FlushSafe keeps your sites L8 Compliant by automatically purging outlets based on temperate and stagnation, and provides remote logging for complete peace of mind.


Background to Legionella

Lots of people know about waterborne Legionella and how dangerous it can be, but few realise how prevalent it is. The bacteria responsible for Legionnaires’ disease multiply between 20-45°c when nutrients are available, offering a large window of opportunity for proliferation if systems are not managed correctly.

What is Legionella and Legionnaires’ disease?

Legionella is a pathogenic group of bacteria that cause pneumonia-type illnesses, with the most serious being Legionnaires’ disease.  You usually get it by breathing in mist from water that contains Legionella. The mist may come from hot tubs, showers, or taps in large buildings.

While most of those who are exposed to Legionella will not become ill, it’s still vital to ensure water systems and their constituent parts are properly maintained. To remain compliant, businesses need to assess risks in their networks, manage any identified issues, and then prevent the possibility of an outbreak. All of this work requires documentation to remain on the right side of the law.

How is it controlled?

To control Legionella, the temperature of a plumbing system can be maintained so as to prevent growth. The ideal temperature for Legionella is between 25-42°C, but when water is heated above 50°C, 90% of strains die. It is therefore imperative to keep the temperature above this threshold.

A heating loop is used to circulate hot water around a building and keep the temperature constant, however there are “legs” which must branch off in order to supply mixers to taps and showers. When these outlets have not been used for a while, the water in these legs converges to ambient temperature where Legionella thrives.

The potentially fatal consequences of serious contamination mean routine monitoring and inspection of at-risk areas is critical for those in charge of buildings. In no other environment is this more important than public washrooms, where complex circulating hot water systems are commonplace.

For some time, it has been recognised that failings in these environments often result from sub-standard risk assessments that overlook the different parts of a plumbing network. In response, Health and Safety Executive (HSE) has revised its own technical guidance document (HSG274 Part 2) to combat avoidable failings in Legionella control. Keeping compliant and free from bacteria will keep staff and customers safe from contaminated water. Legionella outbreaks can never be fully eliminated but they can be mitigated with the right procedures in place.

The Solution

To restrict Legionella growth, we should monitor the temperature of each leg 24/7 and automatically purge the outlet when the temperature drops below the temperature threshold. The leg most at risk is just downstream from the mixer (where the orange arrow is in the diagram).

We also install sub meters on each tap (indicated by “SM” in the diagram) so we can document the time and amount of water consumed on each purge.

Remote Purging

The ability to remotely purge each outlet, either manually or automatically based on pre-set rules and alerts, requires controlling a solenoid valve. These purging valves can be installed fresh on a separate branch specially routed for flushing a system of outlets to waste, or in parallel with tap/shower sensor valves which may already in use, to act as a bypass.

However, this requires significant plumbing and additional costs for fittings. Alternatively, if sensor valves are being used, we can retrofit our system onto these and use an “electronic bypass” instead.

By connecting an electronic bypass, we can allow the system to act normally for the majority of the time, but also have the ability to control the valve whenever we like. This could be done remotely by the click of a mouse, or dictated by rules such as time since last use and/or temperature level.

Typical Results

The chart for a typical configuration on a tap using 3 temperature sensors to monitor the hot, cold and warm water and a flow sensor is shown below. The graphs show the hot, cold and warm temperatures converging to ambient temperature each night when not used, highlighting the increased risk of Legionella growth.

Completely customisable and remotely controllable through your phone using

Remotely set up automatic purging from anywhere in the world

Email or SMS notifications
keep you in the know

Dynamic web dashboards –
see temperature and water usage in
real time

Secure access from any web
connected device using
bank-level SSL encryption

Ramp up purging thresholds remotely as site risk changes

Dedicated support from a
UK company

Fits to any valve, even the one there already


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