Design and Installation
06-236115-001 4-11 October 2014
4-2.3.2 Tee Flow Splits
Flow splits at tee junctions are sensitive to gravity. Even though turbulent flow exists, there is
a tendency for the vapor phase to migrate to the upper portion of the pipe leaving a more
dense medium at the bottom of the pipe. For this reason, the limitations in Figure 4-2 must be
observed.
4-2.3.2.1 Requirements for Tee Flow Splits
1. Bull head tees must have both outlets in the horizontal plane. The inlet to a bull head tee
may approach in a horizontal, vertically up or vertically down direction.
2. Side tees must have the inlet and both outlets all in the horizontal plane.
3. Elbows either before a tee, or after, which split to a separate hazard must be located a min-
imum distance of 15 pipe diameters (nominal) before the tee.
4. Tee splits going to separate hazards from a common supply line must be spaced a minimum
of 15 pipe diameters (nominal) apart.
5. Pipe reducers must be the concentric reducer type.
6. Minimum flow out of a side tee branch is 10% of total flow at the tee.
7. For flow splits less than 30%, the split shall be done through a side tee with the smaller
flow going through the side tee member. The minimum flow through the side tee member
is 10%. The maximum flow through the tee is 90%.
8. For flow splits equal to or greater than 30%, the split shall be done through a bull head tee.
The maximum flow split through a bull head tee is 70%.
4-2.3.3 Duration of Discharge
Per NFPA 2001, 2012 Edition, the liquid agent discharge shall be completed in a nominal 10
seconds or less. Discharge times shorter than 10 seconds are desirable to minimize production
of breakdown products. Discharge times as short as six seconds should be considered when
circumstances permit.
Table 4-6. 15 Pipe Diameters
Pipe Size
15 Pipe Diameters
feet feet and inches meters
1/2 in 0.63 7½ in 0.192
3/4 in 0.94 11¼ in 0.287
1 in 1.25 1 ft 3 in 0.381
1¼ in 1.56 1 ft 6 ¾ in 0.475
1½ in 1.88 1 ft10½ in 0.573
2 in 2.50 2 ft 6 in 0.762
2½ in 3.13 3 ft 1½ in 0.954
3 in 3.75 3 ft 9 in 1.143
4 in 5.00 5 ft 1.524
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