Chapter 17 — GEOTHERMAL ENERGY SYSTEMS AND AMBIENT TEMPERATURE LOOPS
1703.4 Underground Piping and Submerged Materi-als — 2025 California Mechanical Code
California Mechanical Code (Title 24, Part 4) · 2025 edition · updated 2026-09-25 · California
CBSC: official editions, supplements and errata
Italicized text is a California amendment to the model code, as printed in the official publication.
Cite as: 2025 California Mechanical Code (Title 24, Part 4) § 1703.4 · Effective January 1, 2026 · Official source: Building Standards Commission
als. Underground and submerged piping for a ground-heat exchanger shall be polyethylene (PE) pipe or tubing in accordance with Section 1703.4.1 and Section 1703.4.1.1, or crosslinked polyethylene (PEX) pipe or tubing in accordance with Section 1703.4.2 and Section 1703.4.2.1.
1703.4.1 Polyethylene (PE). Polyethylene pipe or tubing shall be manufactured in accordance with the standards listed in Table 1703.2. Pipe or tubing shall have a minimum wall thickness equal to SDR-11 and shall have a minimum pressure rating of not less than 160 psi (1103 kPa) at 73°F (23°C).
Polyethylene pipe and tubing shall be manufactured from a PE compound that has a pipe material designation code of PE 3608, PE 3708, PE 3710, PE 4608, PE 4708, or PE 4710 as defined in the applicable standards referenced in Table 1703.2, with a cell classification in accordance with ASTM D3350 appropriate for the material designation code, and a color and ultraviolet stabilizer code of C or E. Code E compounds shall be stabilized against deterioration from unprotected exposure to ultraviolet rays for not less than 3 years in accordance with the test criteria specified in ASTM D2513.
1703.4.1.1 Joining Methods for Polyethylene Pipe or Tubing. Joints between high density polyethylene (HDPE) plastic pipe or tubing and fittings shall be installed in accordance with the manufac
TABLE 1701.11.1
WATER QUALITY [1]
WATER QUALITY TABLE 1703.3
GROUND SOURCE LOOP PIPE FITTINGS
| PARAMETER | ACCEPTABLE RANGE |
|---|---|
Ammonium |
< 2 ppm |
Chlorides2 |
< 125 ppm |
(Free CO2)3 |
< 50 ppm |
pH |
7.0 – 8.5 |
Sulphates |
< 125 ppm |
TDS |
10 – 1000 ppm |
Total Hardness |
< 150 ppm |
Notes: 1 Where chemical additives are used, the acceptable ranges provided shall be in accordance with the equipment manufacturer’s specifications, or this table, whichever is more stringent. 2 The provided acceptable range for chlorides is dependent upon the system heat exchanger and piping materials. See the manufacturer’s specifications for equipment and materials used. 3 The limit provided pertains to makeup water.
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backflow prevention device. The connection of a discharge line to the sanitary or storm sewer system, or private sewage disposal system, shall be in accordance with the plumbing code or in accordance with the Authority Having Jurisdiction.
TABLE 1701.11.1
WATER QUALITY [1]
Notes: 1 Where chemical additives are used, the acceptable ranges provided shall be in accordance with the equipment manufacturer’s specifications, or this table, whichever is more stringent. 2 The provided acceptable range for chlorides is dependent upon the system heat exchanger and piping materials. See the manufacturer’s specifications for equipment and materials used. 3 The limit provided pertains to makeup water.
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