Chapter 17 — GEOTHERMAL ENERGY SYSTEMS AND AMBIENT TEMPERATURE LOOPS
1703.4 Underground Piping and Submerged Materi-
California Mechanical Code (Title 24, Part 4) · 2025 edition · updated 2026-09-10 · California
Italicized text is a California amendment to the model code, as printed in the official publication.
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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Ask AI about this code▸Contents — California Mechanical Code (Title 24, Part 4)
- Chapter 1 — GENERAL CODE PROVISIONS
- Chapter 2 — DEFINITIONS
- Chapter 3 — GENERAL REGULATIONS
- Chapter 4 — VENTILATION AIR
- Chapter 5 — EXHAUST SYSTEMS
- Chapter 6 — DUCT SYSTEMS
- Chapter 7 — COMBUSTION AIR
- Chapter 8 — CHIMNEYS AND VENTS
- Chapter 9 — INSTALLATION OF SPECIFIC APPLIANCES
- Chapter 10 — BOILERS AND PRESSURE VESSELS
- Chapter 11 — REFRIGERATION
- Chapter 12 — HYDRONICS
- Chapter 13 — FUEL GAS PIPING
- Chapter 14 — PROCESS PIPING
- Chapter 15 — SOLAR ENERGY SYSTEMS
- Chapter 16 — STATIONARY POWER PLANTS
▸Chapter 17 — GEOTHERMAL ENERGY SYSTEMS AND AMBIENT TEMPERATURE…
Overview- 1701.1 Applicability. Part I of this chapter shall apply to
- 1701.2 Construction Documents. The construction doc
- 1701.3 Site Survey. A site survey shall be conducted prior
- 1701.4 Used Materials. The installation of used pipe, fittings…
- 1701.5 Contact with Building Material. A ground source
- 1701.6 Strains and Stresses. Piping shall be installed so
- 1701.7 Flood Hazard. Piping located in a flood hazard area
- 1701.8 Pipe Support. Pipe shall be supported in accordance wit…
- 1701.9 Velocities. Ground source heat pump ground-loop
- 1701.10 Chemical Compatibility. Antifreeze and other
- 1701.11 Heat Transfer Fluid. The heat transfer fluid shall
- 1702.1 General. The potable water supply connected to a
- 1703.3 Fittings. For water-based systems, fittings for
- 1703.4 Underground Piping and Submerged Materi-
- 1703.1 Ground-Heat Exchanger Design. The groundheat exchanger …
- 1703.2 Piping and Tubing Materials Standards. For
- 1703.5 Indoor Piping. Indoor piping, fittings, and accessories…
- 1704.1 Heat Pump Distribution System. The heat pump
- 1704.2 Circulating Pumps. The circulating pump shall be
- 1705.1 Where Required. Shutoff valves shall be installed
- 1705.2 Heat Exchangers. Shutoff valves shall be installed
- 1705.3 Central Systems. Shutoff valves shall be installed
- 1705.4 Pressure Vessels. Shutoff valves shall be installed
- 1705.5 Pressure-Reducing Valves. Shutoff valves shall
- 1705.6 Equipment and Appliances. Shutoff valves shall
- 1705.7 Expansion Tanks. Shutoff valves shall be installed
- 1705.8 Reduced Pressure. A pressure relief valve shall
- 1706.1 General. Heat pumps shall be in compliance with
- 1706.2 Heat Exchangers. Heat exchangers used for heat
- 1706.3 Heat-Transfer Medium. The heat-transfer medium
- 1706.4 Insulation. The temperature of surfaces within
- 1707.1 Prior to Construction. Documents for permits
- 1707.2 Equipment, Accessories, Components, and
- 1707.3 Construction Documents. The construction documents for …
- 1707.4 Site Survey Requirements. The site survey shall
- 1707.5 Subsurface Investigation. A subsurface investigation sh…
- 1707.6 Subsurface Conditions. The water well logs and
- 1707.7 Ground-Heat Exchanger Installation Prac-
- 1707.13 Steel Nail Plates. Steel nail plates shall be
- 1707.14 Exterior Piping Protection. Exterior piping shall
- 1707.15 Heat Pump and Distribution System Instal-
- 1707.16 Pressurizing During Installation. Ground
- 1707.17 Horizontal Geothermal Piping - Materials
- 1707.18 Trenches, Excavation, and Backfill. Excavation
- 1707.8 Trenching, Excavation, and Backfill. Prior to
- 1707.9 Trenches, Tunneling, and Driving. Trenches shall
- 1707.10 Excavations and Open Trenches. Excavations
