Corrosion is one of the most common—and at the same time most expensive—causes of damage in heating systems.
It develops quietly, insidiously, and often goes unnoticed for a long time. By the time the first signs become visible, the damage is usually already well advanced.

Yet corrosion is not an inevitable fate.
It is the result of specific environmental conditions—and can therefore be specifically prevented if these conditions are properly managed from the start.

Corrosion is not a coincidence, but chemistry

In heating systems, water is not a neutral filler but a chemically active operating medium.
It is in constant contact with metals, seals, and heat exchangers and affects their condition over the years.

Corrosion always occurs when:

the heating water is chemically unstable
unfavorable pH values are present
conductivity is too high
Oxygen enters the system

These processes occur continuously—regardless of whether the system is currently operating at full load or partial load.

Why modern heating systems are particularly sensitive

Modern heating systems operate more efficiently, are more compact, and involve more complex materials than earlier systems.
This has many advantages—but at the same time increases the demands on water quality.

Common examples today include:

Aluminum or stainless steel heat exchangers
mixed materials in the piping network
High temperature differentials
Low water volumes

These systems are significantly more sensitive to chemical imbalances.
Corrosion does not progress more slowly here—but is often more targeted and destructive.

Conductivity: the underestimated driver of corrosion

Electrical conductivity describes how many dissolved ions are present in the water and how well the water can conduct electrical currents.
It is therefore a direct indicator of the water’s “activity level” from an electrochemical perspective.

The higher the conductivity, the more dissolved salts—and thus potentially reactive components—are present in the system.
The water becomes more conductive—and at the same time more reactive.

The result: electrochemical processes proceed faster and more intensely.

In practice, this means:

increased susceptibility to corrosion throughout the system
intensified electrochemical reactions on metallic surfaces
Accelerated material degradation, particularly on sensitive components

High conductivity is particularly critical in systems with different materials.
For example, when steel, copper, or aluminum come into contact with one another, galvanic cells can form. The conductivity of the water acts as a “transport medium” for electrical charges and further intensifies these processes.

What happens in detail:
Electrical voltages arise between the metals, which are balanced out by the conductive water. In the process, metal ions are released from less noble materials—corrosion occurs.

This is precisely why conductivity is not a “secondary factor,” but a key control parameter in heating and cooling water systems.

If you don’t keep an eye on conductivity, you lose control over the electrochemical processes in the system.

Or to put it another way:

👉 Conductivity significantly determines how “aggressive” water is within the system.

The targeted reduction and continuous control of conductivity is therefore a crucial component for sustainably preventing corrosion and ensuring the system’s service life.

The pH value determines material compatibility

The pH value is one of the key control parameters in heating and cooling water systems.
It determines whether water has a neutral, protective, or corrosive effect on the materials used.

It is important to understand that:
The pH value does not act in isolation, but always in conjunction with conductivity, materials, and operating conditions. Even small deviations can have significant long-term effects—often without the system initially showing any noticeable reaction.

This is precisely what makes the pH value so critical.

If it falls outside the recommended ranges, insidious processes develop that only become apparent after a delay. The system appears to be running stably, while material corrosion is already taking place in the background.

Typical risks include:

pH value too low
→ increased solubility of metals
→ increased corrosion, especially in steel and iron
pH value too high
→ Attack on sensitive materials such as aluminum
→ Damage to seals and non-metallic components

This becomes particularly problematic in mixed systems. Different materials react with varying degrees of sensitivity to pH deviations. A value that is not critical for one material may already be harmful to another.

This is precisely why blanket target values often fall short in practice.

The optimal pH range always depends on:

the materials used
the system configuration
the applicable guidelines (e.g., VDI 2035)

Maintaining a stable pH value is therefore not a one-time measure, but an ongoing task in plant operation.

Or to put it another way:

👉 The pH value determines not only the water quality—but also whether materials are protected or corroded.

The targeted adjustment and long-term stabilization of the pH value is thus a key factor for material compatibility and the service life of the entire system.

