Loop Field Materials and Components
What the exam tests
This domain tests recognition and correct application of loop-field materials: HDPE pipe, fittings, U-bends, spacers, grout, headers, vaults, pumps, and antifreeze. Expect questions on dimension ratio, pressure rating, temperature derating, and component compatibility.
Core rules
- Ground-loop pipe is typically HDPE PE3408 or PE3608. DR11 is common; lower DR means thicker wall and higher pressure rating.
- Pressure rating falls as temperature rises; do not use the 73°F rating for a hot-loop or severe condition without derating.
- Use fusion-compatible fittings and materials; do not mix PVC, copper, or dissimilar pipe in buried joints.
- U-bends, spacers, and centralizers keep pipes separated and improve grout coverage.
- Headers, flow centers, expansion tanks, and pumps must match flow and pressure requirements.
Worked example
A 2-in DR11 PE3608 pipe is rated 200 psi at 73°F. The design operating pressure is 60 psi, so the minimum hydrostatic test is 1.5 × 60 = 90 psi, but the common minimum is 100 psi. Use 100 psi, provided it does not exceed the pipe rating at test temperature. A DR17 pipe has a lower rating and may not be acceptable for the same test.
Traps
Mixing DRs in one buried run; assuming all HDPE has the same rating; using potable-water fittings; ignoring temperature derating; selecting a pump by horsepower instead of flow at head.