Using a water chiller for DWC can be essential to keeping reservoir temperatures down in warmer climates and in the summer. If you have ever suffered from root rot, you will know that warm reservoir temperatures are the achilles heel of DWC. As water temperatures increase, dissolved oxygen drops. Bacteria also multiply at an exponentially faster rate in warm environments. Think of a cold spring-fed trout lake VS a warm pond sitting in the sun all day. The pond will be full of bacteria while the cold spring fed lake will be crystal clear. The same idea applies to your DWC reservoir.
Since water chillers are expensive there are a number of things I suggest trying first, before buying a water chiller. I have grown in DWC for years without one, but I also live in a cold Canadian climate, and grow exclusively in basements/cold rooms and typically don’t grow indoors over the summer. While chillers are expensive if you’re growing in a warm climate investing in a water chiller could save you from root rot and the pain of a failed grow.
Overview
Choosing a Water Chiller for DWC
The following are my top two options when buying a water chillers for DWC:
- Active Aqua 1/4 HP 3,000 BTU
- DWC, rDWC, up to 10’x10′ grow area
- Active Aqua 1/10 HP 1,000 BTU
- Single DWC Reservoir, up to 3×3 grow area
If for some reason the Active Aqua units are unavailable, I have heard people have had luck with the chinese version of these chillers, though I do recommend going with the Active Aqua units if they available.
How Big of a Water Chiller do you need for DWC?
Trying to calculate exact cooling requirements can be very difficult due to the amount of variables present. You must factor in all the energy being introduced into the room, the insulation of your reservoirs, impact that aeration has on water temperature, evaporative cooling effect from the plants and so forth. As a rule of thumb a 3,000 BTU chiller will be able to bring your water temperature down by 10 degrees F in a 10’x10 room provided you have adequate reservoir insulation.
If possible always put the air pump and chiller outside of the grow room. The chiller will operate more efficiently in a cooler environment, and you won’t be heating the room you’re trying to cool.
How to Setup a DWC Water Chiller
You have two options when it comes to running a water chiller in a DWC enviornment
- Setup an rDWC system and chill water in the refill tank
- Use an extra large single DWC reservoir (e.g. ~70 Gallon tote in a 4×4)
To install the water chiller simply run an IN and OUT hose from your DWC reservoir to the water chiller. The chillers built in pump will circulate the water automatically until the target temperature is achieved.
Insulating the DWC Reservoir
If you are going to be chilling your reservoir it is a good idea to add insulation, otherwise you will get issues with condensation on the outside of your reservoir. Insulation will also increase the efficiency of your system, allowing the chiller to work less and saving on electricity costs.
The guys over a Zevk cultivation (a Canadian LP that runs rDWC at scale) use chillers and custom made coolers as their DWC reservoir. Just follow the instructions on how to build a DWC reservoir using a 70 quart cooler instead of a storage tote. Use a sheathing tape to seal off any exposed insulation when drilling through the cooler.
If you already have a DWC container or are running an rDWC system you may opt to simply add insulation to your container. I would recommend using something like SmartSHIELD for insulating, the 24″ roll is the perfect size for DWC reservoirs. It is not adhesive but can easily be secured to a DWC reservoir using Tuck Tape or Foil Tape. SmartSHIELD will act as a vapour barrier, which will prevent stagnant condensation from causing any potential mold issues.
Target Water Temperature for DWC
The target water temperature for your DWC chiller should be between 65-68F (18-20C). If running an rDWC system I would set temperature towards the lower end (65F), and in a single DWC tank application I would set temp closer to high end of the range (68F). Remember that water that is too cold can stunt plant growth. In the winter time I will use an electric heater to bring up my ground water up to temp before feeding the plants.
