Hvdronic Piping

This chapter covers the installation, material requirements, and testing of hydronic piping systems, including specific provisions for baseboard convectors, floor heating, and ground source heat pump loops.

M2101 — Hydronic Piping Systems Installation

M2101.1 General. Hydronic piping shall conform to Table M21 01.1. Approvedpiping, valves, fittings and connections shall be installed in accordance with the manufacturer's installation instructions. Pipe and fittings shall be rated for use at the operating temperature and pressure of the hydronic system. Used pipe, fittings' valves or other materials shall be free offoreign materials.

M2101.2 System drain down. Hydronic piping systems shall be installed to permit draining of the system. Where the system drains to the plumbing drainage system, the installation shall conform to the requirements of Chapters 25 through 32 of this code.

Exception: The buried portions of systems embedded underground or under floors.

M2101.3 Protection ofpotable water. The potable water system shall be protected from backflow in accordance with the provisions listed in Section P2902.

M2101.4 Pipe penetrations. Openings through concrete or masonry building elements shall be sleeved.

M2101.5 Contact with building material. A hydronic piping system shall not be in direct contact with any building material that causes the piping material to degrade or corrode.

M2101.6 Drilling and notching. Wood-framed structural members shall be drilled, notched or altered in accordance with the provisions of Sections R502.8, R602.6, R602.6.1 and R802.7. Holes in load bearing members of cold-formed steel light-frame construction shall be permitted only in accordance with Sections R505.2.5, R603.2.5 and R804.2.5. In accordance with the provisions of Sections R505.3.5, R603.3.4 and R804.3.4, cutting and notching of flanges and lips of load-bearing members of cold-formed steel light-frame construction shall not be permitted. Structural insulated panels (SIPs) shall be drilled and notched or altered in accordance with the provisions of Section R614.

M2101.7 Prohibited tee applications. Fluid in the supply side of a hydronic system shall not enter a tee fitting through the branch opening.

M2101.8 Expansion, contraction and settlement. Piping shall be installed so that piping, connections and equipment shall not be subjected to excessive strains or stresses. Provisions shall be made to compensate for expansion, contraction, shrinkage and structural settlement.

M2101.9 Piping support. Hangers and supports shall be of material of sufficient strength to support the piping, and shall be fabricated from materials compatible with the piping material. Piping shall be supported at intervals not exceeding the spacing specified in Table M2101.9.

M2101.10 Tests. Hydronic piping shall be tested hydrostatically at a pressure of not less than 100 pounds per square inch (690 kPa) for a duration of not less than 15 minutes.

Worked example

Scenario: An architect is designing a hydronic heating system for a new commercial building where the system will operate at 180°F (82°C) and 60 psi (414 kPa).

Explanation: According to M2101.1, all hydronic piping, valves, fittings, and connections must be specifically rated for use at or above these operating temperature and pressure conditions to ensure safety and system integrity.

M2102 — Baseboard Convectors

M2102.1 General. Baseboard convectors shall be installed in accordance with the manufacturer's installation instructions. Con-vectors shall be supported independently ofthe hydronic piping.

Worked example

Scenario: A contractor is installing baseboard convectors in a residential renovation project.

Explanation: The convectors must be independently supported by brackets or other means, rather than relying on the hydronic piping itself for support, as specified in M2102.1.

M2103 — Floor Heating Systems

M2103.1 Piping materials. Piping for embedment in concrete or gypsum materials shall be standard-weight steel pipe, copper tubing, cross-linked polyethylene/aluminum/cross-linked polyethylene (PEX-AL-PEX) pressure pipe, chlorinated polyvinyl chloride (CPVC) , polybutylene, cross-linked polyethylene (PEX) tubing or polypropylene (PP) with a minimum rating of 100 psi at 180°F (690 kPa at 82°C).

M2103.2 Thermal barrier required. Radiant floor heating systems shall have a thermal barrier in accordance with Sections M2103.2.1 through M2103.2.4.

M2103.2.1 Slab on grade installation. Radiant piping used in slab-on-grade applications shall have insulating materials having a minimum R-value of 5 installed beneath the piping. M2103.2.2 Suspended floor installation. In suspended floor applications, insulation shall be installed in the joist bay cavity serving the heating space above and shall consist of materials having a minimum R-value of 11. M2103.2.3 Thermal break required. A thermal break consisting of asphalt expansionjoint materials or similar insulating materials shall be provided at a point where a heated slab meets a foundation wall or other conductive slab. M2103.2.4 Thermal barrier material marking. Insulating materials used in thermal barriers shall be installed so that the manufacturer's R-value mark is readily observable upon inspection. Exception: Insulation shall not be required in engineered systems where it can be demonstrated that the insulation will decrease the efficiency or have a negative effect on the installation.

M2103.2.1 Slab on grade installation. Radiant piping used in slab-on-grade applications shall have insulating materials having a minimum R-value of 5 installed beneath the piping.

