Dead legs will be measured by the term L/D, where L is the leg extension from the I.D. wall normal to the flow pattern or direction, and D is the I.D. of the extension or leg of a tubing fitting or the nominal dimension of a valve or instrument. For valves, L shall be measured to the seal point of the valve. If a branch from a primary pipeline has demonstrated flow during cleaning and SIP, it does not constitute a dead leg.For high purity water systems, an L/D of 2 or less is attainable with today’s manufacturing and design technology. For other bioprocessing systems, such as purification, filtration, and fermentation having cluster, block, and multi-port valves, an L/D of 2 or less is achievable. However, it may not be achievable with certain equipment and process configurations as they are currently manufactured. For this part, an L/D of 2 or less shall be considered a target ratio, and shall not be construed to be an absolute requirement.