CPC · California Plumbing Code

What are trenching, excavation and backfill requirements for plumbing installations?

Q: Do I have to leave trenches open for inspection?

Yes. Open trenches for in‑building drainage work must be kept open until the piping has been inspected, tested and accepted — § 314.3 .

Q: What material can I use to backfill around pipe?

Use clean earth free of stones, boulders, cinders, frozen earth, construction debris or other damaging/corrosive materials; backfill in thin layers to 12 inches above pipe top and compact — § 314.4 .

In plain terms: when you dig for plumbing, keep trenches a safe distance from footings (45° setback), keep trenches open until plumbing is inspected, limit tunnels to the code’s height/length rules, and backfill with clean earth in thin compacted layers at least 12 inches above the pipe — see CPC **§ 314.1–§ 314.4** for the specifics .

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The California Plumbing Code requires that trenches, tunnels and excavations for plumbing be located, sized and kept open or backfilled in ways that protect footings, piping and public safety. Key dimensional rules include a minimum setback relative to a building footing, minimum clearances and length limits for tunnels, and backfill material/compaction requirements (see § 314.1, § 314.2, § 314.3, § 314.4) . All work must be inspected before final backfill where the code requires the trench to remain open for inspection .

The single most important practical rule: keep open trenches open until the piping is inspected and tested, and backfill with clean, non‑damaging earth in thin layers to at least 12 inches above the top of the pipe, compacted to provide permanent stability (§ 314.3–314.4) .

Requirements in detail

1) Trenches adjacent to buildings and footings

If a trench is deeper than the footing of a building or structure and runs parallel to it, it must be located not less than 45 degrees from the bottom exterior edge of the footing (that is, the trench must be horizontally far enough away that a 45° line from the footing bottom clears the trench) — § 314.1 .
Practical consequence: the required horizontal setback grows as the difference between trench depth and footing bottom increases (see worked example below) — § 314.1 .

2) Tunneling / driven pipe

Tunnels (boring between open-cut trenches) are allowed in yards, courts or driveways where depth permits. Tunnels must have a clear height of 2 ft (610 mm) above the pipe. The tunnel length is limited to one‑half the trench depth, with an absolute maximum length of 8 ft (2438 mm). Where pipe is driven, the drive pipe must be not less than one size larger than the pipe to be laid — § 314.2 .

3) Open trenches and inspection

Excavations for building drainage within walls of a building (open trench work) must be kept open until the piping has been inspected, tested and accepted — § 314.3 .

4) Backfill material, layering and compaction

Excavations shall be backfilled as soon after inspection as practicable; take care to ensure compactness around piping without damaging the piping — § 314.4 .
Trenches shall be backfilled in thin layers to 12 inches (305 mm) above the top of the piping with clean earth that 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 — § 314.4 .
After the initial thin-layer backfill above the pipe, mechanical devices (bulldozers, graders, etc.) may be used to complete the backfill to grade; fill shall be properly compacted and precautions taken to ensure permanent stability when pipe is laid in filled or made ground — § 314.4 .
The Code separately identifies installation-specific requirements for underground thermoplastic pipe in relation to excavation/backfill (see reference to § 314.4.1 in the code text) — text of § 314.4.1 was referenced but not included in the retrieved file preview; see note below about unavailable text .

Quick reference table — decision‑relevant dimensions & values

Requirement / dimension	Value or rule	Code Reference
Minimum setback from footing (angle)	45° from bottom exterior edge of footing	§ 314.1
Tunnel clear height above pipe	2 ft (610 mm)	§ 314.2
Tunnel maximum length	One‑half trench depth, but no more than 8 ft (2438 mm)	§ 314.2
Drive pipe size when driving pipe	Drive pipe ≥ one size larger than pipe to be laid	§ 314.2
Keep open trenches open until	Inspected, tested and accepted	§ 314.3
Backfill first lift above pipe	Thin layers to 12 in (305 mm) above top of pipe, clean earth only	§ 314.4
Prohibited backfill contents	Stones, boulders, cinder fill, frozen earth, construction debris, corrosive materials	§ 314.4
Mechanical completion of backfill	Allowed after initial thin-layer backfill; fill must be properly compacted	§ 314.4

Exceptions & special cases

The Code text explicitly refers to additional, specific provisions for underground thermoplastic pipe (a follow-up subsection § 314.4.1). That subsection was referenced in the retrieved material but its full text was not included in the files I was given; therefore I cannot quote or summarize the exact thermoplastic‑specific requirements from § 314.4.1 here — consult § 314.4.1 in the full CPC for those details .
Where site conditions, local jurisdiction requirements, or other code chapters apply (for example, protection of piping, seismic restraint, or underground installation practices), follow those requirements in addition to § 314.0 series (see Related Provisions below) .

