CPC · California Plumbing Code

Trenching, Excavation, Backfill & Sitework

This hub orients users to the CPC’s trenching, excavation and backfill rules (notably §314.0–314.4), why they matter, and key cross‑references to mechanical, building and utility requirements.

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Last reviewed: July 6, 2026

Overview

This part of the California Plumbing Code covers requirements for excavating and backfilling for plumbing work — where trenches are placed, tunneling and open-trench procedures, acceptable backfill materials and methods, and protection of piping during and after installation. Key CPC provisions include §314.0 through §314.4 on trenching, tunneling, open trenches and backfill and the related protections in §312.0 for piping and materials.

These rules exist to protect public safety, preserve nearby foundations and utilities, and ensure durable plumbing installations. Trenching for specialty systems (for example, ground‑heat exchangers) is also coordinated with the Mechanical Code (see §1707.8 / §1707.18), and site grading/backfill must interface with building‑code soil and fill rules such as CBC §1804.3; utility‑coordination and safety practices (call 811/USA, marking, compaction standards, warning tape) are commonly required by utilities and local authorities.

In this section

Code references

Grounded in the retrieved California Plumbing Code — click a citation to read the verbatim passage:

CPC § 1707.6 High relevance — show source text
1707.6 Subsurface Conditions . . . . . . . . . 350

1707.7 Ground-Heat Exchanger Installation Practices. . . . . . . . . . . 350

1707.8 Trenching, Excavation, and Backfill . . . . . . . . . . . . . . . . . . 351

1707.9 Trenches, Tunneling, and Driving . . . . . . . . . . . . . . . . . . 351

1707.10 Excavations and

Open Trenches. . . . . . . . . . . . . . . 351

1707.11 Protection of Piping, Materials, and Structures . . . . . . . 351

1707.12 Sleeves. . . . . . . . . . . . . . . . . . . . . 351

1707.13 Steel Nail Plates . . . . . . . . . . . . . . 351

1707.14 Exterior Piping Protection . . . . . . . 351

2025 CALIFORNIA MECHANICAL CODE

1707.15 Heat Pump and Distribution System Installation . . . . . . . . . . . . 351

1707.16 Pressurizing During Installation . . . . . . . . . . . . . . . . . . 351

1707.17 Horizontal Geothermal

Piping - Materials and Methods . . 351

1707.18 Trenches, Excavation,

and Backfill . . . . . . . . . . . . . . . . . . 351

1708.0 System Start-Up . . . . . . . . . . . . . . 352

1708.1 General. . . . . . . . . . . . . . . . . . . . . 352

1708.2 Operation and Maintenance Manual . . . . . . . . . . . . . . . . . . . . . 352

1708.3 Labeling and Marking . . . . . . . . . . 352

1708.4 Documentation . . . . . . . . . . . . . . . 352

1708.5 Maintenance . . . . . . . . . . . . . . . . . 352

1708.6 Records . . . . . . . . . . . . . . . . . . . . 352

1708.7 System Start-Up . . . . . . . . . . . . . . 352

1708.8 Contaminants . . . . . . . . . . . . . . . . 352

1709.0 Decommissioning and Abandonment . . . . . . . . . . . . . . . . 352

1709.1 General. . . . . . . . . . . . . . . . . . . . . 352

Part II Closed-Loop Systems . . . . . . . . 352

1710.0 General. . . . . . . . . . . . . . . . . . . . . 352

1710.1 Applicability. . . . . . . . . . . . . . . . . . 352

1710.2 Piping and Tubing. . . . . . . . . . . . . 352

1710.3 Borehole Piping and Tubing . . . . . 352
CPC § 1707.18 High relevance — show source text
1707.18 Trenches, Excavation, and Backfill. Excavation for horizontal piping shall comply with Section 1707.18.1 through Section 1707.18.8, Section 1707.8 through Section 1707.11, and in accordance with the requirements of the Authority Having Jurisdiction. Prior to any excavation, trenching, or drilling, all buried utilities including drainage, and irrigation systems shall be located and flagged by the appropriate utility and ground source heat pump system contractor representative.

