Can Building Water Systems Be Both Healthy and Green?

Buildings cannot be healthy or resilient without successfully navigating the tension between building water safety and sustainability. Failure in the former could mean illness or death. Failure in the latter decreases efficiency.

People involved in managing buildings have been talking about water safety and building efficiency and sustainability for many years, but rarely in the same conversation or in the same room. One group talks about safety; the other about green buildings.

Conversations about water safety largely focus on water management programs (WMPs) designed to protect health and life and promote employee wellness. Conversations about green buildings may include minimizing water consumption, energy consumption, and materials.

This article is an invitation to discuss both important topics.

Background on Water Safety

Warnings about Legionella in cooling towers were issued shortly after the 1976 outbreak that affected more than 200 American Legionnaires and led to the discovery of the bacteria. Through the 1980s, studies performed by the Centers for Disease Control and Prevention (CDC) and universities found that Legionella presents a severe health risk, not just in cooling towers, but in other building systems and devices where it can grow and spread—domestic (potable) water systems, decorative fountains, hot tubs, industrial equipment.

Measures the researchers found to reduce Legionella—water system design factors, maintenance, operating procedures—became part of regulations and guidelines beginning in the 1990s. Australia and the United Kingdom established Legionella regulations in 1991. The EPA issued a warning document that year, too. OSHA released a guideline in 1996. Legionellae Control in Health Care Facilities: A Guide for Minimizing Risk, a book summarizing risk reduction measures based on scientific studies, was published in 1996. American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) began including Legionella prevention in its handbooks in the mid-1990s, issued a Legionella position statement and paper in 1998, and released the first version of its Legionella guideline (Guideline 12) in 2000.

In the United States, recommended Legionella preventive measures for building water systems other than cooling towers were largely ignored until ASHRAE finalized its Standard 188 in June 2015. To comply with ASHRAE Standard 188, a building with certain risk factors must implement a water management program (WMP) that effectively controls Legionella. In 2023, ASHRAE released Standard 514, which broadens the scope of building water management from controlling just Legionella to controlling all harmful microbes as well as chemical hazards and physical hazards (i.e., scalding).

Data from a 2021 study showed that ASHRAE Standard 188 water management programs can effectively reduce Legionella in domestic (potable) plumbing systems. Among the facilities studied, Legionella findings in plumbing systems decreased as control measure compliance (i.e., implementation on schedule) and water testing increased. The data indicate that the premise of ASHRAE 188 is sound—fully implementing a comprehensive WMP reduces Legionella and thus health risk.

However, a very small percentage of non-healthcare facilities have implemented an ASHRAE 188/514 WMP, which is likely why Legionella infections have not decreased since ASHRAE 188 was released. Legionnaires' disease has actually been on the rise, according to the CDC. For this reason, the CDC has urged state health departments to require water management programs. Regulations have been established in some states and are pending in others.

Conflicts Between Safety and Green Measures

Most Legionella control measures fit into one of the following categories:

• Minimize nutrients (biofilm, sediment)
• Minimize stagnation
• Minimize surface area
• Maintain a disinfectant residual
• Manage temperatures well

Some water safety procedures are not green. To minimize stagnation, the housekeeping or maintenance staff may flush all faucets and other points of use (POUs) for two minutes twice weekly, which uses a lot of water. The energy required to replace the hot water flushed is especially expensive. In some facilities, chemical disinfectants are added to the plumbing system to kill harmful bacteria. Recommendations also include running hot water recirculation pumps continuously, to keep water flowing.

And, some green measures can promote bacteria growth. Flow restrictors reduce flow, increase the spread of fine water droplets, and harbor sediment that provides nutrients for bacteria. Heat recovery systems may add surface area and stagnation to the system and present a significant risk if they are not completely separated from the domestic (potable) water system (e.g., via a double-walled heat exchanger). Water re-use systems (e.g., rainwater harvesting) may add nutrients and increase stagnation.

Measures That Promote Safety, As Well As Efficiency and Sustainability

Conversations about the intersection of safe water and green buildings typically focus on the above conflicts, but some measures support both objectives:

• Minimizing biofilm and scale is important for control of Legionella and certain other pathogens. It's also green: Just two millimeters of calcium carbonate scale and biofilm can increase energy costs by 50%, according to research by Montana State University.
• Minimizing piping, fixtures, and other equipment reduces the surface area onto which biofilm can develop. It also reduces materials and reduces energy losses from friction. One might wonder why a building owner would spend money to install unnecessary piping and equipment, but it is not uncommon. Water systems get over-engineered.
• Stagnant water, in addition to promoting pathogen growth, extracts metals and destroys building infrastructure via microbial induced corrosion (MIC). According to data published by Microbial Biotechnology in 2021, at least 20% of corrosion is attributable to MIC. Minimizing stagnation is therefore green in that extending equipment life ultimately means using less.

Automation Can Make Buildings Safer and Greener

To reduce health risk as well as water waste, energy consumption, and chemicals:

• Install sensors or smart faucets to minimize flushing. For example, if the facility aims to have all POUs used for at least two minutes twice weekly, water management software that is integrated with sensors or smart faucets can alert the facility personnel to flush only the under-used POUs rather than all POUs twice weekly. It saves water, energy, and lots of time.
• Install sensors to monitor water quality and make sure the sensors are integrated with the facility's water management program software. Staying on top of water quality problems may allow the facility to avoid chemical disinfection, or at least to reduce chemicals needed. For example, monitoring key water quality parameters at the point of water entry to the building can alert the facility of problems so that it can quickly respond. Responding quickly could prevent illness as well as fouling of the water systems that becomes very expensive to mitigate.

In sum, building water systems can be healthy and green. Building owners need to be educated, incentivized, and equipped to do both.