Common mistakes

Backfilling before inspection: closing trenches before the required inspection/testing is the most frequent error — remember § 314.3 requires trenches for certain in‑building drainage work to remain open until accepted .
Using inappropriate backfill: placing rocks, cinders, frozen earth or construction debris directly around pipe — prohibited by § 314.4 and a common cause of pipe damage and leaks .
Improper compaction sequence: using heavy equipment directly over freshly laid pipe before the pipe has a protective initial layer and been inspected; the code requires initial thin-layer backfill to at least 12 inches above the pipe before heavy equipment may finish the fill — § 314.4 .
Misreading the 45° setback: the rule in § 314.1 is geometric; installers sometimes confuse footing top or excavation edge with the bottom exterior edge of the footing — the reference point is the bottom exterior edge of the footing, and the required line is 45° from that point .

Worked example — concrete scenario

Scenario: you are installing a sewer line in a trench that runs parallel to an existing building footing. The footing bottom is at 2 ft below finished grade. Your trench bottom will be at 8 ft below finished grade.

Step 1 — setback from footing (apply § 314.1):

Trench depth below footing bottom = 8 ft − 2 ft = 6 ft.
Required horizontal offset = tan(45°) × (trench depth difference) = 1 × 6 ft = 6 ft.
So the trench must be located at least 6 ft horizontally from the bottom exterior edge of the footing (i.e., the 45° line clearance) — § 314.1 .

Step 2 — tunneling (if you consider tunneling between open cuts) (apply § 314.2):

Maximum tunnel length = one‑half trench depth = 0.5 × 8 ft = 4 ft (which is less than the absolute maximum of 8 ft).
Minimum clear height inside tunnel above the pipe = 2 ft (610 mm) — § 314.2 .

Step 3 — backfill after inspection (apply § 314.3–314.4):

Keep trench open until piping is inspected, tested and accepted — § 314.3 .
After acceptance, backfill in thin layers up to 12 in (305 mm) above the top of the pipe using clean earth (no rocks, cinders, frozen earth, debris), compact each layer to achieve proper density, then mechanical equipment may complete backfill to grade — § 314.4 .

Related provisions (CPC)

§ 312.0 — Protection of piping, materials and structures (see related protection requirements) .
§ 313.5 — Underground installation (piping in the ground shall be laid on a firm bed for its entire length) .
§ 314.1 — Trenches (setback rule) — primary controlling subsection here .
§ 314.2 — Tunneling and driving (tunnel height and length limits) .
§ 314.3 — Open trenches (inspection requirement) .
§ 314.4 — Excavations and backfill (materials, layering, compaction) .
§ 314.4.1 — Thermoplastic pipe specifics (referenced by § 314.4; full text not present in retrieved preview — consult the full CPC document) .

(For related mechanical/geothermal installation guidance, see the California Mechanical Code trenching sections such as § 1707.8–§ 1707.11, which parallel the plumbing provisions for certain buried piping installations) .

Code references

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

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 § 609.12.3 High relevance — show source text
Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .609.12.3

Joints and connections . . .(see Joints and connections) Location (OSHPD) . . . . . . . . . . . . . . . . . . . . . . . .310.11 Medical gas, material . . . . . . . . . . . . . . . . . . . . . .1318.0 Plumbing vent, material . . . . . . . . . . .Table 701.2, 903.0 Protection of . . . . . . . . . . . . . . . . . . . . . . . .312.0, 718.3,

1210.1.3 – 1210.1.5

Rehabilitation of . . . . . . . . . . . . . . . . . . . . . . . . . .320.0

Separation in trenches . . . . . . . . . . . . . . . . . . .1505.11 Sprinkler system, lawn . . . . . . . . . . Table 610.3, 612.1, Table A 103.1, A 103.2, M 102.5 Storm drainage, materials . . . . . . . . . .1101.4 – 1101.4.6 Trenching, excavation,

and backfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314.0

Underground . . . . . . . . . . . . . . . . . . . .314.4.1, 1210.1.6 Water supply, material . . . . . . . . . . . .604.0, Table 604.1 PITS, SEEPAGE . . . . . . . . . . . . . . . . . .221.0, 714.3, 716.1, 722.2 – 722.4, Appendix H PLUGS, CAPS, CLEANOUT . . . . . . . . . . . . . . .707.1, 707.2

