We growers are natural tinkerers. We’re always looking for ways to improve our gardens. Whether it is our gardening techniques or refining garden operations, we are always striving to learn and implement new things.

Being the masters of our plants allows us full control over their environmental conditions, including root zone temperatures. Although sometimes overlooked, providing optimal root zone temperatures is a great way of improving plant performance and production.

Utilizing a water chiller in your garden is one of the most effective ways of cooling root zone temperatures. While mostly used in hydroponic applications (DWC, RDWC, NFT, flood and drain), soil and other solid media gardens can also benefit from the oxygen-rich, consistent nutrient temperatures water chillers provide.

To understand how water chillers can benefit your garden, one must understand how root zone temperatures affect plant production.

Water Chillers and Root Zone Temps

Water chillers keep nutrient solution temperatures within the optimal range (65-70°F). This optimal range allows high levels of dissolved oxygen to be accessible to the root zone while also strengthening plant disease suppression.

A nutrient solution’s ability to hold dissolved oxygen diminishes as temperatures rise within the solution. This low-oxygen environment reduces the amount of oxygen available to the root zone, resulting in slowed growth and poor plant performance.

Combined with high temperatures, low-oxygen environments provide the ideal conditions for dangerous pathogens, such as pythium, to become established within a garden.

Water Chiller Overview

Much like other technologies within the ever-improving hydroponic industry, water chiller technology has come a long way. Affordable, efficient options are readily available to consumers. Gone are the days of being limited to expensive aquarium-specific chillers. With many choices to be made, it is important to choose the right water chiller that fits your garden’s needs and your performance expectations.

Water chillers work in conjunction with water pumps. As nutrient solution is circulated throughout the system/reservoir, the mechanics naturally heat the solution. This solution is then pumped through the water chiller, where it encounters cooling coils and is chilled to the desired temperature. This cooled solution is then circulated back into the system, providing ideal temperatures for explosive root growth and disease suppression.

Sizing

Here is a basic formula to correctly size a water chiller for your garden:

  • Calculate your total system volume (nutrient reservoir and any bucket systems)
  • Operate everything in the growroom (lights, fans, pump, humidifiers, etc.) and allow the growroom to reach its maximum temperature.
  • Once the growroom and nutrient solution have reached maximum temperature, cool the system/reservoir utilizing ice packs as the system runs.
  • Remove all ice packs from the system and continue to run for one hour. Once one hour has elapsed, take note of ending nutrient temp. Subtract the starting temp from the ending temp and plug all data into the following formula developed by Kevin Espiritu at Epic Gardening: total system volume in gallons x 8.34 (established weight of water) x starting and ending temperature difference = minimum BTU per hour needed

Example:

  • Total system volume: 100 gallons
  • Desired temperature: 68°F
  • Temp after one hour: 74°F
  • 100 x 8.34 x 6 = 5,004 BTU

Note as this calculates the minimum BTU required for this system, it is recommended to purchase a water chiller 20 per cent above the minimum requirement to make up for any performance loss. Also, choose a water chiller model that has a titanium heat exchanger to prevent any minerals from leaching into the nutrient solution.

Pros and Cons of Using a Water Chiller in Your Garden

So, is a water chiller right for your garden? Let’s look at the pros and cons for water chillers and discuss some alternatives.

Pros

  • High dissolved oxygen levels: The cool temperatures provided by water chillers can hold increased quantities of dissolved oxygen, the basis for explosive root growth and increased nutrient uptake.
  • Decreased risk of dangerous pathogens: Cool, highly oxygenated environments are a deterrent to many of the dangerous pathogens that can overtake a garden.
  • Heatsink: Cool solution can act as a heatsink, absorbing and cooling heat from growrooms.
  • Improving technology: Gardening-specific water chillers are flooding the market and continuously improving. Water chiller technology can also be seen in water cooled fans, reflectors, and CO2 generators, with some claiming to be 50 per cent more efficient than air conditioners.

Cons

  • Heat: Just like with all operational equipment, water chillers create heat. This requires them to be placed outside of the growroom or the creation of custom ducting to exhaust heat.
  • Expense: Although becoming increasingly affordable, water chillers are still an investment. Some growers may find it hard to justify the added expense of purchasing and operation.
  • Noise: Most of the equipment we employ in our garden create noise and vibrations. Water chillers are no exception. Their noise may be especially magnified by the fact they must be placed outside of growrooms.

Alternatives to Using Water Chillers

Still not convinced? Water chillers may not be right for your gardening situation. Here are some low-cost alternatives that can cool root zone temperatures.

Ice Packs: Cheap and easy, ice packs provide effective cooling in spot applications. While great for single reservoirs, they may be outmatched for cooling entire systems. They also take time to dial in and run the risk of root shock with too cold of temperatures. Be sure to have backup ice packs ready to go, as their cooling lifespan is limited.

White: Its well-known that white reflects light, which in effect reduces heat absorption, as light energy converts to heat. This phenomenon can be used to a grower’s advantage by painting reservoirs and any bucket system white. This technique can be an effective way of combating heat when used in conjunction with other heat reducing methods.

Location, location, location: Using a remote reservoir is a great way of reducing root zone temperatures. Growroom atmospheric conditions will quickly heat up any nutrient solution. Indoor reservoirs can simply be placed outside of the growroom. Outdoor reservoirs can be buried, along with any return lines.

Whether you’re a hydroponic or soil grower, root zone temperatures should be a priority. As it is one of the best ways of improving plant performance, water chillers are one of the most effective ways of producing optimal root zone temperatures. Figure out what works for you and your garden and experiment—it’s what we growers do best.