When do you need a water flushing regime?

By: James Greenwood on Jan 11, 2021

Duty holders have a responsibility to prevent or control the risk of exposure to Legionella bacteria, which can lead to the potentially fatal Legionnaires’ disease.

Of course, the best answer is to engineer and maintain a system that is always up to temperature and always running regularly through all outlets. But in some cases, that is not possible and the recent local, national and fast changing lockdowns and tiering have provided more of a challenge in ensuring that building water temperatures are kept correct and water does not stagnate.

The most common form of defence against Legionella is to control the temperature of the water. Hot water temperatures must be above 50°C within 1 minute of opening and outlet and cold water temperatures below 20°C after 2 minutes of opening the outlet. There are variations for Healthcare environments and of course for mixed or blended outlets where the water coming into these devices should adhere to these temperatures.

Systems may have challenges in maintain temperatures for a variety of reasons. Engineering out the problem may not practicable, or as a reaction to events such as lockdowns, in which case it may be necessary to implement a flushing regime. Stagnant water is a breeding ground for Legionella bacteria. Flushing the hot or cold water system will help ensure that the water is kept flowing, up to temperature and doesn’t stagnate.

In this blog post, we take a closer look at why a flushing regime should be considered in every organisation’s water safety plan - and what it entails.

What is flushing?

Flushing is a method undertaken to prevent the build-up of conditions favourable to the growth of Legionella and other bacteria within hot and cold water systems. It does this by:

  • Introducing fresh cold water containing residual disinfectant
  • Exposing pipework to temperatures at which Legionella bacteria is discouraged
  • Dislodging biofilm through the simple act of running water

A flushing programme should be designed so that it allows for the whole dead-leg (section of stagnant water) to be removed.

The water should be purged long enough for circulating or freshwater to be drawn from the outlet - indicating that all stagnant water has been expelled.

How often should flushing be done?

In most cases, flushing should be carried out at least weekly in order to reduce the risk of Legionella and other bacterial growth.

But in high-risk populations such as healthcare facilities and care homes, a risk assessment may indicate the need for more frequent flushing - i.e. twice weekly.

Flushing may also be increased when the water system is not used for seven days or more, i.e. during the temporary closure of buildings or departments. The length of purge and the way the flushing is done may also need to be extended, for example, turning taps and showers on for two minutes, preferably at a high temperature and from multiple locations at the same time to mimic normal usage.

Why is it important for Legionella prevention?

Legionella bacteria can lead to Legionnaires’ disease, which can symptoms such as a high temperature, dry cough, muscle aches and headaches. And in some cases, it can be fatal.

Companies have been fined millions of pounds when Legionnaires’ disease has resulted in a fatality. In 2018, a care home provider was fined £3 million after an elderly man died at one of its nursing homes. The failure to flush and disinfect pipes following refurbishment works was declared as the most likely cause of the infection.

The importance of flushing has been a popular topic of discussion during the coronavirus pandemic. Reduced building occupancy due to lockdown restrictions has highlighted the need for increased flushing to protect the water quality.

Research by WCS Group revealed how the effect of lockdown is having a negative impact on water quality - a 20% increase in positive Legionella sample results have been returned on a like for like basis from independent, UKAS Accredited laboratory testing.

Flushing best practice

Turning on a tap might sound easy, but it is important to follow best practice when flushing:

  • Water released from the outlet during flushing should be purged to drain safely
  • Flushing should be carried out in a safe manner which minimises aerosol production
  • Hard-copy or electric records should be recorded, including a list of the individual outlets flushed; the date, time and duration of flushing; biocide concentration; any other observations; and the initials of the person carrying out the work
  • Training is likely to be required for personnel carrying out flushing activities, as well as those supervising them

Having a system in place to help you identify outlets that are used infrequently is also very important. This may mean involving others within your organisation to find out how often outlets are used, as well as designers and installers.

Flushing of outlets is essential because it is key to preventing stagnation. However, a water flushing regime should form part of a wider approach to Legionella prevention and water treatment in general.

Water Treatment

James Greenwood

Written by James Greenwood

James Greenwood as been working in the Water Treatment and Water Hygiene Industry for over 20 years. He is currently the Sales and Marketing Director for WCS Group the largest water hygiene and treatment Company in the UK. James has been instrumental in bringing significant innovations to the UK market over the years always focusing on enhancing client’s compliance and delivering true return on investment projects offering monetary and environmental savings.