectors and surrounding surfaces with the supplied brush and microfibre cloth when necessary.
• Make sure no foreign objects enter the exposed water connectors.
• Whenever possible, use distilled water directly from its original bottle.

Why isn't simply topping up the water sufficient?

The chemical composition of the water can change during operation.

The water absorbs substances from the surfaces of the cooling loop. Contaminants can also enter the coolant through contact with air, connecting and disconnecting the tubes, and tiny manufacturing residues.

If fresh water is merely added to top up the reservoir, most of the substances already dissolved in the coolant remain in the loop.

By contrast, completely replacing the water in the reservoir significantly reduces their concentration, even though it is not possible to remove every last drop of water from the entire cooling loop.

Particularly during the first few months of operation, water changes can also help gradually remove manufacturing residues. However, some materials continue to release small amounts of substances into the water even after this initial period. For these reasons, regular water changes remain beneficial even for a system that has already been in use for a long time.

Can I skip water changes if I rarely use the XMG OASIS?

Even when the XMG OASIS is switched off and the water is not actively circulating, the coolant remains in contact with the surfaces of the cooling loop. Chemical reactions, the dissolution of substances and changes in water chemistry do not necessarily require the pump to be running.

Some processes may proceed more slowly at lower temperatures and without water flow. However, this does not provide a basis for establishing a generally applicable, longer maintenance interval. We therefore recommend continuing to replace the water every three months even with infrequent use, as long as the system remains filled. Alternatively, the system can be stored with the cooling loop drained as completely as possible.

What should I do if the coolant becomes cloudy or visible deposits appear?

Any clearly visible change in the coolant should not be ignored. Cloudiness, flakes, unusual discolouration or visible deposits may indicate contamination or undesirable reactions within the cooling loop.

In such cases, we recommend discontinuing use of the XMG OASIS and contacting XMG Support, particularly if these symptoms first appear after the system has already been in use for several years.

We also explicitly advise against adding cleaning agents, descalers or chemical additives in such situations.

How does water quality change over time, and why does it matter?

Factors affecting water purity

Even when a cooling loop is filled with particularly pure water, that water does not remain in its original condition indefinitely.

There are several reasons for this.

• Tiny residues can be introduced during the manufacturing and assembly of components that carry water. These may include particles, machining residues or substances left over from production processes. Repeated complete water changes should gradually reduce these residues over time.
• Even clean plastics and metals can release small amounts of substances into the water over extended periods. The resulting concentrations depend on factors including temperature, material properties and contact time.
• Through contact with ambient air, water absorbs oxygen and carbon dioxide (CO₂), changing its chemical equilibrium.
• When the cooling loop is opened, tiny dust particles or other foreign substances at the connectors may come into contact with the coolant.

For these reasons, we recommend replacing the water regularly, approximately every three months.

How quickly can electrical conductivity increase?

The coolant manufacturer Dynalene has published an investigation into this subject. In an experimental liquid cooling loop, highly purified water with an initial conductivity of 1.72 µS/cm was used. Before the experiment, the loop was flushed several times with highly purified water to remove existing contaminants.

Dynalene then operated the loop under the following conditions:

Within less than six days, electrical conductivity increased to approximately seven times its initial value. However, this was an experimental setup operated continuously under high thermal load, with constant water circulation and no idle periods or intermittent shutdowns. The test conditions therefore cannot be directly applied to normal XMG OASIS operation.

Nevertheless, the investigation demonstrated that even a cooling loop that has already been flushed can continue releasing dissolved substances into the water.

How does the electrical conductivity of tap water compare?

Ordinary tap water has a much higher electrical conductivity than high-quality distilled water. Depending on water quality, the difference can range from several hundred to several thousand times.

This is due to the minerals and salts present in drinking water, including calcium, magnesium, sodium, chlorides and sulphates. These substances are not inherently problematic for drinking water quality, but they increase electrical conductivity.

