In this article, I want to take highlight the significance of water quality in heat pump systems by sharing some photos of a broken circulation pump. While there are several potential causes of damage, the most common culprit is often the cheapest component of the system: water.

I’m not a chemical engineer, but it’s clear that when dealing with water – the primary medium in an air-to-water heat pump system – and various materials such as copper, plastic and steel, maintaining proper water quality is essential.

The VDI 2035 guideline serves as the main standard for heating water treatment, though, in my experience, few people prioritise it. For a comprehensive guide, I recommend reading “Heating Water Treatment Explained” on the Heat Geek website.

The Role of Water Quality

Water quality is crucial for the longevity and efficiency of a heat pump system. Water with high levels of impurities, such as minerals, oxygen and certain chemicals, can lead to a range of problems:

• Corrosion: High levels of dissolved oxygen or improper pH levels can cause corrosion of the system’s metallic components. Over time, this corrosion can weaken pipes, heat exchangers and pumps, leading to system failures.

• Scale Formation: Hard water, which contains high levels of calcium and magnesium, can lead to scale deposits inside the system. These deposits restrict water flow, reduce heat transfer efficiency and increase the workload on the pump, often resulting in premature failure.

• Debris & Contaminants: Without proper filtration, debris can circulate within the system, leading to blockages and damage to the moving parts of the circulation pump, as shown in the images below.

The Impact on Circulation Pumps

The circulation pump is the heart of a heat pump system, responsible for moving water throughout the system. Poor water quality takes a toll on this critical component, often being the first to show signs of damage. The images provided illustrate several key issues:

• Impeller Wear: Contaminants in the water can erode or clog the impeller, which is vital for water movement.

• Seal Degradation: Poor water quality can degrade the seals within the pump, causing leaks and further mechanical issues.

• Internal Corrosion: Corrosion due to improper water chemistry can severely impact the pump’s efficiency and lead to complete system failure.

The Importance of Material Selection

In addition to maintaining water quality, choosing the right piping materials is equally important. Using incompatible materials can exacerbate system degradation. For example:

• Copper Pipes: While commonly used, copper can suffer from pitting corrosion if the water is too acidic.

• Galvanised Steel Pipes: These are prone to corrosion, especially in systems with poor water quality, leading to rust that can clog and damage pumps and other components. They are generally not recommended for heating systems, particularly when glycol is involved.

• Plastic Pipes: Materials like PEX or CPVC are often preferred in systems with water quality issues, as they are more resistant to corrosion and scaling.

Closing Thoughts

Maintaining proper water quality in your heat pump system is not just about ensuring efficient operation – it’s about protecting your investment. Poor water quality and inappropriate piping materials can cause significant damage to the circulation pump and other vital components, leading to costly repairs or replacements.

Regular water testing, the use of suitable filtration systems, and careful selection of piping materials are all essential steps in preventing these issues. By taking proactive measures, you can extend the life of your heat pump system and ensure it operates at peak efficiency.

Remember, a small investment in water quality maintenance today can save you from substantial costs due to system failure in the future.