PLUMBING

Additions, alterations,

renovations or repairs . . . . . . . . . . . . . . . . . . . .102.4 Appliances . . . . . . . . . . . . . .218.0, 304.1, 310.5, 313.1, 417.2, 603.4.6, 606.5, Table 610.3,

Table 702.1, 801.7, 803.3, 806.1,

807.0, 808.1, Table A 103.1, L 302.2

Appurtenances . . . . . . . . .218.0, 304.1, 313.1, 603.4.6, Table 610.3, Table 702.1, 814.2.1,

1505.9.2, 1505.11, 1506.10.3,

1602.9, Table A 103.1, L 501.2

Connected to sewer or

private disposal systems . . . . . .304.1, 713.1, L 302.2
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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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 § 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 § 8.8 High relevance — show source text
details: see Note 8 figure.|8.8 tons|3 hrs
32
min|||7|1, 3, 14|31/2| |B-11-RC-5|11″|24″ wide × 11″ deep reinforced concrete “T”
beam (4250 psi); details: see Note 9 figure.|8.8 tons|3 hrs
3 min|||7|1, 3, 14|3| |B-11-RC-6|11″|Concrete flange: 4″ deep × 2' wide (4895 psi)
concrete; concrete beam: 7″ deep × 61/2″
wide; “I” beam reinforcement; 10″ × 41/2″ ×
25 lbs R.S.J.; 1″ cover on flanges; flange rein-
forcement:3/8″ diameter bars at 6″ pitch
parallel to “T”; 1/4″ diameter bars perpendic-
ular to “T”; beam reinforcement: 4″ × 6″ No.
13 SWG wire mesh; span: 11' restrained;
details: see Note 10 figure.|10 tons|6 hrs|||7|1, 4|6| |B-11-RC-7|11″|Concrete flange: 6″ deep × 1' 61/2″ wide (3525
psi) concrete; concrete beam: 5″ deep × 8″
wide precast concrete blocks 83/4″ long; “I”
beam reinforcement; 7″ × 4″ × 16 lbs R.S.J.;
2″ cover on bottom; 11/2″ cover on top;
flange reinforcement: two rows1/2″ diameter
rods parallel to “T”; beam reinforcement:1/8″
wire mesh perpendicular to “T”; span: 1′3″
simply supported; details: see Note 11
figure.|3.9 tons|4 hrs|||7|1, 2|4| |B-11-RC-8|11″|Concrete flange: 4″ deep × 2' wide (3525 psi)
concrete; concrete beam 7″ deep × 41/2″
wide (scaled from drawing); “I” beam rein-
forcement; 10″ × 41/2″ × 25 lbs R.S.J.; no
concrete cover on bottom; flange reinforce-
ment:3/8″ diameter bars at 6 pitch parallel to
“T”;1/4″ diameter bars perpendicular to “T”;
span: 11′ restricted; details: see Note 12
figure.|10 tons|4 hrs|||7|1, 2|4| |B-11-RC-9|111/2″|24″ wide × 111/2″ deep reinforced concrete
“T” beam (4390 psi); details: see Note 13
figure.|8.8 tons|3 hrs
24
min|||7|1, 3|31/3|

For SI: 1 inch = 25.4 mm, 1 foot = 305 mm, 1 pound = 0.004448 kN, 1 pound per square inch = 0.00689 MPa, 1 ton = 8.896 kN.

