Dead legs kill pipework
Undesirable, unnecessary and dangerous – dead legs are the forgotten pipe fixtures that serve no purpose but could end up costing you money this winter.
In pipe terms a ‘dead leg’ is the leftover stump of a former branch that was never fully removed. Dead legs are surprisingly common in even the simplest pipework systems and they require special attention when it comes to insulation.
One of the features of dead legs is that the water that flows through the rest of the pipework might do little to stir the water that ends up trapped in a ‘dead leg’.
Stationary water can provide a breeding ground for bacteria such as legionella. This is a serious consideration – pipe systems with plentiful ‘dead legs’ provide significantly less safe drinking water than a system with no redundancy at all.
With little to no water flow ‘dead legs’ are also critical weak points where pipe freezing is most likely to occur. Flowing water requires extremely cold temperatures before it will freeze but ‘dead’ water can freeze while the water in adjacent pipes flows, resulting in pipework systems that can freeze and burst in less than extreme conditions.
No dead legs to stand on
There’s no doubt that dead legs are a bad thing. WRAS, the water regulations advisory scheme who promote awareness and understanding of the water regulations, are very clear in their advice regarding dead legs. WRAS regulation 3 (2) (i) states that redundant pipework should be completely removed where possible and any ‘dead legs’ that can’t be practically removed should be no longer than twice the diameter of the pipe.
Almost all industrial operators have similar in-house rules regarding ‘dead legs’ but, despite this, dead legs remain and if you are responsible for operating an older water supply system you need to be prepared to take active measures to reduce the risks associated with the water in ‘dead legs’ freezing.
Trace heating & insulation
One way to mitigate against freezing is to apply trace heating specifically to the ‘dead leg’. Trace heating is energy intensive but it is the only way to guarantee that stationary water in pipework will not freeze. Pipe insulation is used in conjunction with trace heating to minimise energy loss and provide an emergency backup in case the trace heating cable were to fail.
The difficulty with insulating ‘dead legs’ is that these fixtures are often far more complex than linear pipes. Insulating offset ‘T’ braches or anchor legs can be tricky using rigid or semi-rigid insulation materials.
Kaiflex is a flexible insulation that’s easily fabricated to fit just about any shape or pipe configuration. Few other insulation materials are as appropriate for use on the complex geometry of ‘dead legs’ as Kaiflex and this is just one of the reasons why the material is so widely used by homeowners and industrial facility operators alike.