1707.18.1 Trenches. Trenches for underground piping or tubing shall be excavated in accordance with the setback requirements in Section 1712.4. 1707.18.2 Buried Systems. Buried open-loop system piping, shall be installed not less than 3.3 feet (1006 mm) below the finished grade.

1707.18.3 Pipe Installation. Piping in horizontal trenches shall be embedded with not less than 6 inches (152 mm) of inert granular material above and below, or in accordance with the Authority Having Jurisdiction and project specifications.

Horizontal piping trenching shall be backfilled with approved material and shall be compacted. 1707.18.4 Separation. The horizontal piping shall be separated from fluid-based onsite service systems to prevent excessive short-circuiting heat transfer between such systems.

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(6) Vertical and horizontal ground-heat exchangers shall maintain the following setbacks:

(a) Ten feet (3048 mm) horizontally from a pressuretested sewer lateral into a building.

(b) Twenty feet (6096 mm) horizontally from a nonpressure tested sewer lateral into a building.

(c) Three feet (914 mm) horizontally from buried utilities such as electrical, gas, or water.

(d) Fifty feet (15 240 mm) from a water well.

(e) Fifty feet (15 240 mm) from a septic tank and 100 feet (30 480 mm) from a subsurface sewage leaching field.

(f) One hundred feet (30 480 mm) from a spring; or at distances specified by the Authority Having Jurisdiction.

(7) Wells and boreholes shall be sealed in accordance with the Authority Having Jurisdiction. Where grout is required, it shall be applied in a continuous operation from the bottom of the borehole by pumping through a tremie pipe.

1707.8 Trenching, Excavation, and Backfill. Prior to excavation, trenching, or drilling, buried utilities, drainage, water, and irrigation systems shall be located. Prior to excavation, trenching, or drilling, the contractor, and owner shall agree in writing to site restoration requirements and submit to the Authority Having Jurisdiction for approval. Prior to any excavation, trenching, or drilling, all buried utilities including drainage and irrigation systems shall be located and flagged by the appropriate utility and ground source heat pump system contractor representative.

1707.9 Trenches, Tunneling, and Driving. Trenches shall comply with Section 317.1. Tunneling and driving shall comply with Section 317.2.

CPC § 04-15 High relevance — show source text

. . . . . . . . . 063928

Table	1 Description of Items to be Furnished and Installed by Customer
Item	Description
1	Option 1: Meter Adapter, Cooper B-Line Cat. No. MARR20L45GRSD (160A) Use with Customer’s Panel Rated at 160A Continuous1, 2
1	Option 2: Meter Adapter, Ekstrom Industries No. 722B (175A). Specify Left, Right, or Bottom Hub
2	Combination Service Meter and Breaker Panel (rating as required)
3	Pull Termination Box, 8” x 12” x 4”, Rain-Tight, Circle A-W (Cooper B-Line) No. R-9007A or Equivalent (see Note 4M on Page 2)
4	Conduit, See Notes 4C and 4G on Page 1
5	Hub to Be Closed and Made Tamper Proof
6	Pull Termination Box, 12” x 26” x 6”, Rain-Tight, Circle A-W Catalog Number R-90008, or Equivalent (see Note 4K on Page 2)

1 Fifth jaw accessory, use Cooper B-Line Cat. No. 50365. 2 Reducer hub and gasket accessories for 2” conduit, use Cooper B-Line Cat. No. AW200 and 12750A.