The actual value depends on the regional water supply. In Germany, for example, values between 500 and 1,000 µS/cm are not uncommon.

The following table compares various values with our recommended SANISMART AQUA DEST:

What do these values mean for the possibility of galvanic corrosion?

Electrical conductivity and electrical resistance are inversely proportional for a given geometry. Lower conductivity therefore increases the electrical resistance of the coolant. Compared with tap water, the difference spans several orders of magnitude.

For example, if a liquid has 1,000 times the electrical conductivity, the same column of water will have only one-thousandth of the electrical resistance.

Lower electrical resistance makes it easier for electric charge to move through the liquid, potentially promoting electrochemical corrosion processes.

In addition, tap water contains significantly higher concentrations of dissolved minerals, which can cause deposits. Certain constituents, such as chlorides, can also promote localised corrosion.

Regularly replacing the coolant with distilled water therefore creates favourable conditions for reliable long-term operation of the XMG OASIS.

Should I be concerned about galvanic corrosion?

Understanding galvanic corrosion

Galvanic corrosion is an electrochemical process that can occur when different metals are coupled together. Different metals have different electrochemical potentials. Under suitable conditions, this can generate an electric current that accelerates corrosion of the less noble metal.

A conventional galvanic couple requires:

1. Two different metals or metal surfaces with different electrochemical potentials.
2. A shared electrolyte, such as water containing dissolved ions.
3. An electrically conductive return path between the metal surfaces.

It is important to distinguish between two types of charge transport.

The electrochemical process requires both types of charge transport.

What materials are used for the water-carrying tube inside the laptop?

The water-carrying tubes in our XMG laptops are always made from a single piece of metal. Depending on the model, either copper or aluminium is used.

Aluminium was chosen for certain models to reduce weight. The impact on cooling performance is minimal.

In all models, the tube is connected more or less directly to the heatpipes of the conventional air cooling system along its entire length:

• In most models, it is soldered onto the heatpipes from above.
• Starting with the XMG NEO 16 (E24), it is integrated into the copper block as an internal channel.

Example diagrams:

Why is copper generally used inside the laptop?

Copper has high thermal conductivity. This is particularly beneficial in compact cooling systems, where there is very limited space to absorb and transfer waste heat from the processor, graphics card and other components. Copper is also mechanically robust and well suited to thin-walled cooling structures, such as the cooling fins at the laptop's air exhaust vents, which are connected to the copper heatpipes of the air cooling system.

Why is the XMG OASIS radiator made from aluminium?

Different design considerations apply to the external radiator. Inside the laptop, every millimetre of space and every gram of weight matters. The external cooling unit, by contrast, provides considerably more room for a large heat exchanger.

An aluminium radiator offers a favourable balance of thermal performance, size, weight and cost. A radiator made entirely from copper would be significantly heavier and more expensive. Since the cooling performance of the overall system is also limited by water flow rate (including the diameter of the water channel inside the laptop and pump noise) and heat transfer (including the PTM thermal interface material and the internal surface of the water channel), switching to copper would not provide a meaningful thermal advantage for the XMG OASIS.

Using aluminium is therefore a deliberate technical and economic decision.

How do the different materials interact?

As shown in the table above, there are two different designs. Both have different technical characteristics. Using particularly pure water and regularly replacing the coolant makes sense for both variants.

Laptop models with a copper water channel

Copper is the more noble metal compared to aluminium because it has a lower tendency to release electrons and dissolve into the coolant as metal ions.

In a galvanic couple between these two materials, aluminium typically acts as the anode, while copper acts as the cathode and is therefore generally protected against galvanic corrosion.

In this arrangement, the more noble metal is located inside the laptop, while the potentially more vulnerable aluminium radiator is part of the external cooling unit, which is easier to replace or repair.

