What controls does Title 24 require for a hot water recirculation pump in an ADU?

On the prescriptive path, the 2025 Energy Code allows only one kind of recirculation system in a new ADU: demand recirculation with manual on/off control, built to Reference Appendix RA4.4.9 (Section 150.1(c)8). You press a button, the pump runs until hot water reaches the sensor, and it shuts off. Continuous or timer-only recirculation doesn't meet the prescriptive requirement.

Do you even need one?

Most ADUs are compact. Putting the water heater close to the kitchen and bathroom usually keeps hot water waits short without any pump. Recirculation is a fix for long runs, so consider moving the heater before adding a loop.

What RA4.4.9 requires

• On demand only. The pump starts shortly before a hot water draw, and the controls shut it off when they sense a rise in pipe temperature.
• Manual activation. A wired or wireless switch starts the pump, and controls may draw no more than 1 watt on standby.
• Switch locations. Put controls in the kitchen, the bathrooms, and at any hot water fixture at least 20 feet from the water heater, measured along the hot water piping.
• Shutoff. Either the pump stops once the temperature at the sensor rises no more than 10°F above the starting water temperature, or it won't run when the pipe is above 102°F.
• Time limit. Pump operation is limited to 5 minutes per activation, as a backstop if the normal shutoff fails.
• More than one loop is allowed, each with its own pump and controls.

Return line options

1. A dedicated return line, with the pump, controls, and sensor at the end of the supply loop, typically under a sink.
2. A pump and controls on the return near the water heater, with the sensor as close as practical to the end of the supply loop.
3. The cold water line used as the return, with the pump, controls, and sensor under the sink at the end of the hot supply. The cold line doesn't need insulation in this case.

Other rules that apply

• As a mandatory measure, any hot water system with a circulating pump must be able to turn the system off automatically (Section 110.3(c)2).
• Domestic hot water piping must be insulated per CPC Section 609.12, with limited exceptions (Section 150.0(j)).
• On the performance path, your Title 24 report can model other recirculation controls, and some credits require field verification by a rater.

What it means for your plumbing plan

Your plans should show the loop route, the return method, the pump and sensor locations, the activation switch locations, and pipe insulation, and the system type must match the Title 24 compliance form. See CALGreen plumbing requirements beyond flow rates, our Title 24 reports, and our plumbing plans.

Sources: energy.ca.gov, energy.ca.gov.