061032 Page 2 of 4 Rev. #04: 04-15-11

UG-1: Services Greenbook Residential and Small Commercial Overhead to Underground Electric Service Conversion

Optional Removable by Customer To Be Removed by PG&E Meter Socket (see Figure 2 through Figure 7 on Pages 3 through 4) For Riser and Pull Box Detail (see Figure 2 through Figure 7 on Pages 3 through 4) For Gas and Water Sealing Requirements, see Documents 063927 and Document 063928 48” Min. 72” Max. Customer Shall Dig and Backfill Trench (see Note 4B on Page 1) Min. Bend Depth To PG&E Distribution System As required by	Col2	Col3
Customer Shall Dig and Backfill Trench (see Note 4B on Page 1) For Riser and Pull Box Detail (see Figure 2 through Figure 7 on Pages 3 through 4) Meter Socket (see Figure 2 through Figure 7 on Pages 3 through 4) To Be Removed by PG&E For Gas and Water Sealing Requirements, seeDocuments 063927 andDocument 063928 To PG&E Distribution System Optional Removable by Customer 48” Min. 72” Max. As required by Min. Bend Depth

Document 063927 and Document 063928

Figure 1 Typical Service Conversion

PG&E Service Termination Point

See Note 4K on Page 2

PG&E Service Termination Point (see Note 4L on Page 2)

CPC § 313.7 High relevance — show source text
313.7 Gas Piping. Gas piping shall be supported by metal straps or hooks at intervals not to exceed those shown in Table 1210.3.5.1.

313.8 [OSHPD 1, 2, 3, 4 & 5] Refer to Title 24, Part 2 of the California Building Code for seismic anchorage and bracing requirements and accommodations for building displace-

ments.

314.0 Trenching, Excavation, and Backfill.

314.1 Trenches. Trenches deeper than the footing of a building or structure, and paralleling the same, shall be located not less than 45 degrees (0.79 rad) from the bottom exterior edge of the footing, or as approved in accordance with Section 301.0.

314.2 Tunneling and Driving. Tunneling and driving shall be permitted to be done in yards, courts, or driveways of a building site. Where sufficient depth is available to permit, tunnels shall be permitted to be used between open-cut trenches.

Tunnels shall have a clear height of 2 feet (610 mm) above the pipe and shall be limited in length to one-half the depth of the trench, with a maximum length of 8 feet (2438 mm). Where pipes are driven, the drive pipe shall be not less than one size larger than the pipe to be laid.

314.3 Open Trenches. Excavations required to be made for the installation of a building drainage system or part thereof, within the walls of a building, shall be open trench work and shall be kept open until the piping has been inspected, tested, and accepted.

314.4 Excavations. Excavations shall be completely backfilled as soon after inspection as practicable. Precaution shall be taken to ensure compactness of backfill around piping without damage to such piping. Trenches shall be backfilled in thin layers to 12 inches (305 mm) above the top of the piping with clean earth, which shall not contain stones, boulders, cinder fill, frozen earth, construction debris, or other materials that will damage or break the piping or cause corrosive action. Mechanical devices such as bulldozers, graders, etc., shall be permitted to be then used to complete backfill to grade. Fill shall be properly compacted. Precautions shall be taken to ensure permanent stability for pipe laid in filled or made ground.

Underground thermoplastic pipe and fittings for sewers and other gravity flow applications shall be installed in accordance with this code and Section 314.4.1.

2025 CALIFORNIA PLUMBING CODE 53

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

GENERAL REGULATIONS
CPC § 3.2.2. High relevance — show source text
Additional information is available at www.pge.com/digsafely and about USA services at the USA North website http://www.usanorth.org. USA is a locating service for excavation only. Do not use USA for design purposes.

3.2.2. Establishing Underground Electric Service Responsibilities

Applicants are responsible for constructing, maintaining, and protecting specific portions of underground electric services during construction of their project. The following subsections describe those responsibilities and explain PG&E’s responsibilities during the construction process.

A. Applicants are responsible for obtaining all required permits and easements . This includes local building permits, environmental permits, encroachment permits, public utility easements, and any other permits and land rights that may be required based on the specific location of the trenching/excavation activities.

