PEX Installation Manual

IM-PF 724596 0416
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11.1 Below grade and service line
ViegaPEX Ultra and FostaPEX tubing may both be
used underground and for water service piping. When
running lines underground, it is important to provide a
stable, continuous trench base to support the tubing.
Always allow sufcient slack when tubing is laid in
trenches. Snake the tubing slightly side-to-side to
provide for contraction due to temperature change.
Do not use blocking to support tubing. PEX tubing
can be damaged by contact with sharp objects.
Ensure that trench bottom and ll do not contain sharp
rocks or other items. In good soil conditions tubing
may be placed directly on trench bottom. In poor soil
conditions (rocky, loose, etc.) the trench should be
excavated at least six inches below the tubing level and
backlled with appropriate material to provide a stable
base (coarse sand, pea gravel or similar).
Backll material must be free of large rocks, glass or
other sharp objects. Provide sufcient coverage over
tubing so that expected trafc loads will not deform
tubing (consult local codes). Compact this material to at
least 6" above the tube.
Trench in poor soil
Trench in good soil
Do not install ViegaPEX Ultra tubing where soil is or
may become contaminated with solvents, fuels or
similar chemicals. Do not install tubing above or below
septic tanks, leach elds, pits or cesspools.
Always follow local codes when installing ViegaPEX
Ultra tubing. Consult standards such as ASTM D2774:
Standard Recommended Practice for Underground
Installation of Thermoplastic Pressure Piping for further
information.
11 Water Service Installation
Allow sufficient slack when tubing is laid
in trench