Health and Safety
February 22, 2024

DEAD LEGS – Why they should not be ignored

Does the term “dead leg” remind you of a thigh or knee injury? The “dead leg” we will be talking about in this blog couldn’t be more different. These dead legs are potentially dangerous plumbing errors that are frequently found in water systems; and if left unchecked, can lead to serious bacterial contamination problems.

A classic dead leg/blind end

If you are an owner or general manager of a business, it is your responsibility to make sure your water system is safe from the dangers caused by legionella and other waterborne bacteria. Identifying and managing dead legs is part of this responsibility. Of course, we don’t expect you to do it personally, just ensure it is done by a competent person.

What are dead legs in the water system?

Dead legs are difficult to identify because - knowledge of the water systems, and experience, are required to be able to spot them. A dead leg looks like any other length of pipework which forms part of the overall water system. The difference is that a dead leg is only rarely or never used.

    Conditions that create stagnant water in the system

As a rule of thumb, the maximum size of a dead leg should be no longer than 1.5 x its width.

Why are dead legs considered a risk?

A dead leg won’t have water flowing through it regularly, so any water in it is likely to stagnate. Legionella prefers stagnant water to flowing water, as stagnancy promotes formation of biofilm (slime), which provide both food and protection for bacteria. Once legionella establishes itself in the dead leg, it can easily spread further.

Example of a dead leg in the system
What is the difference between a dead leg and a blind end?

A blind end is a section of pipework that is closed off on one end, often created when a room is used for another purpose. For example, if a shower room is converted into a storeroom, the shower is removed, and the associated pipework is simply capped off, as this is the easiest solution. However, instead of removing the risks associated with the pipework, the risk is increased.

A blind end
How do you overcome dead legs in plumbing?

When dealing with dead legs or blind ends, the best option is always: Remove Them. We need to start with a legionella risk assessment which considers: 1) those using the water systems and (2) the system itself.

If the risk assessment identifies the presence of a dead leg or a blind end, the first thing you should ask yourself is – can it be simply removed? Even if it has been capped off, there is a chance of water getting in and creating conditions allowing legionella, pseudomonas aeruginosa, and other bacteria to thrive.

Removing and sealing a dead leg
How to deal with little used water outlets?

There may be situations where it is not be feasible to remove the dead leg, as it may still be occasionally used. Therefore, other steps must be taken to mitigate the risk.


In this case, it is recommended to flush through the pipework and outlets regularly to prevent stagnant water from pooling in the pipes and creating conditions for biofilms to form.

How often should dead legs be flushed?

o   If you have dead legs that are still in use, flush them through every week.

o   All infrequently used taps and shower heads must be thoroughly flushed weekly

o   Ensure you keep records of all weekly flushing, their locations and dates.

How can Nsure can assist you?

A professional legionella risk assessment can help identify dead legs or blind ends in your water system. Then you can determine whether removal is possible, and what must be done if certain dead legs cannot be removed. By focusing on the right course of action, you can maintain a high level of water quality and safety in your operations.

At Nsure, we support those responsible for the control of waterborne pathogens including legionella. We are experienced in delivering legionella risk assessments, water quality testing, independent compliance auditing, water safety training and other risk management services that help keep guests, employees and visitors safe.

Written by
Babli Jahau