Dead Leg and its Limit in Water Systems

Dead Leg and its Limit in Water Systems

Dead leg calculation in water system piping and their limits according to world health organization (WHO).

Water system in pharmaceuticals may the source of contamination for the manufactured products. It is necessary to prevent the water system from microbial contamination.

Water is distributed through the pipelines throughout the manufacturing plant. Purified water and water for injection (WFI) is continuously circulated in the circulating loop. It helps the water system to prevent the formation of biofilms.

But there is some space between the circulation loop and the valve at the user points. This section of stagnant water is known as Dead Leg.

Related: Chemical Sanitization of RO Systems and Biofilm Removal 

Long dead legs will have more stagnant water having more microbial growth because the water in the dead leg does not circulate with circulating water. Therefore dead legs should be short.

According to WHO: TRS 929 (Page 54), dead-leg should not be more than 1.5 times 3 times (updated in TRS 970 page 83) of internal diameter (ID) of the pipe. Nowadays no dead leg pipelines are installed to solve the water staging problems in water systems.

Also see: Water Storage and Distribution System