1 Scope
NOTE This standard covers standalone, in-line, and close-coupled centrifugal pumps in domestic plumbing service where a single circulator or transfer pump is the primary product of work. (1.1)
NOTE Three service classes are addressed: hot water recirculation pumps that maintain temperature in the domestic hot water loop; small cold-water transfer and booster-duty inline pumps for clean potable or utility water; and condensate transfer or removal pumps handling clean plumbing or HVAC condensate routed to a plumbing drain. (1.2)
NOTE The dominant in-scope product is the small wet-rotor in-line circulator, fractional horsepower, 115 V single-phase, plumbed into a domestic hot water recirculation loop. A close-coupled end-suction pump serves the same purpose on larger building recirculation mains and higher-flow transfer duty, and a compact demand-recirculation pump and remote sensor kit serves single-family and small dwelling-unit applications. (1.3)
NOTE The boundary of work under this standard is the pump assembly itself — the casing or volute, impeller, rotor and motor, integral or furnished isolation valves and check valve, vibration isolation provisions, controls furnished with the pump, and the connection fittings at the pump inlet and outlet. (1.4)
NOTE Adjacent standards cover work outside this boundary: (1.5)
- Recirculation and transfer piping (pipe material, joining, hangers, insulation, hydrostatic testing): Domestic Water Piping.
- Water heater or storage tank served by the loop (dedicated return port, mixing valve, storage temperature setpoint): Water Heaters.
- Disinfection and flushing of the recirculation loop after pump installation: Disinfection Of Water Systems; this standard requires the disinfection but does not restate the procedure.
- Packaged multi-pump pressure-booster skids (grossly larger in head, flow, controls, and documentation — a different product class): Domestic Water Booster Pumps. Specifying a booster-skid standard for a simple recirculation circulator is a common and costly error.
- Sump pumps, sewage ejectors, and grinder pumps with basins: Sump And Sewage Pumps.
NOTE A plumbing pump is a simple machine, but its value depends on correct selection and controls. The most common field problems are not material defects: an uncertified cast-iron body in potable service, a recirculation pump sized on fixture flow instead of pipe heat loss, a continuously running pump that violates the energy code, or a demand pump piped to the cold-water line without the temperature limit the plumbing code requires. (1.6)
1.7 Governing Standards
1.7.1All domestic water pumps shall be listed to UL 778.
1.7.2All wetted components in potable water service shall be certified to NSF/ANSI/CAN 61.
1.7.3All wetted components shall comply with NSF/ANSI/CAN 372 for lead content, with a weighted-average lead content not exceeding 0.25 percent.
1.7.4Pump nomenclature, design, selection, and performance shall conform to ANSI/HI 1.1-1.2 and ANSI/HI 1.3.
1.7.5Factory and field hydraulic performance testing shall conform to ANSI/HI 14.6.
1.7.6Motor and wiring installation shall conform to NFPA 70 (NEC), Article 430 for motors and Article 422 for appliance-cord-connected units.
1.7.7Motor efficiency, insulation class, and inverter-duty rating where a variable-speed drive is integral shall conform to NEMA MG 1.
1.7.8Demand-type recirculation controls shall conform to International Plumbing Code Section 607.4.
1.7.9Recirculation pump energy controls shall conform to ASHRAE 90.1-2022 Section 7.4.4.3 where that standard or an equivalent energy code is adopted.
2 Referenced Standards
2.1Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
2.3 Reference List
| Standard |
Title |
| UL 778 |
Motor-Operated Water Pumps (Edition 6, last revised 2024) |
| NSF/ANSI/CAN 61 |
Drinking Water System Components — Health Effects |
| NSF/ANSI/CAN 372 |
Drinking Water System Components — Lead Content |
| ANSI/HI 1.1-1.2 |
Rotodynamic Centrifugal Pumps — Nomenclature and Definitions |
| ANSI/HI 1.3 |
Rotodynamic Centrifugal Pumps for Design and Application |
| ANSI/HI 14.6 |
Rotodynamic Pumps for Hydraulic Performance Acceptance Tests |
| NFPA 70 |
National Electrical Code (Article 430 — Motors; Article 422 — Appliances) |
| NEMA MG 1 |
Motors and Generators |
| IPC |
International Plumbing Code (Section 607.4 — Hot Water Supply to Fixtures) |
| ASHRAE 90.1 |
Energy Standard for Buildings Except Low-Rise Residential Buildings (Section 7 — Service Water Heating) |
| ASHRAE Handbook |
HVAC Applications — Service Water Heating (recirculation sizing) |
| ASHRAE Guideline 12 |
Managing the Risk of Legionellosis Associated with Building Water Systems |
| AWWA C651 |
Disinfecting Water Mains |
3 Submittals
3.1 Action Submittals
3.1.1The Contractor shall submit the following action submittals for review before fabrication, ordering, or delivery:
- Product data for each pump, including type, model designation, materials of construction for all wetted parts, and rated working pressure and temperature.