Oxygen: the catalyst in the system

Oxygen is one of the most potent drivers of corrosion.
It enters the heating system through:

Filling
Make-up
Leaks
open system components

Even small amounts are sufficient to trigger corrosion processes.
The combination of oxygen and high conductivity is particularly critical.

Preventing corrosion therefore also means:

Minimize makeup water
Ensuring tightness
Maintaining stable water quality

Make-up water as a common source of error

Many heating systems are initially filled correctly—but gradually lose water quality during operation.
The most common reason for this is uncontrolled makeup water.

Every liter of untreated water introduces:

new salts into the system
additional oxygen
changes in pH levels

These inputs do not have a one-time effect, but rather a cumulative one. Over months and years, conductivity increases, the pH value drifts, and corrosion processes are accelerated.

It is particularly critical that makeup water is rarely documented or monitored in practice.
Even a professionally performed initial filling is thus gradually rendered ineffective.

The only remedy is a consistently planned makeup water concept.
With a solution like Heaty Complete PROfessional, every water top-up is automatically treated and monitored before the water enters the heating circuit.
This keeps water quality stable—regardless of how often or for what reason make-up is performed.

Top-up thus transforms from a risk into a controlled, safe process.

Heaty Complete Professional

Heaty Complete PROfessional is the world’s first smart IoT make-up system, including Cloud connection – fully automatic, leakage protection and digital water meter.
To the product

Treatment instead of repair

A common misconception in practice is that
heating water treatment is a measure taken only in the event of damage.

Yet its greatest benefit clearly lies in prevention.

Targeted heating water treatment:

reduces conductivity
removes corrosion-promoting salts
Stabilizes the pH value
creates operating conditions compatible with the materials

This prevents corrosion processes from occurring in the first place—rather than having to combat them later at great expense.

Treatment units such as the Heaty Ferriline No. 2 are designed precisely for this preventive approach.
They enable controlled desalination and stabilization of the heating water, thereby creating the chemical foundation for long-term, safe system operation.

Those who only react once damage is visible are acting too late.
Those who treat the water early on prevent repairs instead of managing them.

Heaty Ferriline No. 2

Complete unit for professional bypass treatment, sludge and magnetite filtration in the hot water area incl. MAGella twister
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Regular analysis ensures control

Corrosion does not occur suddenly.
It announces itself through changes in water parameters—long before components fail or malfunctions occur.

Regular heating water analyses enable:

das frühzeitige Erkennen kritischer Abweichungen
targeted, timely countermeasures
Comprehensive documentation of the system’s condition

This transforms corrosion protection from mere damage control into a controlled, predictable process.

What matters here is not just the measurement itself, but its reliability and documentation.
With a measuring device like the WaterBoy, pH and conductivity can be reliably measured and recorded directly in a structured report.

This creates transparency regarding the condition of the heating water—both technically and legally—and changes no longer go unnoticed.

Messkoffer WaterBoy

The UWS WaterBoy measuring case contains everything the HVAC specialist needs to measure data in accordance with the VDI 2035, ÖNORM H 5195-1 and SWKI BT 102-01 standards in two L-BOXXES.
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Think holistically instead of treating symptoms

As all solutions from UWS Technologie demonstrate, corrosion can only be permanently prevented if all influencing factors are considered together.

This includes:

Appropriate water treatment
Carefully selected materials
controlled replenishment
regular analysis
clean documentation

Individual measures fall short—the key lies in the interplay.

Conclusion: Corrosion prevention is predictable

Corrosion is not an inevitable aging process.
It is the result of unstable water chemistry—and therefore controllable.

Who:

Treats heating water in a targeted manner
Keeping an eye on conductivity and pH
Minimize oxygen ingress
Controlled replenishment
Regularly analyzed

creates the basis for:

Long-lasting heating systems
Stable efficiency
Lower maintenance and repair costs
High operational reliability

Preventing corrosion means taking responsibility for the entire life cycle of the system.

Preventing corrosion: How to protect heating systems long-term and avoid damage