What is a dead leg? And How Do You Know If You Have One

In terms of your company’s water system, a dead leg is a section of piping that is no longer used, or rarely used. It is generally created when modifications have been made to the system and piping removed, leaving a small ‘leg’ that is capped.

Without having water flushing through it on a frequent basis, a dead leg will collect stagnant water, so the extra pipework needs to be made as short as possible and capped. A further danger of a dead leg is that, without movement, water is more likely to settle at a temperature that favours the legionella bacteria, creating the kind of conditions that will enable it to thrive.

How do you know you have a dead leg in your system?

As part of your legionella control programme, schematic drawings will map out where any dead legs occur. Getting a legionella risk assessment will identify whether these legs are a risk and recommend any remedial action you can take. If for any reason, it is not possible to remove the dead leg, you will need to do regular risk assessments to ensure water safety. In rare circumstances, a water pipe is used only occasionally and therefore cannot be removed, in which case you need to regularly flush water through it in order to help prevent the legionella bacteria from being able to take hold.

How to get rid of a dead leg

If you are unsure of how to get rid of a dead leg, hire a professional plumber to do the task for you. The length of redundant piping must be as short as possible. In fact, the Water Regulations Advisory Scheme (WRAS) recommends that a dead leg must be no longer than twice the width of your pipe, for example, a 30mm dead leg for a 15mm pipe. If your water system has a dead leg that is more than 100mm, you must cut off the excess in order to prevent the water from stagnating and to ensure the water remains safe.

If you are unsure about dead legs in your water system, contact us to arrange a legionella risk assessment or talk to us about our other services.