- Manufacturer's pump performance curve for each pump, showing the duty point (flow and head) marked on the curve within the manufacturer's allowable operating region.
- NSF/ANSI/CAN 61 and 372 certification listings for all wetted components in potable water service.
- UL 778 listing mark or listing report for each pump.
- Electrical data: voltage, phase, full-load amperes, motor horsepower, and connection method (cord-and-plug or hard-wired).
- Control description and sequence of operation for the selected control method, including sensor locations and setpoints.
- Dimensioned installation drawings showing connection orientation, isolation and check valve arrangement, and vibration isolation provisions.
☑ Product data (type, materials, ratings)
☑ Pump performance curve with marked duty point
☑ NSF/ANSI/CAN 61 and 372 certifications
☑ UL 778 listing
☐ Electrical data
☑ Control sequence of operation
☐ Installation drawings
3.2.1The Contractor shall submit the following informational submittals:
- Factory hydrostatic and operational test reports for each pump.
- Field functional test report demonstrating that the recirculation loop maintains the required temperature at the furthest fixture.
- Disinfection and flushing record for the recirculation loop, coordinated with Disinfection Of Water Systems.
☑ Factory test reports
☑ Field functional test report
☑ Disinfection and flushing record
3.3 Closeout Submittals
3.3.1The Contractor shall submit the following closeout submittals before Substantial Completion:
- Operation and maintenance manuals for each pump, including parts lists and recommended spare parts.
- Recorded final control setpoints (time schedule, aquastat temperature, or demand sensor setpoint).
- Warranty documentation.
☑ Operation and maintenance manuals
☑ Recorded control setpoints
☑ Warranty documentation
4 Quality Assurance
4.1Each pump shall be the product of a manufacturer regularly engaged in the production of domestic plumbing pumps of the type and capacity specified.
4.2Each pump in potable water service shall bear permanent markings identifying its NSF/ANSI/CAN 61 and 372 certification.
4.3Each pump shall bear the UL 778 listing mark.
4.4Pumps of a given service class on a single project should be furnished by a single manufacturer to standardize spare parts and maintenance.
4.5Cast iron shall not be used as a wetted material in cold-water or recirculation potable service unless the specific product carries a current NSF/ANSI/CAN 61 certification for that contact.
NOTE Some older wet-rotor circulators with cast-iron bodies are listed for hydronic service only and are not certified for potable contact. (4.6)
5 Environmental and Service Conditions
5.1Wetted components shall be rated for a working pressure of not less than the value scheduled below, and not less than 125 psi in any case.
● 125 psi (standard residential and commercial)
○ 150 psi (high-pressure supply)
5.2Pump and seal materials shall be rated for continuous service at the maximum recirculation loop temperature, and not less than 160°F.
5.3The recirculation loop shall maintain a supply temperature of not less than 122°F at the furthest point in the loop, in accordance with IPC Section 607.4.
5.4Storage temperature at the water heater or tank shall not be less than 140°F to limit Legionella growth, in accordance with ASHRAE Guideline 12.
5.5The storage setpoint itself is set under Water Heaters, but the recirculation pump shall be selected to maintain loop temperature consistent with that setpoint. 5.6The pump motor and any cord-connected controls shall be located in a dry, accessible location protected from freezing and from standing water.