B. Applicants must ensure that the following construction activities, which may be required to establish underground service, are performed according to PG&E’s standards and specifications, PG&E-approved construction drawings and inspection requirements, and any other permit-specified requirements. This includes construction activities conducted on private property, in the franchise area, or in other rights-of-way areas. Construction activities include:
```
    - Trenching

    - Excavation

    - Backfill

    - Compaction

    - Underground conduit (conduit, bends, couplings, end bells, cable
```
protectors)
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    - Service riser conduit and connector (connects underground conduit
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to meter panel or termination enclosure)
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    - Substructures (boxes and pads)

    - Paving (cut, patch, and final repair)
```
C. Applicants must provide satisfactory termination facilities on or within the structures being served. (In this manual, see Sections 5, 6, 7, 8, 9, 10, and 11, as applicable, based on your project type, amperage, and voltage.) The locations for all transformers and meters, as well as the sizes, types, and quantities of conduit, are subject to PG&E’s specifications and approval.

2022 – 2023 3-2

Section 3, Electric Service: Underground

3.2.2. (continued)
CPC § 1707.8 High relevance — show source text
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(6) Vertical and horizontal ground-heat exchangers shall maintain the following setbacks:

(a) Ten feet (3048 mm) horizontally from a pressuretested sewer lateral into a building.

(b) Twenty feet (6096 mm) horizontally from a nonpressure tested sewer lateral into a building.

(c) Three feet (914 mm) horizontally from buried utilities such as electrical, gas, or water.

(d) Fifty feet (15 240 mm) from a water well.

(e) Fifty feet (15 240 mm) from a septic tank and 100 feet (30 480 mm) from a subsurface sewage leaching field.

(f) One hundred feet (30 480 mm) from a spring; or at distances specified by the Authority Having Jurisdiction.

(7) Wells and boreholes shall be sealed in accordance with the Authority Having Jurisdiction. Where grout is required, it shall be applied in a continuous operation from the bottom of the borehole by pumping through a tremie pipe.

1707.8 Trenching, Excavation, and Backfill. Prior to excavation, trenching, or drilling, buried utilities, drainage, water, and irrigation systems shall be located. Prior to excavation, trenching, or drilling, the contractor, and owner shall agree in writing to site restoration requirements and submit to the Authority Having Jurisdiction for approval. Prior to any excavation, trenching, or drilling, all buried utilities including drainage and irrigation systems shall be located and flagged by the appropriate utility and ground source heat pump system contractor representative.

1707.9 Trenches, Tunneling, and Driving. Trenches shall comply with Section 317.1. Tunneling and driving shall comply with Section 317.2.

1707.10 Excavations and Open Trenches. Excavations required to be made for the installation of piping or tubing shall be in accordance with Section 317.3. Piping or tubing shall be supported to maintain its alignment and prevent sagging. Piping in the ground shall be laid on a firm bed for its entire length; where other support is otherwise provided, it shall be approved in accordance with Section 302.0. Piping or tubing shall be backfilled after an inspection in accordance with Section 317.4.