Notes:
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 § 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 § 2.25 High relevance — show source text
00|2.25|0.70|DR|3.70|1.05|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|33 mil cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|16|3.85|1.45|DR|DR|3.40|DR|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|33 mil cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|24|3.40|DR|DR|DR|2.70|DR|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#8 Screw|Steel thick-
ness plus 3
threads|12|3.00|1.80|DR|DR|3.00|0.65|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#8 Screw|Steel thick-
ness plus 3
threads|16|3.00|1.00|DR|DR|2.85|DR|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#8 Screw|Steel thick-
ness plus 3
threads|24|2.85|DR|DR|DR|2.20|DR|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|12|4.00|3.85|2.80|1.80|4.00|3.05|1.50|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|16|4.00|3.30|1.95|0.60|4.00|2.25|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|24|4.00|2.25|DR|DR|4.00|0.65|DR|DR| |For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa, 1 pound per square inch = 0.00689 MPa.
DR = Design Required, o.c. = on center.
a. Wood furring shall be spruce-pine-fir or any softwood species with a specific gravity of 0.42 or greater.
CPC § 3.2.2. Medium 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)
```
    - Service riser conduit and connector (connects underground conduit
```
to meter panel or termination enclosure)
```
    - 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 § 309.0 Medium relevance — show source text
2025 CALIFORNIA PLUMBING CODE 469

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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.
CPC § 701.2 Medium relevance — show source text
PIPING

ABS and PVC, residential . . . . . . . .701.2(2)(a), 903.1.1,

1101.4 , 1101.4.2.1

Drainage, changes in direction . . . . . . . . . . . . . . .706.0 Drainage, existing sewers . . . . . . . . . . . . . . . . . . .715.3

Drainage, horizontal slope . . . . . . . . . . . . .708.0, 718.1 Drainage, material . . . .701.2, Table 701.2, 715.1, 720.1 Exposed to sunlight,

ABS and PVC . . . . . . . . . . . . . . . . . . . . . . . . . .906.1

Fuel gas . . . . . . . . . . . . . . . . . . . . . . . . .1208.0, 1210.0 Hangers and supports . . .313.0, Table 313.3, 1210.3.5, 1210.3.5.1, Table 1210.3.5.1,

1323.4 – 1323.4.5

Table 1323.1.4(1) – Table 1323.4.4

Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .601.3

Indirect waste . . . . . . . . . . . . . . . . . . . . . . . . . . . .803.0

Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .609.12.3

Joints and connections . . .(see Joints and connections) Location (OSHPD) . . . . . . . . . . . . . . . . . . . . . . . .310.11 Medical gas, material . . . . . . . . . . . . . . . . . . . . . .1318.0 Plumbing vent, material . . . . . . . . . . .Table 701.2, 903.0 Protection of . . . . . . . . . . . . . . . . . . . . . . . .312.0, 718.3,

1210.1.3 – 1210.1.5

Rehabilitation of . . . . . . . . . . . . . . . . . . . . . . . . . .320.0

Separation in trenches . . . . . . . . . . . . . . . . . . .1505.11 Sprinkler system, lawn . . . . . . . . . . Table 610.3, 612.1, Table A 103.1, A 103.2, M 102.5 Storm drainage, materials . . . . . . . . . .1101.4 – 1101.4.6 Trenching, excavation,

and backfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314.0
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

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GENERAL REGULATIONS
CPC § 316.8 High relevance — show source text
316.8 Firewalls. A pipe sleeve through a firewall shall have the space around the pipe or tubing completely sealed with an approved fire-resistive material in accordance with other codes.

316.9 Structural Members. A structural member weakened or impaired by cutting, notching, or otherwise shall be reinforced, repaired, or replaced so as to be left in a safe structural condition in accordance with the requirements of the California Building Code or California Residential Code .

316.10 Rodentproofing. Mechanical system shall be constructed in such a manner as to restrict rodents or vermin from entering a building by following the ductwork from the outside into the building. 316.11 Metal Collars. In or on buildings where openings have been made in walls, floors, or ceilings for the passage of ductwork or pipes, such openings shall be closed and protected by the installation of approved metal collars securely fastened to the adjoining structure.

317.0 Trenching, Excavation, and Backfill.

317.1 Trenches. Trenches deeper than the footings 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 302.0.

317.2 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.

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

317.4 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, cinderfill, 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 then be 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.

318.0 Scope. 318.1 Applicability. This part is applicable to health facil- ities regulated by OSHPD.

