Why Your Small Pool Needs a Big Chiller

Most people assume that smaller pools require smaller chillers. It’s logical—less water should mean less cooling power needed. But installers across Australia are discovering the opposite is true.

We recently spoke with one of the country’s largest cold plunge installation companies. They shared that they’re moving away from recommending small tubs because they’re harder to keep at a consistent temperature, that was until they started using our chillers.

The Physics Behind the Problem

The issue comes down to thermal mass and heat transfer. Smaller bodies of water respond more dramatically to temperature changes because there’s less water to absorb the heat input.

Consider this: if you pour a cup of hot water into a half-full cup of cold water, the temperature spikes dramatically. Pour that same cup into a bathtub, and you’ll see a tiny increase. Add it to a backyard pool, and the change is barely noticeable.

This principle applies directly to cold plunge pools. When someone enters a small pool, their body heat can raise the water temperature by 2-3 degrees instantly. Ambient heat from the room adds another degree. Each input creates a proportionally larger impact in smaller volumes.

Real-World Implications

Smaller pools face constant temperature fluctuations from:

• Body heat from users
• Ambient room temperature
• Air circulation patterns
• Equipment heat

These factors create a cycle where the chiller works harder and more frequently to maintain the target temperature. The constant on-off cycling puts additional stress on the equipment and leads to higher energy consumption.

The Solution

To handle these rapid temperature swings, smaller pools need chillers with higher capacity and faster recovery times. The chiller must be powerful enough to quickly bring the water back to temperature after each disturbance.

This means a 500-litre pool might need the same chiller capacity as a 2000-litre pool, simply because of the volatility factor. The smaller pool requires more aggressive cooling to maintain stability, espcially with the same volume of swimmers.

Planning Your Installation

When sizing a chiller for your cold plunge, consider:

• Expected usage patterns
• Room temperature and ventilation
• Insulation quality
• Target temperature consistency

The goal isn’t just reaching your target temperature—it’s maintaining it consistently despite regular disturbances.

Understanding this principle can save you from undersizing your chiller and dealing with temperature fluctuations that affect your cold plunge experience.