Laptop models with an aluminium water channel

Three OASIS-compatible laptop models have an aluminium water-carrying tube inside the laptop:

• XMG NEO 16 (E23)
• XMG NEO 17 (E23)
• XMG NEO 17 (E24)

Since the external XMG OASIS radiator is also made from aluminium, these models do not have a galvanic material pairing between copper and aluminium across the two heat exchangers. Although the copper heatpipes of the conventional air cooling system remain thermally connected to the aluminium tube, they do not come into contact with the coolant.

Using aluminium on both sides is initially advantageous in terms of galvanic corrosion. When exposed to water and oxygen, aluminium forms a thin, protective oxide layer. Under suitable conditions, this process, known as passivation, prevents the underlying metal from being continuously attacked.

However, under unfavourable conditions, this protective layer can suffer localised damage. Elevated chloride concentrations, unfavourable pH values and deposits are particularly problematic.

Our recommendation therefore remains the same for this material configuration: use high-quality, additive-free distilled water with the lowest possible electrical conductivity and replace the coolant regularly. This reduces both potential galvanic corrosion processes and the concentration of contaminants that could attack aluminium independently of contact with other metals.

What about the internal geometry of the water channel?

One important characteristic of our laptop liquid cooling system is the comparatively simple geometry of its internal water channel. In conventional PC water blocks, coolant is often directed through very fine microchannels or between closely spaced metal fins.

For comparison: typical desktop liquid cooling (CPU)

Image source: Corsair Hydro Series H80

The photo shows the inside of the copper cold plate. Once the cooling block is assembled, this finned surface comes into contact with the coolant. This type of construction provides a large surface area for heat transfer but can be more sensitive to deposits or particles.

Water channel inside the XMG NEO

In the corresponding XMG laptops, we instead use a continuous water channel without such microstructures. The channel follows a curved path through the copper thermal module and does not contain similarly complex microfins.

This simple channel geometry offers several advantages:

• Lower sensitivity to small amounts of particles moving through the coolant.
• Fewer potential bottlenecks where deposits could accumulate.
• Easier coolant replacement and better flushing characteristics.
• Fewer abrupt changes in flow direction and potential locations for localised flow disturbances.

For the laptop's internal water channel, this simple geometry therefore significantly reduces the risk of corrosion-related flow restrictions compared with a finely structured microchannel water block.

How does the length of the water tubes between the XMG OASIS and the laptop affect corrosion?

A long, narrow column of water has significantly higher electrical resistance than a short, wide column containing the same liquid. For comparison, a water column with a diameter of 3 mm has approximately 78% higher electrical resistance than one with a diameter of 4 mm. This relationship follows the square of the diameter.

Higher electrical resistance limits potential galvanic currents through this water path, thereby reducing the risk of galvanic corrosion.

The XMG OASIS and the laptop are connected by two relatively narrow plastic tubes, each approximately 65 cm long. These long water paths are an important difference compared with cooling systems in which different metal surfaces are positioned directly next to each other.

Together with the use of water with the lowest possible conductivity, the geometry of the water tubes therefore also reduces the potential for galvanic corrosion.

Is damage to the copper thermal module still possible?

Compared with aluminium, copper is on the more favourable side of the electrochemical relationship between these materials. In a corresponding galvanic couple, corrosion of the aluminium would typically be accelerated, while copper would experience a cathodic effect.

However, copper can also corrode independently of galvanic coupling, for example due to unfavourable water chemistry, dissolved oxygen or localised contamination.

Several factors work in favour of our design:

• Using water that is as pure as possible reduces the concentration of potentially problematic dissolved substances.
• Low conductivity increases the resistance of potential ionic current paths.
• Regular water changes limit the accumulation of contaminants.
• The simple geometry of the corresponding water channels reduces sensitivity to deposits and certain flow-related problems.

For these reasons, we consider the risk of corrosion-related damage to the copper thermal module relatively low when the system is used as intended.

Why don't we recommend PC coolants with chemical additives?