6 Pump Type and Service
NOTE Pump selection begins with the service class and the physical configuration. The five configurations below cover essentially all in-scope work; the wet-rotor in-line circulator is the default for hot water recirculation and the demand kit is the default for a single dwelling unit. (6.1)
6.2The pump type, service, and configuration shall be as selected below and as scheduled on the drawings.
● Hot water recirculation (temperature maintenance)
○ Cold water transfer or small booster duty
○ HVAC or plumbing condensate removal
● In-line wet-rotor circulator (single-speed)
○ In-line wet-rotor ECM variable-speed circulator
○ Demand recirculation pump and remote sensor kit
○ Close-coupled end-suction centrifugal
○ Submersible utility transfer pump
6.3 In-line wet-rotor circulator
NOTE The in-line wet-rotor circulator is a sealless pump in which the rotor runs in the pumped water and the bearings are water-lubricated; it has no mechanical seal to fail and is the overwhelmingly dominant product for residential and small commercial hot water recirculation. (6.3.1)
6.3.2A single-speed wet-rotor circulator shall be furnished where a fixed recirculation flow is acceptable and no energy-code controls modulation is required.
6.3.3An ECM (permanent-magnet electronically commutated) variable-speed circulator should be furnished where the energy code requires modulated operation, where multiple risers create a varying load, or where low-speed quiet operation is desired in a noise-sensitive occupancy.
6.3.4The wetted body of a wet-rotor circulator in potable recirculation service shall be bronze, stainless steel, or NSF-certified composite.
6.4 Close-coupled end-suction centrifugal
6.4.1A close-coupled end-suction centrifugal pump shall be furnished for higher-flow building recirculation mains and transfer duty beyond the range of a fractional-horsepower wet-rotor circulator.
6.4.2The pump casing in potable service shall be bronze, bronze-fitted, or stainless steel.
6.4.3The pump shall be furnished with a mechanical seal rated for the service temperature.
6.5 Demand recirculation pump and sensor kit
NOTE A demand recirculation kit is a compact wet-rotor pump plus a remote temperature sensor installed at the furthest fixture; the pump runs only when hot water is called for and stops when hot water reaches the sensor, eliminating continuous operation. (6.5.1)
6.5.2A demand recirculation kit shall be furnished where a dedicated return line is not available and the system ties into the cold-water supply at the furthest fixture under IPC Section 607.4.
6.5.3The kit's remote temperature sensor shall be installed at the furthest fixture served, not on the pump body or the supply riser near the heater.
7 Capacity and Head
NOTE Recirculation pump capacity shall not be selected from fixture flow rate. Recirculation flow is sized to replace the heat lost from the loop piping, computed by the ASHRAE Handbook method: recirculation flow (gpm) equals system piping heat loss (Btu/h) divided by the product of 500 and the allowable temperature drop in °F across the loop. (7.1)
7.2The allowable temperature drop across the recirculation loop used for sizing shall not exceed the value scheduled below.
7.3The recirculation pump shall be selected so that its duty point delivers not less than the scheduled flow at the scheduled head, falling within the manufacturer's allowable operating region on the published curve.
NOTE The pump shall be sized to maintain not less than 122°F at the furthest fixture under the no-load condition; undersizing by ignoring pipe heat loss produces a pump that cannot maintain loop temperature, which is the single most common recirculation failure. (7.4)
NOTE Motor horsepower shall be the smallest size that delivers the scheduled duty point; most residential and small commercial recirculation circulators fall between 1/40 HP and 1/6 HP, and large building mains rarely exceed 5 HP. (7.5)
1/40 HP
1/25 HP
1/12 HP
1/6 HP
1/4 HP
1/2 HP
1 HP
2 HP
3 HP
5 HP
8 Motor and Electrical
8.1The motor shall be of the type matched to the selected pump configuration: a permanent-magnet ECM wet rotor for variable-speed circulators, or a single-speed wet rotor or dry-rotor motor as scheduled.
● Wet-rotor single-speed
○ Wet-rotor ECM variable-speed
○ Dry-rotor (separately coupled)
8.2Electrical characteristics shall match the building power available at the pump location and shall be as scheduled.
● 115 V, 1Φ
○ 208/230 V, 1Φ
○ 208/230 V, 3Φ
○ 460 V, 3Φ
8.3The connection method shall be as scheduled; cord-and-plug connection is acceptable only where a receptacle is provided within reach and the installation complies with NEC Article 422.
