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How to flush a deadleg

What is a Deadleg?

A deadleg is a pipe leading to an outlet through which water flows, but the outlet is unused or rarely used. As the pipe becomes isolated from the rest of the system, the water can often become stagnant within this section of the pipe. A visualization of a dead leg is shown in Figure 1.

Deadlegs can occur overtime as building occupancy and use changes. For example, if a sink or other type of basin was removed, the pipe work would just be capped off rather than removed completely. This is a deadleg.

Other examples of deadlegs include:

  • Lengths of Pipework That Have Been Blanked
  • Pumps Connected but Not Run
  • Taps Never or Rarely Used
  • Stagnant Tanks

Why Do They Need Flushing?

Due to the nature of deadlegs and the lack of use that they get, the water inside becomes stagnant. Stagnant water provides the ideal conditions for Legionella and other harmful bacteria to grow and multiply. If these bacteria become airborne and are inhaled, they could cause Pontiac fever, Lochgoilhead fever or potentially fatal Legionnaires Disease.

How to Flush a Dead Leg

Deadlegs need to be flushed regularly, to ensure that water within them does not provide ideal conditions for Legionella and other bacteria to grow. The frequency of flushing depends on the size of the deadleg, for example, some need to be flushed weekly.

To carry out the flushing, you need to put a flushing point onto the end of the deadleg. This can be either a manually operated valve or an automatic flushing point.

Hydraclean Ltd have designed an app, Delta Compliance Online, to ensure that you are flushing your deadlegs regularly alongside ensuring compliance for your business, building and/or client at all times.

Want to find out more about Delta Compliance Online and how it can benefit you, please email

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