Commercial coolants for desktop PCs often contain various chemical additives, including:

• Corrosion inhibitors to protect metal surfaces.
• Biocides or other active substances to prevent microbial growth.
• Glycol or similar substances to modify antifreeze properties and other fluid characteristics.
• Dyes for visual effects.

Such additives are not inherently unsuitable or ineffective. They can serve important purposes in closed cooling loops that have been validated for their use. Many manufacturers of desktop liquid cooling systems therefore deliberately use formulated coolants, particularly when different metals are present in the same cooling loop.

Our decision not to support PC coolants with chemical additives is nevertheless based on several technical and practical considerations.

Material compatibility

Besides metals, the cooling loop also contains various plastics, seals and other components. Not every chemical additive is compatible with every material over the long term. Depending on the formulation, chemical additives may, for example, promote stress cracking, changes in material properties, swelling of seals or undesirable deposits.

We have also continued optimising the materials used throughout the development of the XMG OASIS. In the second hardware revision of the original OASIS, for example, certain tube connectors were changed from PC/ABS to POM (polyoxymethylene).

POM offers greater mechanical robustness and is compatible with a wider range of coolant formulations than the previously used plastic combination. However, this does not automatically mean that all commercial PC coolants are suitable for every component and generation of the XMG OASIS.

Different coolant formulations

A wide variety of coolant formulations are available on the market. Their exact composition is often not fully disclosed to end users. Manufacturers may also change their formulations or suppliers.

It would therefore be impossible to make a reliable blanket statement about the long-term compatibility of all these products.

Additional chemical complexity

Chemical additives can degrade, become depleted or be affected by other substances over time. This introduces additional factors that are not present in the same way when using pure water. We deliberately want to avoid this complexity with the XMG OASIS. Our approach is therefore to use water that is as pure as possible and replace it regularly, rather than relying on the long-term effectiveness of unknown coolant additives.

Health and safety considerations

The potential health risks associated with commercial PC coolants depend on the substances they contain and their concentrations. Not every product is automatically toxic or dangerous after brief skin contact.

The chemical additives in specialised PC liquid cooling fluids may irritate the eyes or mucous membranes and require special precautions. The relevant safety data sheets provide the authoritative information.

The XMG OASIS is sometimes used in living spaces where children or pets may also be present. When disconnecting the tubes, individual water droplets may remain at the connectors. User errors or technical defects can also result in larger coolant leaks.

In these situations, we want to avoid additional chemical hazards wherever possible. From this perspective, additive-free distilled water is the simpler solution.

Why not use coolants intended for cars or heating systems?

Automotive antifreeze and specially treated heating system water are also not approved for use with the XMG OASIS. These fluids were developed for different technical applications, involving very different materials, temperature ranges, flow rates, maintenance intervals and operating conditions.

The same principle therefore applies: we explicitly do not recommend using custom or unsuitable coolant mixtures or other additives.

Isn't particularly pure water especially "aggressive" or "hungry"?

Discussions about distilled or deionised water often include the claim that particularly pure water is inherently aggressive because it tends to absorb as many substances as possible from its surroundings. According to this argument, particularly pure water could even cause more corrosion than ordinary tap water.

This idea is based on a genuine physicochemical phenomenon. However, the general conclusion drawn from it is incorrect. We would like to demonstrate this using several arguments and scientific studies.

What happens when particularly pure water comes into contact with other substances?

Water is a good solvent. It can absorb salts, gases and numerous other substances. Particularly pure water initially contains many of these substances only in very low concentrations. As a result, certain soluble residues or constituents of material surfaces may dissolve into the water until a new chemical equilibrium is established. This process is commonly referred to as leaching.

However, the dissolution of existing substances must not be confused with the actual corrosion of a metal. Corrosion is a chemical or electrochemical process in which the metal itself is attacked. This distinction has also been confirmed by scientific investigations and experiments involving industrial installations.

Study #1: Oak Ridge National Laboratory (ORNL)

In 2010, Oak Ridge National Laboratory (ORNL) conducted an extensive technical assessment of the water chemistry in the cooling systems of the Spallation Neutron Source. The original planning documents had assumed that particularly pure water was more aggressive and that excessively high water purity should therefore be avoided.