● Cord-and-plug
○ Hard-wired
8.4Where a variable-speed ECM circulator is furnished, its integrated drive shall provide a control interface compatible with the building automation system where one is present.
None (standalone)
0-10 VDC analog
Dry-contact enable
BACnet MS/TP
Modbus RTU
9 Controls
NOTE The control method determines when the pump runs and is the most consequential decision in this standard, because the plumbing code and the energy code both constrain it. Continuous 24/7 operation of a recirculation pump serving dwelling units is prohibited in new construction subject to ASHRAE 90.1-2022 Section 7.4.4.3, which requires automatic controls that limit operation to periods of use. (9.1)
9.2The recirculation pump control method shall be as scheduled below.
○ Time-clock scheduling
● Aquastat (return-line temperature) control
○ Demand-signal activation (sensor or push-button)
○ Continuous operation
9.3Continuous operation shall not be specified for pumps serving dwelling units where ASHRAE 90.1-2022 or an equivalent energy code is adopted.
9.4 Time-clock and aquastat controls
9.4.1A time clock shall schedule pump operation to occupied or high-demand periods where occupancy is predictable.
9.4.2An aquastat control shall start the pump when the return-line temperature falls below setpoint and stop it when setpoint is restored.
9.4.3The aquastat sensing element shall be located on the return line near the furthest fixture, not on the pump body or the supply riser near the heater, so that it senses the temperature the control is intended to maintain.
24 hours (no scheduling)
18 hours (5 AM to 11 PM)
Occupied hours only
Two daily peak windows
9.5 Demand recirculation controls
9.5.1A demand recirculation system shall start the pump on a demand signal from a fixture sensor, motion sensor, or manual push-button and shall stop the pump when hot water reaches the remote temperature sensor.
9.5.2Where a demand recirculation system ties into the cold-water supply rather than a dedicated return line, the control shall limit the temperature of water entering the cold-water piping to not more than 104°F, in accordance with IPC Section 607.4.
NOTE Omitting the temperature sensor or using incorrect activation logic on a cold-line demand system delivers warm water at cold-water fixtures and violates IPC Section 607.4; this is a frequent and code-citable defect. (9.5.3)
9.5.4Where the recirculation return is taken from a water heater storage tank, the pump shall not continue to operate more than 5 minutes after the end of a heating cycle, in accordance with IPC Section 607.4.
NOTE A hot water branch with a developed length exceeding 50 ft from the source to the fixture without recirculation will not meet reasonable wait-time expectations, and the plumbing code effectively requires a recirculation or demand system beyond that length. (9.7)
10 Wetted Materials
10.1All wetted components in potable water service shall be NSF/ANSI/CAN 61 certified.
10.2All wetted components shall comply with NSF/ANSI/CAN 372 for lead content.
10.3The wetted material of construction shall be as scheduled below; cast iron shall not be selected for potable service unless the specific product carries a current NSF/ANSI/CAN 61 listing for that contact.
● Bronze
○ Stainless steel
○ NSF-certified composite
○ Cast iron (NSF-61 certified products only)
10.4A wet-rotor circulator selected for condensate transfer or any non-potable fluid shall be verified against the specific product's NSF listing for that fluid.
NOTE Many circulators are listed for potable water only and are not suitable for condensate or gray-water service. (10.5)
11 Connections and Valves
11.1The pump connection type and size shall match the recirculation or transfer piping it serves, as scheduled below and coordinated with Domestic Water Piping. ● Sweat (solder)
○ Threaded (NPT)
○ Flanged
○ Press
1/2 in.
3/4 in.
1 in.
1-1/4 in.
1-1/2 in.
2 in.
3 in.
4 in.
11.2Isolation valves shall be furnished on the inlet and outlet of each pump to permit removal and servicing without draining the system.
11.3A check valve shall be furnished, either integral to the pump or field-installed, to prevent reverse flow.
