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Weather and plant needs should dictate watering schedule
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July, 2010

By David Sim

Many property and facilities managers have taken steps to reduce obvious waste because it makes both financial and environmental sense to do so. Sometimes it’s not obvious, however. Overlooked systems in a facility can consume a significant amount of resources, but, once identified, can present an opportunity for savings.
 

  

Low-flush toilets, aerating showerheads and retrofits of cooling towers are often the first steps in a water conservation program. The landscape irrigation system should also be included.

A landscape irrigation system is literally an outdoor plumbing system of pipes and valves with hundreds of fixtures in the form of sprinklers. Most irrigation systems operate on a set-and-forget program that ensures it operates in the middle of the night, three or four times per week.

Typical irrigation operates whether or not it’s needed. Leaks, line breaks and waste can go undetected for years, causing infrastructure or landscape damage that may go unnoticed until the point when expensive repairs are required.
 
Many people are surprised by how much water those little sprinklers use. For example, one rotor-style sprinkler uses up to nine litres per minute for typically 30 minutes a night. That’s 810 litres per week when operating three times per week and 16,200 litres during a 20-week season – just from one fixture. A small 10-zone system with 10 rotors per zone will use 1.6 million litres per year.

Significant savings can be achieved by simply reducing the frequency of irrigation – i.e. not watering while it is raining or the day after it has rained – and eliminating overspray. A landscape irrigation auditor can help identify problem areas and recommend water saving technologies with surprisingly short paybacks. Some of those saving opportunities are evident at 75 Wynford Heights Crescent, a 24-storey residential condominium in north Toronto.

After completing an energy conservation review in 2007, property manager Melinda Cassar, of Brookfield Residential Services Ltd., began searching for other opportunities for conservation within the 28-year-old facility. Water consumption was identified as a concern that required further examination.

A water auditing firm was called in to evaluate the building’s irrigation system and determine if there was unrecognized waste in the system that could be eliminated. The complete audit of the irrigation system included a comprehensive equipment inventory and covered system static and dynamic pressure readings, existing programming and zone allocations, soil evaluation and infiltration rates, and micro-climate identification.

The resulting report highlighted the following key findings:
  • Numerous pipe leaks and breaks
  • Damaged or vandalized irrigation heads
  • Mixed precipitation rates                
  • Inoperative rain switch
  • System over pressurized by 50 per cent
  • Programming resulting in up to 600 per cent more water being applied than the soil can absorb.
The report also calculated that the daily and weekly irrigation schedule amounted to an annual water consumption of 6.9 million litres at a real life cost of $12 thousand per year. Meanwhile, the evaluation of the irrigation area, plant types, soil composition and micro-climates indicated that the amount of water required for a healthy landscape was more in the order of 2.7 million litres, which would cost less than five thousand dollars.

Put simply, the irrigation system at 75 Wynford Heights Crescent was using 300 per cent more water than the plants required, at an extra cost of seven thousand dollars per year. Following the irrigation auditor’s recommendations, the condominium corporation’s board and management elected to implement the following improvements to the system:
  • Rewrite programming to match soil infiltration rates
  • Match the precipitation rates of irrigation heads to approach uniform distribution
  • Install water-efficient nozzles that reduce overspray and eliminate drift
  • Regulate the system’s pressure to match the manufacturer’s specification
  • Install a centrally monitored irrigation controller that uses real-time weather data to set irrigation schedules and monitors system performance to identify and alert to equipment failures.
All work was completed by May 15th, 2009 and the results recorded over the duration of the irrigation season. Approximately 1.6 million litres were used in landscape irrigation over the course of the irrigating season – an amount less than estimated due to rainfall.

The investment paid for itself in less than one year.

David Sim is Director of Sales and Solutions with SMART Watering Systems Inc., the water auditor and irrigation system consultant at 75 Wynford Heights Crescent. For more information see the web site at www.smartwateringsystems.ca.		  
 
 
 
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