M2103.2.2 Suspended floor installation. In suspended floor applications, insulation shall be installed in the joist bay cavity serving the heating space above and shall consist of materials having a minimum R-value of 11.

M2103.2.3 Thermal break required. A thermal break consisting of asphalt expansionjoint materials or similar insulating materials shall be provided at a point where a heated slab meets a foundation wall or other conductive slab.

M2103.2.4 Thermal barrier material marking. Insulating materials used in thermal barriers shall be installed so that the manufacturer's R-value mark is readily observable upon inspection.

Exception: Insulation shall not be required in engineered systems where it can be demonstrated that the insulation will decrease the efficiency or have a negative effect on the installation.

M2103.3 Pipingjoints. Piping joints that are embedded shall be installed in accordance with the following requirements:

Steel pipe joints shall be welded.
Copper tubing shall bejoined with brazing material having a melting point exceeding 1,000°F (538°C).
Polybutylene pipe and tubing joints shall be installed with socket-type heat-fused polybutylene fittings.
CPVC tubing shall bejoined using solvent cementjoints.
Polypropylene pipe and tubing joints shall be installed with socket-type heat-fused polypropylene fittings.
Cross-linked polyethylene (PEX) tubing shall be joined using cold expansion, insert or compression fittings.

A table appears here in the adopted code. Refer to the official source for the full table.

Above ground.2. Embedded in radiant systems.3. Temperatures below 180°F only.4. Low temperature (below 130°F) applications only.

Above ground.2. Embedded in radiant systems.3. Temperatures below 180°F only.4. Low temperature (below 130°F) applications only.

M2103.4 Testing. Piping or tubing to be embedded shall be tested by applying a hydrostatic pressure of not less than 100 psi (690 kPa). The pressure shall be maintained for 30 minutes, during which all joints shall be visually inspected for leaks.

Worked example

Scenario: A designer is specifying materials for an in-floor radiant heating system that will be embedded within a concrete slab.

Explanation: Permitted piping materials for this application include standard-weight steel pipe, copper tubing, PEX-AL-PEX pressure pipe, CPVC, polybutylene, and PEX tubing, as per M2103.1.

M2104 — Low Temperature Piping

M2104.1 Piping materials. Low temperature pIpIng for embedment in concrete or gypsum materials shall be as indicated in Table M2101.1.

M2104.2 Pipingjoints. Pipingjoints (other than those in Section M21 03.2) that are embedded shall comply with the following requirements:

Cross-linked polyethylene (PEX) tubing shall be installed in accordance with the manufacturer's instructions.
Polyethylene tubing shall be installed with heat fusion joints.
Polypropylene (PP) tubing shall be installed in accordance with the manufacturer's instructions.

M2104.2.1 Polyethylene plastic pipe and tubing for ground source heat pump loop systems. Joints between polyethylene plastic pipe and tubing or fittings for ground source heat pump loop systems shall be heat fusion joints conforming to Section M21 04.2.1.1, electrofusion joints conforming to Section M2104.2.1.2 or stab-type insertion joints conforming to Section M2104.2.1.3. M2104.2.1.1 Heat-fusion joints. Joints shall be of the socket-fusion, saddle-fusion or butt-fusion type, fabricated in accordance with the piping manufacturer's instructions. Joint surfaces shall be clean and free of moisture. Joint surfaces shall be heated to melt temperatures and joined. The joint shall be undisturbed until cool. Fittings shall be manufactured in accordance with ASTMD 2683. M2104.2.1.2 Electrofusionjoints. Joint surfaces shall be clean and free of moisture, and scoured to expose virgin resin. Joint surfaces shall be heated to melt temperatures for the period of time specified by the manufacturer. The joint shall be undisturbed until cool. Fittings shall be manufactured in accordance with ASTM FlOSS. M2104.2.1.3 Stab-type insert fittings. Joint surfaces shall be clean and free of moisture. Pipe ends shall be chamfered and inserted into the fitting to full depth. Fittings shall be manufactured in accordance with ASTM D 2513.

M2104.2.1 Polyethylene plastic pipe and tubing for ground source heat pump loop systems. Joints between polyethylene plastic pipe and tubing or fittings for ground source heat pump loop systems shall be heat fusion joints conforming to Section M21 04.2.1.1, electrofusion joints conforming to Section M2104.2.1.2 or stab-type insertion joints conforming to Section M2104.2.1.3.

M2104.2.1.1 Heat-fusion joints. Joints shall be of the socket-fusion, saddle-fusion or butt-fusion type, fabricated in accordance with the piping manufacturer's instructions. Joint surfaces shall be clean and free of moisture. Joint surfaces shall be heated to melt temperatures and joined. The joint shall be undisturbed until cool. Fittings shall be manufactured in accordance with ASTMD 2683. M2104.2.1.2 Electrofusionjoints. Joint surfaces shall be clean and free of moisture, and scoured to expose virgin resin. Joint surfaces shall be heated to melt temperatures for the period of time specified by the manufacturer. The joint shall be undisturbed until cool. Fittings shall be manufactured in accordance with ASTM FlOSS. M2104.2.1.3 Stab-type insert fittings. Joint surfaces shall be clean and free of moisture. Pipe ends shall be chamfered and inserted into the fitting to full depth. Fittings shall be manufactured in accordance with ASTM D 2513.