1707.11 Protection of Piping, Materials, and Struc- tures. Piping and tubing passing under or through walls shall be protected from breakage in accordance with Section 316.1. Piping and tubing shall be installed in accordance with Section 316.2 to provide for expansion, contraction, and structural settlement. An electrically continuous corrosion-resistant tracer wire (not less than AWG 14) or tape shall be buried with the plastic pipe to facilitate locating. One end shall be brought aboveground at a building wall or riser.

1707.12 Sleeves. In exterior walls, annular space between sleeves and pipes shall be sealed and made watertight and shall not be subject to a load from building construction in accordance with Section 316.7 through Section 316.7.2.

2025 CALIFORNIA MECHANICAL CODE 351

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

GEOTHERMAL ENERGY SYSTEMS AND AMBIENT TEMPERATURE LOOPS

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California Plumbing Code High relevance — show source text
600
|87 300
|169 000
| |20
|1280
|2560
|4610
|7990
|12 100
|21 700
|60 000
|116 000
| |30
|1030
|2050
|3710
|6420
|9690
|17 400
|48 200
|93 200
| |40
|878
|1760
|3170
|5490
|8300
|14 900
|41 200
|79 700
| |50
|778
|1560
|2810
|4870
|7350
|13 200
|36 600
|70 700
| |60
|705
|1410
|2550
|4410
|6660
|12 000
|33 100
|64 000
| |70
|649
|1300
|2340
|4060
|6130
|11 000
|30 500
|58 900
| |80
|603
|1210
|2180
|3780
|5700
|10 200
|28 300
|54 800
| |90
|566
|1130
|2050
|3540
|5350
|9610
|26 600
|51 400
| |100
|535
|1070
|1930
|3350
|5050
|9080
|25 100
|48 600
| |125
|474
|949
|1710
|2970
|4480
|8050
|22 300
|43 000
| |150
|429
|860
|1550
|2690
|4060
|7290
|20 200
|39 000
| |175
|395
|791
|1430
|2470
|3730
|6710
|18 600
|35 900
| |200
|368
|736
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|2300
|3470
|6240
|17 300
|33 400
| |250
|326
|652
|1180
|2040
|3080
|5530
|15 300
|29 600
| |300
|295
|591
|1070
|1850
|2790
|5010
|13 900
|26 800
| |350
|272
|544
|981
|1700
|2570
|4610
|12 800
|24 700
| |400
|253
|506
|913
|1580
|2390
|4290
|11 900
|~~22 900~~
| |450
|237
|475
|856
|1480
|2240
|4020
|11 100
|21 500
| |500
|224
|448
|809
|1400
|2120
|3800
|10 500
|20 300
| |550
|213
|426
|768
|1330
|2010
|3610
|9990
|19
CPC § 312.0 High relevance — show source text
312.0 Protection of Piping, Materials, and Structures

314.0 Trenching, Excavation, and Backfill

701.3 Drainage Fittings

705.5.1.1 Butt Fusion Joints

705.5.1.2 Electro-Fusion Joints

705.5.1.3 Socket-Fusion Joints

723.0 Building Sewer Test

TABLE 1

CLEANOUTS (See Section 4.6.1)

The following standards from Tables 1701.1 and 1701.2 of the 2024 Uniform Plumbing Code apply.

Table 1701.1 Standards

ASTM D2239 Polyethylene (PE) Plastic Pipe (SIDRPR) Based on Controlled Inside Diameter

ASTM D2683 Socket-Type Polyethylene Fittings for Outside Diameter-Controlled Polyethylene Pipe and Tubing

ASTM D3261 Butt Heat Fusion Polyethylene (PE) Plastic Fittings for Polyethylene (PE) Plastic Pipe and Tubing

ASTM F714 Polyethylene (PE) Plastic Pipe (DRPR) Based on Outside Diameter

ASTM F894 Polyethylene (PE) Large Diameter Profile Wall Sewer and Drain Pipe

ASTM F1055 Electrofusion Type Polyethylene Fittings for Outside Diameter Controlled Polyethylene and Crosslinked Polyethylene (PEX) Pipe and Tubing

ASTM F2620 Heat Fusion Joining of Polyethylene Pipe and Fittings

Table 1701.2 Standards

ASTM D2657 Heat Fusion Joining of Polyolefin Pipe and Fittings

IAPMO PS 25 Metallic Fittings for Joining Polyethylene Pipe for Water Service and Yard Piping

Note: For SI units: 1 inch = 25 mm

2025 CALIFORNIA PLUMBING CODE 453

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

