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News & Press: Technical

Water Efficiency Standards and Equipment Requirements for Cooling Towers

Tuesday, August 22, 2017  

In June, the Austin City Council approved the adoption of the 2015 Uniform Mechanical Code and 2015 Uniform Plumbing Code including local amendments for water efficiency standards and equipment relating to cooling towers. The changes were in response to city council direction to implement these water conservation recommendations by citizen task forces in 2007 and 2014. The changes include requiring all cooling towers using Austin Water potable water to have:

  • make-up and blow down sub-meters;
  • a conductivity controller;
  • a drift eliminator with a drift rate of not more than 0.005 percent pf the circulated water flow rate in accordance with the manufacturer’s instructions;
  • an overflow alarm; and
  • achieve a minimum of 5 cycles of concentration. 

These requirements have been applicable to new and replacement cooling towers since January 1, 2008. As best management practices, most towers may already have some or all of the required equipment.  However, a complete retrofit, if necessary, is estimated to cost on average less than $10,000 with an average payback period of less than one year due to the significant savings in water and wastewater charges resulting from the retrofits.

For new and replacement cooling towers of 100 tons or greater combined cooling tower capacity, the new code provisions require that:

  • the make-up and blow down meters and overflow alarm must be connected to the building’s Central Energy Management System or Utility Monitoring Dashboard; and
     
  • the facility must have a water storage tank, plumbing and treatment system to either:
  1. utilize blow down water for wash down, cleaning, toilet flushing, landscape and other authorized purposes; or
     
  2. offset a minimum of 10% of the makeup water with reclaimed or onsite water reuse.  Due to high TDS levels, blowdown water for irrigation may need to be blended with rainwater or AC condensate to be suitable for the irrigation of plants.  Information about the beneficial reuse of blow down water can be found here. A summary of state regulations can be found at here. 

The code changes also include a requirement for owners of all cooling towers to register their towers with Austin Water and to submit annual inspection reports.  Existing towers have until December 31, 2017 to register their towers. New towers must register with Austin Water before operation. Registration forms will be available beginning September 6, 2017 on Austin Water’s web site and may be submitted electronically, by fax or by mail. 

The annual inspection reports must be on a form developed by Austin Water and be performed by an independent third party mechanical engineer or mechanical contractor. The first annual report is due to by March 1, 2018. The inspection will need to have occurred during the preceding 90 days prior to the March 1 deadline.

The cooling tower requirements seek to optimize the water efficiency achievable by existing systems using Austin Water’s high quality potable water with low Total Dissolved Solids levels if properly operated and maintained. The changes also seek to protect public health from potential airborne bacteria by eliminating drift and preventing water waste caused by the overflow from the cooling tower basin. 

Cooling towers must also meet these requirements to be eligible for Austin Water’s evaporative loss credit program, which provides a reduction in monthly wastewater bills for the amount of evaporated water from cooling towers not returned to the wastewater system. For more information about this program, call Austin Water’s Consumer Services Division at (512) 972-0000 ext. 4.

Rebates are still available under Austin Water’s Bucks for Business rebate program for water treatment and/or filtration systems that help a cooling tower achieve greater than five cycles; for alternative cooling systems such as Variable Refrigerant Flow systems that do not use potable water; or water treatment to increase the water efficiency of towers using reclaimed treated wastewater.  The rebate pays $0.50/1,000 gallons saved over a ten year period or 50% of the cost of the equipment, whichever is less, not to exceed $100,000.    

A workshop about the new requirements is set for September 27, 2017 (see related story in this newsletter).  For more information, visit Austin Water’s web site at www.waterwiseaustin,org or call (512) 974-2199.
 


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