Water efficiency

- You may already know that over 70% of the Earth's surface is water, but did you know that only 1% of water available on Earth is suitable for drinking? The water efficiency category takes an efficiency first approach to water conservation with a goal to reduce potable water use. Many times, the environmental impact of water consumption is perceived as only depleted fresh water as a resource, yet it takes energy to treat water to drinkable quality, pump it through the pipes to buildings, and treat it once again, once it's used, in wastewater facilities. This is called water's embodied energy. Prerequisites and credits in the water efficiency category apply to outdoor water use, indoor water use, and specialized uses, such as cooling tower water use and metering. LEED addresses outdoor water use reduction with a prerequisite that sets a minimum reduction to water use for landscape irrigation. LEED addresses outdoor water use reduction with a prerequisite that sets a minimum reduction to water use for landscape irrigation. Once project teams meet this minimum requirement, they may target points for reducing irrigation water use even further, or eliminating it completely. Reduction strategies include plant selection, such as native plants, and efficient irrigation systems, such as drip irrigation instead of sprinklers. On many of my projects, we were able to eliminate the need for a permanent irrigation system by selecting native and adaptive plants. Indoor water use reduction is all about reducing water wasted by indoor plumbing fixtures, such as showerheads, lavatory faucets, and toilet flushing. LEED, Version Four, also includes appliance and process water use. This LEED prerequisite sets a minimum reduction. Most projects can easily achieve the requirements of the prerequisite by using fixtures readily available in the market. By reducing water use beyond this prerequisite, teams can earn multiple points. Some indoor water use reduction strategies include low-flow plumbing fixtures and use of non-potable water resources, such as rainwater, or gray water, which is water recycled from sinks and showers, to be used for activities such as flushing bathrooms. The water metering prerequisite and credit aims to support water management and identify opportunities for water savings by tracking consumption. The prerequisite calls for building-level metering, which most buildings already have through the utility companies. The water metering credit encourages advanced metering of major water subsystems, such as indoor plumbing fixtures, domestic hot water, or irrigation. In many occasions, advanced water metering pays back quickly in the form of water and sewer bill savings. Do you know how a cooling tower works? These systems remove heat by evaporating water. As the water absorbs heat, it evaporates. The more water evaporates, the more concentrated the dissolved solids become, and this may cause major issues, such as corrosion or scaling. To prevent this buildup, cooling towers deposit the remaining water, which is called a blowdown. Then, they repeat the process by taking in plenty of fresh water to make up for the losses through blowdown and evaporation. On many occasions, water used by cooling towers and similar equipment is potable water, thousands of gallons of it. The intent of the cooling tower water use credit is to reduce cooling tower makeup water use while controlling microbes, corrosion, and scaling in the condenser water systems. This can be done by increasing the number of cycles by treating water to remove dissolved soils. As you can tell, the water efficiency category is not just about reducing water use, but also about reducing energy spent to treat potable water and waste water. Here are the three key points in this category: use less, monitor what you're using, and look for ways to use alternative water sources that can replace potable water, when applicable. In the context of LEED, yes, water efficiency can earn points. But, from the perspective of humanity, our need for accessible, clean water is undoubtedly the most important thing to our survival, next to oxygen. Each and every one of our lives depends on it.