454 2025 CALIFORNIA PLUMBING CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

"The information contained in this appendix is not part of this American National Standard (ANS) and has not been processed in accordance with ANSI's requirements for an ANS. As such, this appendix may contain material that has not been subjected to public review or a consensus process. In addition, it does not contain requirements necessary for conformance to the standard."

The following IAPMO Installation Standard is included here for the convenience of the users of the Uniform Plumbing Code. It is not considered as a part of the Uniform Plumbing Code unless formally adopted as such. This Installation Standard is an independent, stand-alone document published by the International Association of Plumbing and Mechanical Officials and is printed herein by the expressed written permission of IAPMO.

INSTALLATION STANDARD FOR PEX TUBING SYSTEMS

FOR HOT- AND COLD-WATER DISTRIBUTION

IAPMO IS 31-2022

The provisions contained in this appendix are not mandatory unless specifically adopted by a state agency, or referenced in the adopting ordinance.

1 Scope

1.1 General

1.1.1 This Standard specifies requirements for the installation of SDR 9 CTS crosslinked polyethylene (PEX) tubing and fittings, including cold-expansion, crimp, press, and mechanical compression fittings, intended for hot- and cold-water distribution systems within buildings.

1.1.2 This Standards applies to
CPC § 313.6 High relevance — show source text
Table 313.6 Hanger Rod Sizes . . . . . . . . . . . . .53

313.7 Gas Piping . . . . . . . . . . . . . . . . . . .53

314.0 Trenching, Excavation, and Backfill . . . . . . . . . . . . . . . . . . . . . .53

314.1 Trenches . . . . . . . . . . . . . . . . . . . . .53

314.2 Tunneling and Driving . . . . . . . . . .53

314.3 Open Trenches . . . . . . . . . . . . . . . .53

314.4 Excavations . . . . . . . . . . . . . . . . . .53

315.0 Joints and Connections . . . . . . . . .54

315.1 Unions . . . . . . . . . . . . . . . . . . . . . .54

315.2 Prohibited Joints and

Connections . . . . . . . . . . . . . . . . . .54

316.0 Increasers and Reducers . . . . . . . .54

316.1 General . . . . . . . . . . . . . . . . . . . . . .54

317.0 Food-Handling Establishments . . . .54

317.1 General . . . . . . . . . . . . . . . . . . . . . .54

318.0 Test Gauges . . . . . . . . . . . . . . . . . .54

318.1 General . . . . . . . . . . . . . . . . . . . . . .54

318.2 Pressure Tests (10 psi or less) . . .54

318.3 Pressure Tests (greater than 10 psi to 100 psi) . . . . . . . . . . . . . .54

318.4 Pressure Tests (exceeding 100 psi) . . . . . . . . . . . . . . . . . . . . . .54

318.5 Pressure Range . . . . . . . . . . . . . . .54

319.0 Medical Gas and Vacuum

Systems . . . . . . . . . . . . . . . . . . . . .54

319.1 General . . . . . . . . . . . . . . . . . . . . . .54

320.0 Rehabilitation of Piping Systems . .54

320.1 General . . . . . . . . . . . . . . . . . . . . . .54

321.0 Essential Plumbing Provisions . . . .54

322.0 Psychiatric Services . . . . . . . . . . . .54

323.0 Plumbing Equipment Schedules . . .55

Table 313.3 Hangers and Supports . . . . . . . . . .55

CHAPTER 4 PLUMBING FIXTURES

AND FIXTURE FITTINGS . . . . . . .57

401.0 General . . . . . . . . . . . . . . . . . . . . . .59

401.1 Applicability . . . . . . . . . . . . . . . . . . .59
CPC § 312.2 High relevance — show source text
312.2 Installation . . . . . . . . . . . . . . . . . . .52

312.3 Building Sewer and Drainage Piping . . . . . . . . . . . . . . . . . . . . . . .52

312.4 Corrosion, Erosion, and Mechanical Damage . . . . . . . . . . . .52

312.5 Protectively Coated Pipe . . . . . . . .52