Note: This section has no corresponding provisions in the UMC. For the scope and authority of each state agency, refer to Chapter 1. 318.2 Services/Systems and Utilities. Refer to Section 1224.4.1, 1225.2.1 and 1228.4.1.1 of the California Building Code.
CPC § 1323.4.5 High relevance — show source text
1323.4.5 Seismic Provisions. Where required, medical gas and vacuum piping shall be seismically restrained against earthquakes in accordance with the applicable building code. [NFPA 99:5.1.10.11.4.7]

1323.5 Frost Protection. Buried piping outside of buildings shall be installed below the local level of frost penetration. [NFPA 99:5.1.10.11.5.1]

TABLE 1323.4.4

MAXIMUM PIPE SUPPORT SPACING

[NFPA 99: TABLE 5.1.10.11.4.6]

For SI units: 1 inch = 25 mm, 1 foot = 304.8 mm

2025 CALIFORNIA PLUMBING CODE 293

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HEALTH CARE FACILITIES AND MEDICAL GAS AND MEDICAL VACUUM SYSTEMS

1323.5.1 Backfilling and Trenching. The installation procedure for underground piping shall protect the piping from physical damage while being backfilled.

[NFPA 99:5.1.10.11.5.2]

1323.5.2 Conduit, Cover, or Enclosure. If underground piping is protected by a conduit, cover, or other enclosure, the following requirements shall be met:

(1) Access shall be provided at the joints for visual inspection and leak testing.

(2) The conduit, cover, or enclosure shall be self-draining and not retain groundwater in prolonged contact with the pipe. [NFPA 99:5.1.10.11.5.3]

1323.5.3 Excessive Stresses. Buried piping that will be subject to surface loads shall be buried at a depth that will protect the piping or its enclosure from excessive stresses. [NFPA 99:5.1.10.11.5.4]

1323.5.4 Minimum Backfill. The minimum backfilled cover above the top of the pipe or its enclosure for buried piping outside of buildings shall be 36 inches (914 mm), except that the minimum cover shall be permitted to be reduced to 18 inches (457 mm) where there is no potential for damage from surface loads or surface conditions.

[NFPA 99:5.1.10.11.5.5]

1323.5.5 Trenches. Trenches shall be excavated so that the pipe or its enclosure has firm, substantially continuous bearing on the bottom of the trench. [NFPA 99:5.1.10.11.5.6]

1323.5.6 Composition of Backfill. Backfill shall be clean, free from material that can damage the pipe, and compacted. [NFPA 99:5.1.10.11.5.7]

1323.5.7 Marker. A continuous tape or marker placed immediately above the pipe or its enclosure shall clearly identify the pipeline by specific name. [NFPA 99:5.1.10.11.5.8]

1323.5.8 Warning. A continuous warning means shall also be provided above the pipeline at approximately one-half the depth of burial. [NFPA 99:5.1.10.11.5.9]
CPC § 313.0 Medium relevance — show source text
313.0 Hangers, Supports, and Anchors. 313.1 General. Piping, tubing, fixtures, appliances, and appurtenances shall be supported in accordance with this code, the manufacturer’s installation instructions, and in accordance with the Authority Having Jurisdiction. Seismic restraints shall be in accordance with the building code. 313.2 Material. Hangers, supports, and anchors shall be of sufficient strength to support the weight of the pipe or tubing and its contents. Piping or tubing shall be isolated from incompatible materials. 313.3 Suspended Piping. Suspended piping shall be supported at intervals not to exceed those shown in Table 313.3. 313.4 Alignment. Piping shall be supported in such a manner as to maintain its alignment and prevent sagging. 313.5 Underground Installation. 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 301.2.

313.6 Hanger Rod Sizes. Hanger rod sizes shall be not smaller than those shown in Table 313.6.

TABLE 313.6

HANGER ROD SIZES

PIPE AND TUBE SIZE
(inches) ROD SIZE
(inches)

1⁄2 – 4 3⁄8

5 – 8 1⁄2

10 – 12 5⁄8

For SI units: 1 inch = 25.4 mm

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.

PIPE AND TUBE SIZE (inches)	ROD SIZE (inches)
1⁄2 – 4	3⁄8
5 – 8	1⁄2
10 – 12	5⁄8

Frequently asked questions

How close can I dig to an existing footing?

If your trench is deeper than the footing and parallels it, locate the trench not less than 45° from the bottom exterior edge of the footing — see § 314.1 .

Do I have to leave trenches open for inspection?

Yes. Open trenches for in‑building drainage work must be kept open until the piping has been inspected, tested and accepted — § 314.3 .

What material can I use to backfill around pipe?

Use clean earth free of stones, boulders, cinders, frozen earth, construction debris or other damaging/corrosive materials; backfill in thin layers to 12 inches above pipe top and compact — § 314.4 .

Can I use heavy machinery to finish backfill right away?

Not immediately over the pipe. After initial thin-layer backfill to 12 inches above the pipe, mechanical equipment such as bulldozers/graders may be used to finish backfill to grade; fill must be properly compacted — § 314.4 .

Are there special rules for thermoplastic pipe?

Yes — the code references thermoplastic pipe installation requirements in the context of excavation/backfill (see § 314.4.1). The full text of § 314.4.1 was referenced but not included in the retrieved preview; consult the full CPC for the thermoplastic‑specific provisions .

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