1221.4 System Drainage — 2025 California Mechanical Code

Hydronic piping systems shall be installed to permit the system to be drained. The system

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1220.4.2 Tube Length. The maximum loop length of continuous tubing from a supply-and-return manifold arrangement shall not exceed the lengths specified by the manufacturer or, in the absence of manufacturer’s specifications, the lengths specified in Table 1220.4.2. Actual loop lengths shall be determined by spacing, flow rate, and pressure drop in accordance with the system design.

1220.4.3 Multizone Systems. In multizone systems, each zone shall have a tag or label securely affixed to the manifold to indicate the length of the loops and the area(s) served.

TABLE 1220.4.2

MAXIMUM LOOP LENGTHS FOR SNOW

AND ICE MELT SYSTEMS [1,2]

For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm

The total PE-RT and PEX loop lengths consist of two separate sections, the active loop, and the leader length. The active loop is installed within the heated slab. The leader length is the total distance to and from the manifold and heated slab, including any vertical distances. The manifolds shall be installed as close to the snow melt area as possible. In concrete use minimum Type L copper water tubing. In bituminous pavement use a Type K copper water tubing.

1220.4.4 Poured Structural Concrete Slab Sys- tems. Where tubes are embedded in a structural concrete slab, such tubes shall not be larger in outside dimension than one-third of the overall thickness of the slab and shall be spaced not less than three diameters on center except within 10 feet (3048 mm) of the distribution manifold. The top of the tubing shall be embedded in the slab not less than 2 inches (51 mm) below the surface of the finished concrete slab.

1220.4.5 Slab Penetration Tube and Joint Protec-

tion. Where embedded in or installed under a concrete slab, tubing shall be protected from damage at penetrations of the slab with protective sleeving approved by the tubing manufacturer. The space between the tubing and sleeve shall be sealed with an approved sealant compatible with the tubing. The tubing at the location of an expansion joint in a concrete slab shall be encased in a protective pipe sleeve that covers the tubing not less than 12 inches (305 mm) on either side of the joint or the tubing shall be installed below the slab. 1220.4.6 Concrete Slab Preparation. A solid foundation shall be prepared before the tubing is installed. Compaction shall be used for slabs, sidewalks, and driveways.

TABLE 1220.4.2

MAXIMUM LOOP LENGTHS FOR SNOW

AND ICE MELT SYSTEMS [1,2]

For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm

Notes: 1 The total PE-RT and PEX loop lengths consist of two separate sections, the active loop, and the leader length. The active loop is installed within the heated slab. The leader length is the total distance to and from the manifold and heated slab, including any vertical distances. 2 The manifolds shall be installed as close to the snow melt area as possible. 3 In concrete use minimum Type L copper water tubing. In bituminous pavement use a Type K copper water tubing.

270 2025 CALIFORNIA MECHANICAL CODE

HYDRONICS

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shall drain by indirect waste in accordance with Section 1001.4. Embedded piping underground or under floors is not required to be designed for draining the system.