NOTE Without a check valve, thermal convection can drive reverse flow through an idle recirculation pump, defeating the temperature-maintenance intent and stressing the pump bearing; the check valve is not optional on a recirculation loop. (11.4)
● Integral check valve, separate isolation valves
○ Integral isolation and check valves (flange set)
○ All valves field-installed
12 Vibration Isolation and Insulation
12.1Vibration and noise transmission shall be controlled where the pump serves a noise-sensitive occupancy such as a hotel guestroom, patient room, or residential unit.
NOTE A single-speed wet-rotor circulator mounted directly on a copper line in a noise-sensitive occupancy transmits motor hum into the wall structure; an ECM variable-speed circulator running at reduced speed, combined with resilient mounting, resolves the complaint. (12.2)
12.3Vibration isolation shall be provided as scheduled below where the pump location is noise-sensitive.
● None (mechanical room, not noise-sensitive)
○ Resilient rubber-isolated unions
○ Inline flexible connectors
○ Resilient mounts plus flexible connectors
12.4A pump body insulation jacket should be provided on hot water recirculation pumps to limit heat loss from the pump body and contribute to the loop energy performance required by ASHRAE 90.1.
● Required (hot water recirculation)
○ Not required (cold water or condensate)
13 Testing
13.1 Factory Testing
13.1.1Each pump shall be hydrostatically tested at the factory at not less than 1.5 times its rated working pressure.
13.1.2Each pump shall receive a factory operational run test in accordance with ANSI/HI 14.6.
13.2 Field Testing
13.2.1After installation, the recirculation loop shall be flushed and disinfected in accordance with Disinfection Of Water Systems before the pump is placed in continuous service. NOTE Failing to flush the loop before service allows construction debris to foul the impeller and can introduce bacteria into the potable system. (13.2.2)
13.2.3The pump shall be field-tested to demonstrate that it maintains not less than 122°F at the furthest fixture under the no-load condition.
13.2.4The control sequence shall be field-tested to confirm correct start and stop response for the selected control method, including, for demand systems, the 104°F cold-line temperature limit and the post-heating-cycle run limit required by IPC Section 607.4.
13.2.5Field hydraulic performance, where verification is required, shall follow ANSI/HI 14.6.
14 Installation
14.1The pump shall be installed in the orientation recommended by the manufacturer for the rotor or bearing type; wet-rotor circulators are typically installed with the motor shaft horizontal.
14.2The direction-of-flow arrow on the pump casing shall match the intended flow direction of the loop or transfer line.
14.3Isolation valves shall be installed so the pump can be isolated and removed without draining the building loop.
14.4Unions or flange sets shall be installed at the pump connections to permit removal without cutting the piping.
NOTE The recirculation return shall be connected to a dedicated return port on the water heater or storage tank for a closed-loop system; tapping the cold-water inlet is acceptable only for a demand-type system under IPC Section 607.4. (14.5)
14.6Electrical connections shall be made in accordance with NFPA 70, with a means of disconnect provided within sight of the pump or lockable in accordance with NEC Article 430.
14.7Control sensors shall be installed at the locations specified for the selected control method before the system is energized.
14.8The pump location shall be coordinated with Domestic Water Piping so that the tie-in point, isolation valves, and access clearance are consistent between the pump and the loop. 15 Delivery, Storage, and Handling
15.1Pumps shall be delivered in the manufacturer's original packaging with connection ports capped or plugged to keep debris out of the wetted path.
15.2Pumps shall be stored indoors in a dry location protected from freezing until installation.
15.3Pumps shall be handled by the casing or designated lifting points, never by the motor leads, control cable, or sensor wiring.
16 Warranty
16.1The Contractor shall warrant each pump against defects in materials and workmanship for the period scheduled below from the date of Substantial Completion.
● 1 year
○ 2 years
○ 3 years
16.2Manufacturer's extended warranties on the motor or electronics shall be transferred to the Owner where offered.
17 Spare Parts
17.1The Contractor shall furnish the spare parts scheduled below for each pump type installed.
☐ One spare circulator cartridge or rotor assembly per pump type
☐ One spare check valve per pump type
☑ One spare control sensor (aquastat or demand sensor) per system
☑ Gaskets and O-rings for one pump
17.2Spare parts shall be delivered in labeled packaging identifying the pump type and the part, and shall be turned over to the Owner at Substantial Completion.