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Plumbing Design Assistance Manual | Appendix C – Fitting equivalent length l 101
Appendix C:
Fitting equivalent length
Equivalent length
of ttings
This section provides the
equivalent length of piping
pressure loss for several
ProPEX ttings. The
equivalent length is used to
approximate the impact the
ttings have on pressure loss
across the piping length. The
equivalent length for each
tting is shown in the tables
below. Add the equivalent
length to the total piping
length for each tting installed
along the piping run. The
total pressure loss is then
computed from the adjusted
total piping length. Equivalent
lengths are commonly
utilized to calculate the Total
Developed Length (TDL)
along a critical piping path.
All Uponor values represent
pressure loss at 8 ft./sec.
Many methods exist for
calculating the coefcient of
velocity (C
v
) across valves and
ttings. The proceeding set of
Uponor data was derived from
empirical testing performed
by NSF International and
tested to ISA-S75.02 Pressure
Drop Measurement and C
v
Calculations at a measured
and veried ow rate. In order
to calculate equivalent length
in feet, a quadratic equation is
utilized to determine pressure
drop versus ow data at
precisely 8 ft./sec.
Other common methods for
calculating C
v
include UL 1821
Thermoplastic Sprinkler Pipe
and Fittings for Fire Protection
and the use of ow modeling
software. Through extensive
testing and validation by NSF
International, Uponor has built
a complete and accurate data
set for AquaPEX plumbing
systems. When comparing
equivalent length data across
PEX tting manufacturers,
values may differ due to
different testing methods and
reported values at specic ow
velocities other than 8 ft./sec.
For comparison purposes,
NSF International tested
commonly available ASTM
F1807 Brass Insert Fittings
Utilizing Copper Crimp Ring
for PEX Tubing Fittings and
ASTM F2159 Plastic Insert
Fittings Utilizing Copper
Crimp Rings for PEX Tubing
Fittings to the ISA-S75.02
test method using the same
quadratic equation as the
Uponor ProPEX ttings to
determine pressure drop
versus ow data at precisely
8 ft./sec. Reference Table
C-1 for equivalent length
comparisons.
Table C-1: Equivalent length comparison of various PEX tting types
Fittings
Nominal
size (in.)
ASTM F1960 ASTM F1807 ASTM F2159
F1960 vs.
F1807
F1960 vs.
F2159
Uponor ProPEX
eq. length
Brass crimp
ring eq. length
Plastic crimp
ring eq. length
Tee run
½ 1 3.19 6.03 219.00% 503.00%
¾ 1.5 2.57 6.12 71.33% 308.00%
1 1.3 2.49 6.26 91.54% 381.54%
Tee branch
½ 6.3 9.05 15.34 43.65% 143.49%
¾ 15.6 10.16 17.04 -34.87% 9.23%
1 12.7 11.87 20.17 -6.54% 58.82%
Elbow
½ 10.4 9.11 13.53 -12.40% 30.10%
¾ 10.8 10.47 16.21 -3.06% 50.09%
1 11.5 10.14 17.05 -11.83% 48.26%
Coupling
½ 0.8 2.03 6.55 153.75% 718.75%
¾ 0.9 2.18 5.64 142.22% 526.67%
1 0.9 1.49 4.97 65.56% 452.22%