Keeping Your Building Safe: How to Test for Legionella in Water Systems

Dirty Cooling Tower

When Legionella seeps into a building’s water systems, it poses serious public health risks to building occupants. Knowing how to test for Legionella in water within a building keeps Legionella out and building occupants safe.

Signs of Legionella bacteria lurk in secret, hidden dark places until someone gets sick. But the onus is on building owners and building management to keep people safe. Many states have laws and regulations that enforce mandatory testing for signs of Legionnaires’ disease.

Building operations managers can prevent Legionnaires’ cases by adopting highly detailed and systematic water safety plans.

What is Legionella?

Legionella is a bacterium that occurs naturally in nature in ponds, rivers and lakes, but is also found in man-made water systems. The bacteria, which can cause Legionnaires’ disease, favors temperatures between 77 and 113 degrees Fahrenheit. Legionella dies quickly when temperatures are out of this range.

How can Legionella cause harm?

Exposure to Legionella bacteria can cause a serious type of pneumonia known as Legionnaires’ disease or a less serious illness called Pontiac fever. The elderly, smokers, heavy drinkers, those with chronic diseases and weakened immune systems are vulnerable to this potentially fatal pneumonia.

The illness does not spread from person to person. The primary route of Legionella infections is through airborne water droplets and waterborne pathogens in water supplies. Water sources within buildings are most likely to be the source of an outbreak of Legionnaires’ disease.

How does Legionella grow?

Legionella flourishes when stagnant water and biofilm exist within a facility’s water systems. Sediment, slime, algae, and rust all provide a place for Legionella to grow.

According to the CDC (Centers for Disease Control and Prevention) and the EPA (Environmental Protection Agency), Legionella can grow in water systems that are continually wet and warm, such as:

  • Hot and cold water storage tanks
  • Water heaters
  • Water hammer arrestors
  • Expansion tanks
  • Water filters
  • Electronic and manual faucets
  • Aerators
  • Faucet flow restrictors
  • Showerheads and hoses
  • Pipes, valves, and fittings
  • Centrally installed misters, atomizers, air washers, and humidifiers
  • Infrequently used equipment, including eyewash stations
  • Ice machines
  • Decorative fountains (water features) and hot tubs
  • Cooling towers
  • Drinking fountains

These systems release bacteria into the air posing a health risk. For instance, if Legionella is growing in restroom pipes, it releases into the air when someone turns on the faucet.

How to Test for Legionella

People can get extremely sick from minimal exposure to Legionella contamination. Quarterly testing of water quality parameters ensures water systems operate in a way that doesn’t allow bacteria to grow.

The CDC recommends performing an environmental assessment to identify areas of concern for Legionella growth. This assessment considers the factors that contribute to bacterial growth.

The next step is to develop a water sampling plan for the building water systems. The sampling plan covers locations identified in the assessment and develops a sampling schedule. According to the CDC, a 250 ml sample is sufficient for these test collections.

Should water analysis results show Legionella levels, poor water temperatures, or disinfectant residue, building operations teams can take corrective action to make conditions more acceptable. For instance, they can set hot water temperatures to the highest level allowed in state regulations or codes to stop Legionella growth.

They also can make sure disinfectant levels are detectable where water enters the building and at points of use. It is important to measure water pH to make sure the disinfectant is effective. Disinfectants work best within a narrow pH range.

Extra Steps

There’s no safe level of Legionella for water systems. Legionella cases have been associated with extremely low levels of Legionella growth. The best approach is to manage building water systems in such a way that Legionella cannot grow.

It’s important to make sure pipes, water systems and cooling towers are clean. Preventing and controlling buildup in mechanical and plumbing equipment saves money, reduces maintenance, prevents premature equipment failure, and eliminates places for Legionella to thrive.

Goodway’s ScaleBreak® liquid descaler  dissolves mineral deposits quickly, safely, and sustainably to keep water-cooled or heated equipment clean. The scale dissolves into liquid suspension technicians can flush from the system.

It is a bigger challenge to remove buildup in cooling towers which spread fresh and recycled air throughout the structure. These units are massive and always in use.

But cooling towers must be clean. Dirty cooling water can foul all waterside surfaces in a building. Left unchecked, dangerous bacteria can multiply, which can lead to an outbreak of Legionnaires’ disease. In fact, research shows cooling towers have caused almost half of all reported outbreaks of Legionnaires’ disease. Dirty cooling towers can become a deadly health hazard.

An aggressive cleaning plan coupled with training, monitoring, and testing helps prevent the spread of Legionella in cooling towers. OSHA recommends cleaning and disinfecting cooling towers at least twice a year; in the spring, before the cooling season begins, and after it ends in the fall.

Keeping cooling towers clean begins with monthly inspections where maintenance technicians inspect all surfaces for sediment, scale and biofilm (often referred to as slime). These inspections can identify problem areas where bacterium may thrive and multiply.

It is important to clean all basin surfaces regularly. Food and hiding places for bacteria are eliminated when slime, scale and sediment gets removed regularly. Goodway’s TowerVac makes monthly cleaning easier. The industrial vacuum can quickly remove mud, sludge, and bacteria from cooling tower basins without draining or shutting down the system.

A custom water treatment program manages water quality via a variety of treatments, including biocides, to keep Legionella bacteria at bay. However, it isn’t enough to keep cooling towers clean and clear of biological and scale buildup.

The cooling tower’s fill needs to be cleaned as well. Cooling tower fill is a medium that’s used to increase the surface area available for water. The fill can get dirty and full of scale buildup. Goodway’s TFC-200 combined with its ScaleBreak Gel descaling solution can remove scale, increase water flow, and control dangerous biological buildup in cooling towers.

Keep a record of all assessments, inspections and cleanings, water quality test results, operation and maintenance procedures. These records provide a baseline to help you detect when things are amiss and prove you did your due diligence should someone get sick.


Keeping water systems free of fouling ensures equipment operates as it should and keeps it free of harmful and dangerous biological buildup that can make people sick. Goodway offers cooling tower and water system cleaning tools, chemicals, and solutionss to keep systems clean and help you establish a regular maintenance plan. Call a Goodway Industrial expert to find out the best cleaning methods for your application.

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