Once-Through Cooling Equipment


Once-through cooling (OTC) systems, also known as single-pass cooling systems, consume significant amounts of potable drinking water, making them expensive to operate. On top of the cost of water, they also require a backflow-prevention device that requires annual testing. These systems use municipal drinking water as a means to remove unwanted heat, and then the water is directly discharged to the sewer. Common types of equipment that may use OTC include commercial and industrial walk-in coolers and freezers, air conditioners, wok stoves, and ice machines.

Switch now, save forever! Now is the best time to make the switch. The CRD Board has approved an amendment to the Water Conservation Bylaw (CRD Bylaw No. 4099) to prohibit the use of water for OTC. The amendment contains a five-year grace period, to allow time to plan for equipment replacement, and also allows for emergency use and applications for exceptions to be approved by the CRD. To help businesses in the capital region make the switch, the CRD is offering a rebate of up to $2,500 per water billing account to replace OTC condensers in a range of equipment.

OTC Rebate Program 

Water Conservation Bylaw Amendment

The CRD Water Conservation Bylaw (CRD Bylaw No. 4099) applies to any customers of the Regional Water Supply System in the Greater Victoria area, including residential, commercial, and institutional properties. Starting on July 1, 2028, no person shall use water in an OTC system unless the equipment is only operated in emergencies, or the person has obtained written authorization. For example, some equipment may have special requirements where no alternative is available. The bylaw allows for such exceptions as approved by the General Manager.

See our OTC FAQ below for more info on how to identify OTC, paybacks and best practices.

For complete Bylaw information, please refer to Bylaw 4099 - Capital Regional District Water Conservation Bylaw No. 1, 2016 (PDF).


Businesses in the capital region can receive a rebate of up to $600/refrigeration ton to replace once-through cooled condensers and up to $1,200/refrigeration ton to replace once-through cooled ice makers—plus, they’ll save more money every year with a less wasteful system.

How to apply

  • Complete and submit the Rebate Application Form (fillable PDF) by mail or email.
  • The CRD will contact the applicant to verify they meet the program requirements and provide a confirmation notice.
  • Complete the work using a licensed refrigeration and air conditioning mechanic.
  • Submit proof of work completion to the CRD.
  • The CRD may verify completion of work according to program requirements, then process the rebate payment.

For complete application and rebate procedure review the Rebate Application Form (fillable PDF).

Replacement options

  • Air-cooled equipment: install stand-alone air-cooled ice machines and condensing units.
  • Closed-loop piping: re-circulate cooling water to a remote air-cooled chiller or cooling tower, or connect to an existing closed-loop system serving another area of the building.
  • Split-system: use heat pumps with remote air-cooled condensers.
  • Remote air-cooled condenser: install an air-cooled condenser that vents outdoors.

OTC Frequently Asked Questions

How to Identify OTC

Any refrigeration system may be positively identified as OTC where it has a coaxial tube condensing coil connected to a domestic cold water supply and a drain (for any appliance with an enclosed refrigeration system that does not otherwise require a water supply or drain connection). However, air-cooled ice makers with self-contained refrigeration systems do require a water supply and drain connection for the ice production process, and are therefore difficult to distinguish from water cooled ice makers. One simple tip is that if the ice maker is Energy Star approved, it is air-cooled.

Typical examples of OTC equipment may include:

  • Refrigeration compressor units for walk-in coolers and freezers
  • Ice-making machines
  • Wok stoves
  • Server room cooling systems
  • Air conditioners
  • Heat pumps
  • X-ray machines
  • Hydraulic equipment
  • Degreasers
  • Welding equipment
  • Other industrial or laboratory type equipment

For a more in-depth look on identifying OTC, check out City of Vancouver's guide.

Payback on Replacement

The actual cost to eliminate OTC in a facility can vary widely depending on number, size, and types of OTC systems currently operating, as well as conditions that may prevent or complicate direct replacement with equivalent air-cooled systems. Typical payback periods for small commercial systems are as low as two years and with the rebate program, the payback period is further reduced!

For example, a typical small-medium OTC unit (1 ton, 12,000 BTU/hour, roughly 1 hp), with no maintenance issues uses approximately 6L/minute for an average of $6,600/year. These would typically run about 12 hours per day, which adds up to approximately 1,600 cubic meters per year per unit (enough to fill half an Olympic-sized swimming pool). By switching to an air-cooled unit, a facility can save about $4.21 per cubic meter (CRD water rate + CRD sewer rate) of water saved for a total annual savings of approximately $6,600.

Based on many retrofits that have been completed in recent years in Greater Victoria and Greater Vancouver, retrofit costs and utility cost savings are typically in the ranges shown in this Restaurant OTC Retrofit Fact Sheet. If you would like an estimated payback period for replacing the water cooled equipment, as well as realizing other potential savings for your business, please contact us by email or at 250.360.3103.

Proper Disposal of Decommissioned OTC Units

Equipment removed under the rebate program must have all chlorofluorocarbons (CFCs) removed (if applicable) and be recycled as scrap at: Schnitzer Steel Industries Inc., 307 David Street, Victoria, BC. A receipt is required.

Why Save Water?

While the reservoir may fill up quickly during rainy periods, drinking water usage doubles in the summer—primarily due to lawn and garden watering. With the effects of climate change, longer dry spells in the summer months and shorter, more intense rain events are expected. Having as much water storage in the reservoir as possible provides the assurance that not only will there be a sufficient quantity of drinking water for the year, but provides the flexibility to deal with drought and forest fires. Population growth will eventually require expansion of our water supply system, but ongoing water conservation can delay the costly expansion.

Replacing OTC in a Small Space with Limited Ventilation

An air-cooled unit requires ample cool air in order to operate effectively. Small, confined spaces particularly close to hot kitchens can cause excessive strain on an air-cooled system.

If your existing OTC unit is in a confined space, potential solutions include:

  • Improved ventilation to enable direct replacement with air-cooled equipment
  • Relocating the heat pump to a suitable location with adequate ventilation within the building
  • Installing a closed-loop cooling system where municipal water is used multiple times (i.e. re-circulated) before being discharged
  • Installing a chilled-water system where a chiller is installed on a rooftop or other exterior location. This is the most costly solution, typically applied when there are several OTC units located in a common area
  • For optimal utility savings where there are several OTC units, a closed loop or chilled water system can be combined with a heat exchanger to preheat domestic hot water for significant reductions in water and energy costs

OTC Best Practices

If you've identified OTC equipment in your business but cannot replace or retrofit the equipment in the near future, follow these tips to minimize water use:

  • Install solenoid valves that shut off cooling water when the equipment is turned off.
  • Regularly inspect existing solenoid or water control valves to ensure water is only flowing when there is a heat load to be removed. Improperly functioning valves can cost thousands of dollars per year in wasted water.
  • Use the minimum flow rate required to cool the system recommended by the manufacturer.
  • Insulate the piping, chiller and storage tanks for maximum efficiency.
  • Keep coil loops clean to maximize heat exchange.
  • Consider reusing cooling water to preheat water for other applications.


Water efficiency makes good business sense: replacing cooling systems saves you money and the regions valuable drinking water.

A typical small-medium sized OTC refrigeration unit uses about 1,600 cubic meters of water per year, enough to fill half an Olympic-sized swimming pool.

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