Spot Free Water In a Hot Water Pressure Washer Coil

The Pitfalls of Using Spot-Free or Reverse Osmosis Water in Pressure Washer Heating Coils

Pressure washers are essential tools for maintaining a clean and spotless environment, but when it comes to choosing the right water for your pressure washer, caution is advised. Many operators are tempted to use spot-free or reverse osmosis water, thinking it will result in a superior clean. However, running such water through the heating coil of a pressure washer can lead to unintended consequences.

Corrosion Concerns

One of the primary reasons to avoid using spot-free or reverse osmosis water in pressure washer heating coils is the risk of corrosion. The lack of minerals in these types of water makes them highly aggressive, causing them to leach minerals from the metals they come into contact with. Heating coils, typically made of metals like copper or aluminum, are particularly susceptible to corrosion when exposed to demineralized water over time. This can lead to costly repairs or even the need for a complete replacement of the heating coil.

Reduced Heat Transfer Efficiency

Spot-free or reverse osmosis water has low conductivity due to the absence of minerals. This low conductivity can reduce the efficiency of heat transfer in the heating coil. The heating element relies on the minerals in the water to conduct heat effectively. When these minerals are lacking, the heating coil may struggle to reach and maintain the desired temperature. This inefficiency not only compromises the cleaning performance but also puts additional strain on the equipment, potentially shortening its lifespan.

Potential for Scale Buildup

While spot-free water is devoid of minerals, it can still contain dissolved gases. When this water is heated, these gases may be released, leading to the formation of scale deposits on the heating coil. Scale buildup can impede heat transfer, reducing the effectiveness of the heating element and ultimately diminishing the pressure washer’s performance. Regular descaling may become necessary, adding maintenance costs and downtime.

Impact on Pressure Washer Components

Apart from the heating coil, other components of the pressure washer, such as seals, O-rings, and gaskets, may be adversely affected by the use of spot-free or reverse osmosis water. The aggressive nature of demineralized water can accelerate wear and deterioration, potentially causing leaks and other issues that require timely repairs.


While spot-free and reverse osmosis water may be suitable for certain cleaning applications, it’s crucial to exercise caution when using them in pressure washers with heating coils. The potential for corrosion, reduced heat transfer efficiency, scale buildup, and damage to components outweigh the perceived benefits of spot-free cleaning. To ensure the longevity and optimal performance of your pressure washer, it’s advisable to use water with a balanced mineral content that won’t compromise the integrity of the equipment over time.