M2104.2.1.1 Heat-fusion joints. Joints shall be of the socket-fusion, saddle-fusion or butt-fusion type, fabricated in accordance with the piping manufacturer's instructions. Joint surfaces shall be clean and free of moisture. Joint surfaces shall be heated to melt temperatures and joined. The joint shall be undisturbed until cool. Fittings shall be manufactured in accordance with ASTMD 2683.

M2104.2.1.2 Electrofusionjoints. Joint surfaces shall be clean and free of moisture, and scoured to expose virgin resin. Joint surfaces shall be heated to melt temperatures for the period of time specified by the manufacturer. The joint shall be undisturbed until cool. Fittings shall be manufactured in accordance with ASTM FlOSS.

M2104.2.1.3 Stab-type insert fittings. Joint surfaces shall be clean and free of moisture. Pipe ends shall be chamfered and inserted into the fitting to full depth. Fittings shall be manufactured in accordance with ASTM D 2513.

M2104.3 Raised temperature polyethylene (PE-RT) plastic tubing. Joints between raised temperature polyethylene tubing and fittings shall conform to Sections M21 04.3.1 and M2104.3.2. Mechanicaljoints shall be installed in accordance with the manufacturer's instructions.

M2104.3.1 Compression-type fittings. Where compression type fittings include inserts and ferrules or O-rings, the fittings shall be installed without omitting such inserts and ferrules or O-rings. M2104.3.2 PE-RT-to-metal connections. Solder joints in a metal pipe shall not occur within 18 inches (457 mm) of a transition from such metal pipe to PE-RT pipe.

M2104.3.1 Compression-type fittings. Where compression type fittings include inserts and ferrules or O-rings, the fittings shall be installed without omitting such inserts and ferrules or O-rings.

M2104.3.2 PE-RT-to-metal connections. Solder joints in a metal pipe shall not occur within 18 inches (457 mm) of a transition from such metal pipe to PE-RT pipe.

A table appears here in the adopted code. Refer to the official source for the full table.

M2104.4 Polyethylene/Aluminum/Polyethylene (PE-AL-PE) pressure pipe. Joints between polyethylene/aluminum/polyethylene pressure pipe and fittings shall conform to Sections M21 04.4.1 and M21 04.4.2. Mechanicaljoints shall be installed in accordance with the manufacturer's instructions.

M2104.4.1 Compression-type fittings. Where compression type fittings include inserts and ferrules or O-rings, the fittings shall be installed without omitting such inserts and ferrules or O-rings. M2104.4.2 PE-AL-PE to metal connections. Solderjoints in a metal pipe shall not occur within 18 inches (457 mm) of a transition from such metal pipe to PE-AL-PE pipe.

M2104.4.1 Compression-type fittings. Where compression type fittings include inserts and ferrules or O-rings, the fittings shall be installed without omitting such inserts and ferrules or O-rings.

M2104.4.2 PE-AL-PE to metal connections. Solderjoints in a metal pipe shall not occur within 18 inches (457 mm) of a transition from such metal pipe to PE-AL-PE pipe.

M2105 — Ground Source Heat Pump System Loop Piping

M2105.1 Testing. The assembled loop system shall be pressure tested with water at 100 psi (690 kPa) for 30 minutes with no observed leaks before connection (header) trenches are backfilled. Flow rates and pressure drops shall be compared to calculated values. If actual flow rate or pressure drop figures differ from calculated values by more than 10 percent, the problem shall be identified and corrected.

Worked example

Scenario: After installing the underground loop field for a ground source heat pump system, before backfilling the trenches.

Explanation: The installer must perform a pressure test using water at 100 psi (690 kPa) for 30 minutes, verifying no leaks are present. Additionally, flow rates and pressure drops must be compared against the system's calculated values to confirm proper installation and performance before the trenches are closed.

Frequently asked questions

What materials are allowed for hydronic piping embedded in concrete?

Standard-weight steel pipe, copper tubing, PEX-AL-PEX, chlorinated polyvinyl chloride (CPVC), polybutylene, and cross-linked polyethylene (PEX) tubing are permitted for embedment in concrete or gypsum.

How should baseboard convectors be supported?

Baseboard convectors must be supported independently of the hydronic piping, in accordance with the manufacturer's instructions.

What is the testing requirement for ground source heat pump loops?

The assembled loop system must be pressure tested with water at 100 psi (690 kPa) for 30 minutes with no observed leaks before connection trenches are backfilled. Flow rates and pressure drops shall also be compared to calculated values.