312.6 Freezing Protection . . . . . . . . . . . .52

312.7 Fire-Resistant Construction . . . . . .52

312.8 Waterproofing of Openings . . . . . .52

312.9 Steel Nail Plates . . . . . . . . . . . . . . .52

312.10 Sleeves . . . . . . . . . . . . . . . . . . . . . .52

312.11 Structural Members . . . . . . . . . . . .53

312.12 Rodentproofing . . . . . . . . . . . . . . . .53

313.0 Hangers, Supports, and Anchors . . .53

313.1 General . . . . . . . . . . . . . . . . . . . . . .53

313.2 Material . . . . . . . . . . . . . . . . . . . . . .53

313.3 Suspended Piping . . . . . . . . . . . . .53

313.4 Alignment . . . . . . . . . . . . . . . . . . . .53

313.5 Underground Installation . . . . . . . .53

313.6 Hanger Rod Sizes . . . . . . . . . . . . .53

Table 313.6 Hanger Rod Sizes . . . . . . . . . . . . .53

313.7 Gas Piping . . . . . . . . . . . . . . . . . . .53

314.0 Trenching, Excavation, and Backfill . . . . . . . . . . . . . . . . . . . . . .53

314.1 Trenches . . . . . . . . . . . . . . . . . . . . .53

314.2 Tunneling and Driving . . . . . . . . . .53

314.3 Open Trenches . . . . . . . . . . . . . . . .53

314.4 Excavations . . . . . . . . . . . . . . . . . .53

315.0 Joints and Connections . . . . . . . . .54

315.1 Unions . . . . . . . . . . . . . . . . . . . . . .54

315.2 Prohibited Joints and

Connections . . . . . . . . . . . . . . . . . .54

316.0 Increasers and Reducers . . . . . . . .54

316.1 General . . . . . . . . . . . . . . . . . . . . . .54

317.0 Food-Handling Establishments . . . .54

317.1 General . . . . . . . . . . . . . . . . . . . . . .54

318.0 Test Gauges . . . . . . . . . . . . . . . . . .54
CPC § 1705.3 High relevance — show source text
1705.3 Central Systems . . . . . . . . . . . . . . 349

1705.4 Pressure Vessels . . . . . . . . . . . . . 349

1705.5 Pressure-Reducing Valves . . . . . . 349

1705.6 Equipment and Appliances. . . . . . 349

1705.7 Expansion Tanks . . . . . . . . . . . . . 349

1705.8 Reduced Pressure . . . . . . . . . . . . 350

1706.0 Specific System Components Design . . . . . . . . . . . . . . . . . . . . . 350

1706.1 General. . . . . . . . . . . . . . . . . . . . . 350

Table 1706.1 Heat Pumps . . . . . . . . . . . . . . . . . 350

1706.2 Heat Exchangers . . . . . . . . . . . . . 350

1706.3 Heat-Transfer Medium . . . . . . . . . 350

1706.4 Insulation . . . . . . . . . . . . . . . . . . . 350

1707.0 Installation Practices. . . . . . . . . . . 350

1707.1 Prior to Construction. . . . . . . . . . . 350

1707.2 Equipment, Accessories, Components, and Materials . . . . . 350

1707.3 Construction Documents . . . . . . . 350

1707.4 Site Survey Requirements . . . . . . 350

1707.5 Subsurface Investigation . . . . . . . 350

1707.6 Subsurface Conditions . . . . . . . . . 350

1707.7 Ground-Heat Exchanger Installation Practices. . . . . . . . . . . 350

1707.8 Trenching, Excavation, and Backfill . . . . . . . . . . . . . . . . . . 351

1707.9 Trenches, Tunneling, and Driving . . . . . . . . . . . . . . . . . . 351

1707.10 Excavations and

Open Trenches. . . . . . . . . . . . . . . 351

1707.11 Protection of Piping, Materials, and Structures . . . . . . . 351

1707.12 Sleeves. . . . . . . . . . . . . . . . . . . . . 351

1707.13 Steel Nail Plates . . . . . . . . . . . . . . 351

1707.14 Exterior Piping Protection . . . . . . . 351

2025 CALIFORNIA MECHANICAL CODE

1707.15 Heat Pump and Distribution System Installation . . . . . . . . . . . . 351

1707.16 Pressurizing During Installation . . . . . . . . . . . . . . . . . . 351

1707.17 Horizontal Geothermal

Piping - Materials and Methods . . 351

1707.18 Trenches, Excavation,

