IBC Sl Series Installation & Operating Manual page 53

3.11.2 System piping
Closely-spaced tees: To avoid induced flow, each set of tees should be installed with
straight piping a minimum of 8 pipe diameters upstream and 4 pipe diameters
downstream, with no elbow or other component that may create turbulent flow. Tees
should be as close together as possible (maximum four pipe diameters apart) and there
should be no restrictions between the fittings that would result in a pressure drop.
Heat Migration: On secondary loops that extend vertically to a load that is above the
primary loop, use check valves on both supply and return of secondary piping.
Check valves or zone valves on return.
Figure 36 Primary-secondary piping details with closely-spaced tees
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