How To Treat Legionella in Water

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Legionella is a highly dangerous bacteria that causes a type of pneumonia called legionnaires’ disease.

If you’ve detected legionella bacteria in your water or you just want to minimize your legionella risk as much as possible, here’s what to do.

📌 Key Takeaways:

  • Legionella in water are harmful bacteria that could cause you to get sick with a lung infection called legionnaires’ disease.
  • Legionella bacteria aren’t commonly found in potable water systems, but if you detect legionella with a water test, you should act quickly to remove it from your water supply.
  • You can treat legionella in drinking water systems by addressing the root cause, shocking your water system, employing a suitable method of water treatment, an taking other steps to reduce the legionella risk in your home.

🦠 What Is Legionella & How Does It Contaminate Water?

Legionella is a group of bacteria that contaminate warm or stagnant water sources. The bacteria are most likely to grow in water with a temperature range of 77°F-113°F. Cooling towers, cold water storage tanks, building water systems, air conditioning units, and hot tubs all carry the risk of legionella growth.

Luckily, legionella is unlikely to be a problem in your own home. However, if you have detected these bacteria with a water test, you should look at methods of legionella control as soon as possible.

Drinking legionella bacteria isn’t usually dangerous. However, if your water system contains legionella, these bacteria will also contaminate the water vapor from your fixtures (such as showers and faucets).

Breathing in this water vapor is what causes legionella to enter your lungs, resulting in legionnaires’ disease.

Legionella in petri dish

📋 4 Ways To Treat Legionella In Water

Let’s take a look at the 4 most effective methods of treating legionella in your building water system.

Address The Root Cause

Ideally, you don’t want to have to install a water treatment solution to control legionella – you want to address the root cause and prevent legionella growth in the first place.

Legionella grows in stagnant water. So, assess your drinking water system and identify where legionella could have the opportunity to grow.

A few ways to reduce the likelihood of legionella growth are:

  • Flush out your infrequently-used water fixtures (including faucets and showers) once or twice a week.
  • Remove dead legs and dead ends in your plumbing system.
  • Clean and descale fixtures that carry stagnant water, including your showerheads and hoses.

Shock Your Water System

One of the most effective ways to kill legionella throughout your entire plumbing system is to shock the system with chemicals.

Shocking your plumbing involves adding increased levels of free chlorine, chlorine dioxide, or a similar water disinfectant to your water, then flushing these chemicals through all the pipes and fixtures in your home.

Identify the area that needs treatment before you get started. For instance, only your hot water system may need shocking.

There are a few things to keep in mind with this method of water treatment:

  • You should take all the necessary safety precautions, including wearing protective safety gear, when handling chemicals.
  • You shouldn’t drink water from your faucets until the chemical has been thoroughly flushed through the system and a water test shows that chemical levels are within a safe range.
  • Your state or local authority might have regulations (such as for drain discharge) that mean you can’t shock your water, or you can only do so with a permit.
Pouring chlorine to Springwell chemical injection system

Install A Water Treatment System

Another effective method of treating or controlling legionella in hot and cold water systems is to install a water filter or similar treatment system.

There are a few different systems that can effectively reduce, remove, or kill legionella bacteria in your plumbing:

Reverse Osmosis Systems

These water systems use membrane separation to remove contaminants as small as 0.0001 microns, including legionella (which are about 2-20 micrometers).

RO units are usually installed as point-of-use systems beneath kitchen sinks. They’re considered the best method of purifying water, by removing chemicals, heavy metals, microorganisms, and more.

Filling a glass from an RO system

Ultrafiltration Filters

These filters are similar to reverse osmosis, using a membrane with a pore size ranging from 0.02 to 0.05 microns to remove virtually all water impurities, including legionella.

The key difference between RO and UF is that ultrafiltration does not remove all dissolved impurities from water, while reverse osmosis does.

Other Microfiltration Systems

Any other types of water filters using microfiltration can also remove legionella, as long as the filter pore size is 0.2 microns or smaller.

These filters are known as microfilters and trap smaller contaminants than the average filter can remove.

UV Water Purifiers

These water systems don’t remove legionella from water, but kill legionella with UV light treatment, making them an attractive alternative to chemical treatment.

UV light penetrates the cell walls of legionella and damages their DNA, preventing them from reproducing or causing harm.

Depending on where legionella is detected in your water system, you might need to install one or several point-of-use water systems to control legionella in various water fixtures and outlets around your home.

For instance, you might need a POU filter to remove legionella at your showerhead, and another treatment system installed underneath your kitchen sink, to treat the water that leaves the faucet.

Keep in mind that installing a point-of-entry treatment system isn’t the solution if legionella grows at a later point along your plumbing system. Even if the filter kills or removes legionella when water enters your home, that’s no good if legionella can reenter your water supply later down the line.

Springwell blackcomb uv next to a water filter tank

Take Other Precautions

Aside from installing a water treatment system, there are a few other ways you can reduce the risk of legionella contamination in your home.

These include:

  • Make sure to keep up with the maintenance requirements for any humidifiers, air conditioning units, and other units that use water in your home.
  • Flush your hot water pipes regularly (at least once a week) to prevent the water from stagnating.
  • Clean and disinfect spa baths, hot tubs, and swimming pools as outlined by the manufacturer.
  • Regularly drain, clean, and disinfect any drinking water fountains in your home.
  • Wear gloves and a face mask when you’re using bagged potting mixes and soils for your garden, which may contain legionella bacteria.

Consider the ideal growing conditions for legionella: stagnant water, warm temperatures, not enough disinfectant residual from the water treatment plant, and excess nutrients, which all encourage biofilm formation.

While you might not be able to control some of these factors (such as the concentration of disinfectant chemicals your water utility uses), you can at least prevent water stagnation and various other water conditions in your home.

📑 Final Word

Fortunately, legionella is uncommon in residential properties, and you’re unlikely to get legionnaires’ disease from exposure to these bacteria at home. However, there are certain situations that make some people more at risk of legionella growth in their plumbing systems.

Using an effective method of legionella treatment should eliminate legionella from your home and greatly reduce your risk of legionnaires’ disease. If you’re concerned about legionella in your hot or cold water, contact your local water utility and consider testing your water for this dangerous bacteria.

  • Jennifer Byrd
    Water Treatment Specialist

    For 20+ years, Jennifer has championed clean water. From navigating operations to leading sales, she's tackled diverse industry challenges. Now, at Redbird Water, she crafts personalized solutions for homes, businesses, and factories. A past Chamber President and industry advocate, Jennifer leverages her expertise in cutting-edge filtration and custom design to transform water concerns into crystal-clear solutions.

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