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By: FlowGuard EMEA on 05-sep-2022 1:00:00
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5 Dangers of Legionella You Should Know

Understanding the dangers of one of the most common waterborne diseases and how plumbing pipes contribute to the spread of legionella in the home.


When bacteria build to dangerous levels, waterborne diseases can thrive. FlowGuard CPVC (chlorinated polyvinyl chloride) smooth wall helps to minimise build-up of bacteria like legionella, in hot and cold water supply lines.


What's Legionella bacteria?

Legionella is a well-known waterborne bacteria which, when ingested via close contact with water or soil, can cause legionnaires disease or Pontiac Fever. Legionnaires disease is a form of pneumonia, whereby infection from the legionella bacteria leads to lung inflammation. Symptoms can range from mild flu like experiences to life-threatening respiratory problems.

Let’s discuss the ways in which legionella pose a risk in plastic water pipes, the real ways in which those risks can prevent themselves, and most importantly, what we can do to prevent it through modern plumbing standards.

Where can legionella grow?

  1. Legionella grows inside plumbing pipes via biofilm.

The common domestic plumbing pipe can be the ideal aqueous environment for biofilm to thrive.

Biofilm is a sticky, glue-like substance which develops quickly in water distribution systems and can even be encouraged by plumbing pipes themselves.

Commonly used PPR plastic pipe for example, is made from organic materials which encourages the presence and development of bacteria. 

FlowGuard CPVC has an inherent pipe smoothness that causes waterborne bacteria to struggle to take hold. Chlorine is used in disinfectants; these disinfectants can damage some plastics, but will not adversely affect CPVC. 

Can legionella grow in cold water?

  1. Legionella thrives in wet environments where biofilm can attach.

Wet environments such as plumbing pipes are instrumental in the legionella development process.

First, the wet environment provides natural sustenance for multiple bacterial types to grow. Secondly, the flow of water through this environment naturally "picks up" bacteria when biofilm has reached optimum size. This is how dangerous pathogens can be easily and unknowingly delivered via the water supply.

Can legionella survive in hot water?

  1. Hot water can kill legionella, but it thrives in warm water.

Legionella cannot survive temperatures above 60° C. However, warm temperatures used in domestic environments are of greater risk to homeowners.

Temperatures between 25° C and 40° C not only cause no harm to legionella, but it can actually encourage accelerated growth.

This makes the selection of pipe even more important, especially when a range of temperatures are required. For example PPR's maximum operating temperature is 70°C, while heat resistant FlowGuard CPVC can carry hot water up to 93°C.

Can legionella survive in chlorinated water?

  1. Chlorine can damage plumbing pipes and provide a place for bacteria to grow. 

While chlorine and chlorine dioxide are essential to the prevention of microbial contamination during water treatment, it can actually be a risk to water supply lines made from PPR.

PPR pipes risk long-term damage from ordinary levels of chlorine, and do not resist chlorine dioxide at all (widely used lately due to its disinfecting capabilities and low cost) degrading the plastic tubing, creating uneven surfaces and inviting biofilm to grow faster.

Highly durable FlowGuard CPVC is engineered with higher levels of chlorine, creating a smooth surface, consistent wall thickness and inherent corrosion resistance to chlorinated water, eliminating the risk of degradation due to natural levels of chlorine in the water pipes.

Which pipe material resists legionella the most?

  1. Some pipe materials can greatly increase the risk of legionella.

According to KIWA water research, the legionella bacteria present in water supplies can vary greatly from one pipe to another.

As you can see below, the legionella found in PPR piping is significantly higher than that of CPVC, PEX pipes and even steel pipe. This is due to the biofilm potential that PPR has over CPVC.

Study: Bioflim Formation Potential of Pipe Materials in internal installations by H.R. Veenendaal / D. Van de Kooiy – KIWA - 1999

It is therefore essential when installing or upgrading plumbing systems that property owners seek out professional test results for their selected pipe material, even the most rigid plastic pipes.

Learn more

For more advice on selecting the best pipe material for home plumbing systems and to understand more about the risks of contamination in home water supplies, download our free Homeowners guide to CPVC.