Dead legs sound like something from sitting too long, but in water systems, they pose a serious risk. They cause water to stagnate and allow dangerous bacteria like legionella to grow.
What is a Dead Leg in Plumbing?
A dead leg is a section of water pipe rarely used, leading to a fitting such as an outside tap, boiler re-pressurisation hoses or shower heads. These are hard to spot without experience in the water system since they look like any other pipe.
The problem with dead legs is that stagnant water can allow bacteria like Legionella and Pseudomonas aeruginosa to grow. Even though they are not often used, dead legs remain connected to the water system, putting it at risk of bacterial colonisation.
Why are Dead Legs Dangerous?
Legionella and similar bacteria thrive in stagnant water. They can establish, multiply, and spread more easily in non-flowing water. A dead leg in a plumbing system lacks the regular flow found in active pipes, increasing the risk of stagnation.
Stagnant water encourages biofilm formation, providing nourishment and protection for bacteria. Once Legionella or other bacteria establish themselves in a water system, they form biofilms which spread and are challenging to eliminate. Preventing this is easier than trying to fix it later, so avoiding dead legs is important.
What is a Blind End or Dead End?
A blind end or dead end is a water pipe section closed at one end with no water flow. For instance, if a washbasin is removed and the hot and cold water pipes are capped off, the pipes will be filled with stagnant water.
What is the Difference Between a Dead Leg and a Blind or Dead End?
If you manage a building’s water system, be aware of blind ends, which differ slightly from dead legs. Blind ends are pipes connected to the system at one end and capped at the other. They often occur when a room’s use changes, such as converting a shower room into storage. The shower is removed, but the pipes remain capped, increasing the risk of legionella and other bacteria.
How do You Overcome Dead Legs in Plumbing?
To manage dead legs, it’s best to remove them. This also applies to unused blind ends. Start with a Legionella risk assessment for the water system. Consider the users and the system itself. Dead legs and blind ends present a risk in the assessment.
Take steps to eliminate or reduce these risks. Consider removing the pipework entirely. Even capped pipes can allow water entry, creating conditions for bacteria like Legionella and Pseudomonas aeruginosa to grow. This can affect the entire water system.
Removing dead legs and blind ends is always preferable. Guidelines suggest a dead leg or pipe should not exceed 1.5 times its width. Long pipes are not allowed in any building area.
How to Get Rid of a Dead Leg?
If you don’t know how to remove a dead leg, hire our experts to do it for you. Keep redundant piping as short as possible. A dead leg should be no longer than twice the width of your pipe. For example, a 15mm pipe should have a dead leg no longer than 30mm.
Cut off any dead leg longer than 100mm to prevent water stagnation and ensure safety. If you’re unsure about dead legs in your water system, contact us for a legionella risk assessment to help with your water compliance.
How often Should Dead Legs be Flushed to Control Legionella?
The UK Health and Safety Executive recommends removing all unused pipework. If you have dead legs that you rarely use, flush them every week. Thoroughly flush all taps, outlets, and shower heads weekly to control Legionella and other bacteria. Clean and disinfect shower heads and equipment at least every three months, ideally more often. In hard water areas, include descaling in your water hygiene routine.
Avoiding Dead Legs is Better than Dealing with Raised Legionella Levels
A professional Legionella risk assessment identifies dangerous dead legs or blind ends in your water system. Use this information to decide whether to remove them or keep certain ones in operation. This helps maintain workplace safety and water quality in your systems.
How do You Know you Have a Dead Leg in Your System?
Your legionella control program should include schematic drawings to show where dead legs are located. A legionella risk assessment will determine if these areas pose a risk and suggest actions to take. If removing the dead leg is not possible, conduct regular risk assessments to maintain water safety. Occasionally used water pipes that cannot be removed should be flushed regularly to prevent legionella bacteria from growing.
FAQs
What is the purpose of a dead leg in plumbing?
A dead leg is an unused section of plumbing or piping without regular water flow. This stagnant part can allow microorganisms, like Legionella pneumophila, to grow. This bacterium causes Legionnaires’ disease.
Can dead legs in water pipes affect my water bill?
Yes, dead legs can contribute to higher water bills because they may cause inefficiencies in your plumbing system. Even though the water in a dead leg doesn’t flow, it can still cause pressure imbalances, leading to leaks or the need for more frequent maintenance. Removing dead legs can help optimise your water usage and potentially lower your utility costs.
Is it expensive to remove a dead leg from my plumbing system?
The cost of removing a dead leg depends on the complexity of your plumbing system and the location of the dead leg. While it may involve some upfront costs for a plumber to assess and remove the pipe, the long-term benefits—such as improved water quality, system efficiency, and reduced health risks—often outweigh the remedial expense.
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