User Guide
Plumbing Design Assistance Manual l Appendix E – Expansion arm and loop calculations l 131
PEX with PEX-a Pipe Support, strut and strut clamps
has a thermal expansion rate of 0.08"/10°F ΔT/100 ft. (2.03mm/5.56°C ΔT/30.48m)
Thermal expansion
in underground
applications
For direct-burial applications,
mitigate the effects of thermal
expansion with a proper
installation that provides
adequate resistance to axial
stress. Per PPI TR-21 Thermal
Expansion and Contraction
in Plastics Piping Systems,
restrain a buried or concrete-
encased pipe from both
lateral and axial movement
with surrounding embedment
material. The magnitude of
the frictional restraining force
is dependent on the nature of
the soil and on installation and
operating conditions.
For example, the extent of
compaction near the pipe
can affect the quality of
contact between the pipe
and surrounding soil. The
anchoring or restraining effect
of surrounding soil on pipe
movement can be signicantly
augmented by external
pipe geometry. Tees, lateral
connections and changes in
direction all help to anchor a
pipe in the surrounding soil.
Appendix E:
Expansion arm and loop calculations
½" PEX pipe expansion arm
Delta
T (ΔT)
Run
(ft)
Delta L
(in)
Flexible arm
length (in)
L1
(in)
L2
(in)
PEX with PEX-a Pipe Support, strut and strut clamps
has a thermal expansion rate of 0.08"/10°F ΔT/100 ft. (2.03mm/5.56°C ΔT/30.48m).
10
50 0.04 1.90 0.38 0.76
60 0.048 2.08 0.42 0.83
70 0.056 2.24 0.45 0.90
80 0.064 2.40 0.48 0.96
90 0.072 2.55 0.51 1.02
100 0.08 2.68 0.54 1.07
20
50 0.08 2.68 0.54 1.07
60 0.096 2.94 0.59 1.18
70 0.112 3.17 0.63 1.27
80 0.128 3.39 0.68 1.36
90 0.144 3.60 0.72 1.44
100 0.16 3.79 0.76 1.52
30
50 0.12 3.29 0.66 1.31
60 0.144 3.60 0.72 1.44
70 0.168 3.89 0.78 1.56
80 0.192 4.16 0.83 1.66
90 0.216 4.41 0.88 1.76
100 0.24 4.65 0.93 1.86
40
50 0.16 3.79 0.76 1.52
60 0.192 4.16 0.83 1.66
70 0.224 4.49 0.90 1.80
80 0.256 4.80 0.96 1.92
90 0.288 5.09 1.02 2.04
100 0.32 5.37 1.07 2.15
½" PEX pipe expansion arm
Delta
T (ΔT)
Run
(ft)
Delta L
(in)
Flexible arm
length (in)
L1
(in)
L2
(in)
PEX with PEX-a Pipe Support, strut and strut clamps
has a thermal expansion rate of 0.08"/10°F ΔT/100 ft. (2.03mm/5.56°C ΔT/30.48m).
50
50 0.2 4.24 0.85 1.70
60 0.24 4.65 0.93 1.86
70 0.28 5.02 1.00 2.01
80 0.32 5.37 1.07 2.15
90 0.36 5.69 1.14 2.28
100 0.4 6.00 1.20 2.40
60
50 0.24 4.65 0.93 1.86
60 0.288 5.09 1.02 2.04
70 0.336 5.50 1.10 2.20
80 0.384 5.88 1.18 2.35
90 0.432 6.24 1.25 2.49
100 0.48 6.57 1.31 2.63
70
50 0.28 5.02 1.00 2.01
60 0.336 5.50 1.10 2.20
70 0.392 5.94 1.19 2.38
80 0.448 6.35 1.27 2.54
90 0.504 6.73 1.35 2.69
100 0.56 7.10 1.42 2.84
80
50 0.32 5.37 1.07 2.15
60 0.384 5.88 1.18 2.35
70 0.448 6.35 1.27 2.54
80 0.512 6.79 1.36 2.72
90 0.576 7.20 1.44 2.88
100 0.64 7.59 1.52 3.04
Table E-1: PEX pipe expansion arm calculations ½" to 3"