- 1707.11 Protection of Piping, Materials, and Struc-
- 1707.12 Sleeves. In exterior walls, annular space between
- 1708.1 General. The following requirements shall be verified p…
- 1708.2 Operation and Maintenance Manual. An operation and main…
- 1708.3 Labeling and Marking. Ground source heat pump
- 1708.4 Documentation. The ground source heat pump system as-bu…
- 1708.5 Maintenance. The periodic maintenance required,
- 1708.6 Records. The ground source heat pump system constructio…
- 1708.7 System Start-Up. System start-up shall be in accordance…
- 1708.8 Contaminants. Particulate contaminants shall be
- 1709.1 General. Decommissioning of geothermal systems
- 1710.1 Applicability. Part II of this chapter shall apply to
- 1710.2 Piping and Tubing. Piping and tubing for closedloop sys…
- 1710.3 Borehole Piping and Tubing. Borehole piping or
- 1710.4 Underground Fittings. Underground fittings for
- 1710.5 Verification. For closed-loop systems, the system
- 1710.6 Vertical Bores. Vertical bores shall be drilled to a
- 1711.1 Testing. Pressure-testing of the ground-heat
- 1711.2 Individual Loop Pressure Testing. Individual
- 1711.3 Field Pressure Testing – Final. The ground-heat
- 1711.4 Field Flow Testing – Final. Final field flow testing
- 1712.1 Applicability. Part III of this chapter shall apply to
- 1712.2 Test Wells. Test wells drilled to investigate subsurfac…
- 1712.3 Installation of Water Wells. Water supply,
- 1712.4 Setbacks. Open-loop ground-heat exchangers shall
- 1713.1 General. The installation and use of water wells
- 1713.2 Open-Loop Water Well Drilling Logs. The water
- 1713.3 Design Considerations. A groundwater heat
- 1713.4 Water Wells and Injection Wells. Water wells
- 1713.5 Testing and Sampling. Pumping tests and water
- 1713.6 Disinfection. Water wells shall be disinfected upon
- 1714.1 Pumping Test. Water supply wells and injection
- 1714.2 Retesting. Where sediment is present, the problem
- 1714.3 Variable Rate Pump Test. The operating conditions of th…
- 1714.4 Constant Rate Pump Test. The sustainable well
- 1714.5 Water Level Monitoring. Water levels shall be
- 1714.6 Injection Wells. Injection testing shall be performed
- 1714.7 Re-Injected Water. The water quality of re-injected
- 1715.1 General. The installation and use of Direct
- 1715.2 Applicability. Part IV of this chapter shall apply to
- 1715.3 DX Systems. Copper pipe and tubing installed for
- 1715.4 DX System Testing. For direct exchange (DX) systems, ea…
- 1715.5 Indoor Piping. For DX systems, joints shall be
- 1715.6 On Site Storage. For DX systems, copper piping
- 1715.7 System Start-Up. DX system start-up shall be in
- 1715.8 DX Piping. DX Piping should be installed in accordance …
- 1716.1 General. An Ambient Temperature Loop (ATL) distributed …
- 1716.2 Permitting. Permits required for the installation and
- 1716.3 Ambient Loop Temperature Range. The operating loop temp…
- 1716.4 Shutoff Valve. An automatic shutoff valve shall be
- 1716.5 Bypass. The ATL distributed energy system shall
- 1716.6 Metering. Where meters are required by the system
- 1717.1 Thermal Resources. The ambient temperature loop
- 1717.2 District Load Profiles. The district load profile of
- Chapter 18 — REFERENCED STANDARDS
- Appendix A — RESIDENTIAL PLAN EXAMINER REVIEW FORM FOR HVAC SY…
- Appendix B — PROCEDURES TO BE FOLLOWED TO PLACE GAS EQUIPMENT …
- Appendix C — INSTALLATION AND TESTING OF OIL (LIQUID) FUEL-FIR…
- Appendix D — FUEL SUPPLY: MANUFACTURED/MOBILE HOME PARKS AND R…
- Appendix E — SUSTAINABLE PRACTICES
- Appendix F — SIZING OF VENTING SYSTEMS AND OUTDOOR COMBUSTION …
- Appendix G — EXAMPLE CALCULATION OF OUTDOOR AIR RATE
- Appendix H — PROFESSIONAL QUALIFICATIONS
- Appendix I — INDOOR HORTICULTURAL FACILITIES
- Appendix J — CLEAN AIR DELIVERY