and Backfill . . . . . . . . . . . . . . . . . . 351

1708.0 System Start-Up . . . . . . . . . . . . . . 352
CPC § 309.0 Medium relevance — show source text
2025 CALIFORNIA PLUMBING CODE 469

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

IS 33

Uniform Plumbing Code References for Ductile Iron and PVC Pressure Building Supply and Exterior Cold-Water Piping

The following sections of the 2024 Uniform Plumbing Code apply to ductile iron and PVC pressure building supply and exterior cold-water piping.

Chapter 3 General Regulations

309.0 Workmanship

312.0 Protection of Piping, Materials, and Struc tures

313.0 Hangers, Supports, and Anchors

314.0 Trenching, Excavation, and Backfill

Chapter 6 Water Supply and Distribution

604.0 Materials (water piping)

Table 604.1 Materials for Building Supply and Water Distribution Piping and Fittings

605.4 Ductile Iron Pipe and Joints

605.12 PVC Plastic Pipe and Joints

605.16.2 Plastic Pipe to Other Materials

609.0 Installation, Testing, Unions, and Location

Abbreviations

IAPMO International Association of Plumbing and Mechanical Officials

UPC Uniform Plumbing Code published by IAPMO

AWWA American Water Works Association

CSA Canadian Standards Association

Applicable Standards.

ASME B16.4 Gray Iron Threaded Fittings Classes 125 and 250

ASTM D1785 Poly (Vinyl Chloride) (PVC) Plastic Pipe, Schedules 40, 80, and 120

ASTM D2241 Poly (Vinyl Chloride) (PVC) Pressure-Rated Pipe (SDR Series)

ASTM D2466 Poly (Vinyl Chloride) (PVC) Plastic Pipe Fittings, Schedule 40

ASTM D2467 Poly (Vinyl Chloride) (PVC) Plastic Pipe Fittings, Schedule 80

ASTM F1970 Special Engineered Fittings, Appurtenances or Valves for use in Poly (Vinyl Chloride) (PVC) or Chlorinated Poly (Vinyl Chloride) (CPVC) Systems

AWWA C110 Ductile Iron and Gray-Iron Fittings

AWWA C111 Rubber-Gasket Joints for Ductile-Iron Pressure Pipe and Fittings

AWWA C151 Ductile-Iron Pipe, Centrifugally Cast

AWWA C153 Ductile-Iron Compact Fitting

AWWA C900 Polyvinyl Chloride (PVC) Pressure Pipe and Fabricated Fittings, 4 in. through 12 in. (100 mm through 300 mm)

AWWA C904 Crosslinked Polyethylene (PEX) Pressure Tubing, ½ in. through 3 In. (13 mm through 76 mm), for Water Service

AWWA C907 Injection-Molded Polyvinyl Chloride (PVC) Pressure Fittings, 4 In, through 12 in (100 mm through 300 mm) for Water, Wastewater and Reclaimed Water Service

IAPMO/

ANSI UPC-1 Uniform Plumbing Code

470 2025 CALIFORNIA PLUMBING CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

Frequently asked questions

Do I have to locate utilities before excavating?

Yes — excavators must identify and have buried facilities located/marked (call 811/USA where applicable) before digging; utilities and local agencies also impose marking, permitting, and safety requirements.

What does the CPC require for backfilling around plumbing piping?

The CPC requires backfilling as soon as practicable after inspection, with clean earth placed in thin lifts to at least 12 inches above the pipe, free of stones, debris or frozen material, and compacted to prevent settlement or damage to the piping.

Are there special trenching rules for geothermal or other mechanical ground loops?

Yes — trenching and backfill for ground‑heat exchangers and horizontal piping reference the Mechanical Code installation rules (for example §1707.8 and §1707.18) which specify setbacks, bedding, minimum depths and separation from other systems.

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Related in the CPC

Scope & Minimum Standards (Chapter 3)

Workmanship, Hangers & Protection

Identification, Referenced Standards & How They Apply

General Regulations

California Plumbing Code