The author of the assessment explicitly disagreed with this assumption.

The recommendation was to aim for the highest possible water purity and electrical resistance in order to minimise corrosion.

The assessment also explains that corrosion inhibitors are generally unnecessary in ultrapure-water cooling systems operated under appropriate conditions. Such additives could even cause undesirable side effects (source).

Study #2: International Atomic Energy Agency (IAEA)

In 2003, the International Atomic Energy Agency (IAEA) published an extensive research report examining the long-term corrosion of aluminium in water. The report documents operational experience from research reactors in which aluminium alloys had been immersed in particularly pure water for many years.

With consistent monitoring of water quality and electrical conductivity values typically between 1 and 3 µS/cm, several facilities reported little or no pitting corrosion. Some documented operating histories extend beyond 25 years.

The report attributes the low tendency towards corrosion primarily to the high electrical resistance of the water and the low concentration of corrosion-promoting contaminants such as chlorides (source).

What about the absorption of oxygen and CO₂?

Particularly pure water begins changing its properties as soon as it comes into contact with ambient air. Among other substances, it absorbs carbon dioxide (CO₂), which contributes to the formation of bicarbonate and hydrogen ions in the water. This can change both the pH value and electrical conductivity.

The process begins immediately upon exposure to air. Depending on the volume of water, exposed surface area and degree of mixing, CO₂ absorption may become clearly measurable within seconds or develop over several hours or longer.

However, an important point is that a chemical equilibrium is established at a constant ambient CO₂ concentration. The increase therefore does not continue indefinitely.

Study #3: National Institute of Standards and Technology (NIST)

According to the National Institute of Standards and Technology (NIST), theoretically ideal ultrapure water has an electrical conductivity of approximately 0.055 µS/cm at 25 °C. Once it reaches equilibrium with ordinary ambient air, a typical value of approximately 1.05 µS/cm is observed. Depending on CO₂ concentration, values may also range between 0.8 and 1.2 µS/cm (source).

For comparison, our recommended SANISMART AQUA DEST already has an electrical conductivity of less than 0.9 µS/cm at the time of bottling.

Under normal ambient conditions (regular ventilation is recommended to keep indoor CO₂ levels in check), the contribution to conductivity therefore remains in the region of just 1 µS/cm. Compared with the several hundred µS/cm typical of ordinary tap water, the CO₂-related contribution remains negligible. The absorption of CO₂ is therefore also not an argument against using particularly pure water.

Conclusion: Why we recommend distilled water exclusively

The XMG OASIS combines powerful external liquid cooling with a compact cooling system inside the laptop. The materials and design requirements differ considerably in some respects from those of a conventional desktop liquid cooling system. We have therefore deliberately adopted a conservative approach.

• Water that is as pure as possible.

By using high-quality distilled water with low electrical conductivity, we reduce the concentration of dissolved substances and increase the resistance of potential electrochemical current paths.

• Regular replacement.

By replacing the water every three months as recommended, we limit the long-term accumulation of contaminants and reduce our dependence on the coolant remaining chemically stable over extended periods.

• No chemical additives.

We deliberately avoid additional corrosion inhibitors, biocides, antifreeze agents and dyes. This prevents additional uncertainties regarding material compatibility, long-term behaviour and handling.

• A design intended for long-term reliability.

In the corresponding laptop models, the water channel has a simple design without sensitive microchannel structures. The combination of different metals is accounted for through water quality, system design and the prescribed maintenance measures.

None of these measures alone can completely eliminate every conceivable corrosion or ageing process. Together, however, they form a well-founded approach to slowing down these processes as much as possible, even over a service life extending far beyond the warranty period.

Our recommendation therefore remains unchanged: use high-quality, additive-free distilled water, keep the connectors clean and replace the coolant every three months.