Can I put my recirculation pump on a timer?

Not prescriptively. In an existing home the compliance manual says a timer or temperature-controlled system must be analysed on the performance approach to show energy use has not increased.

Does the push button have to be wired?

No. RA4.4.9 allows wired or wireless controls, with standby power of 1 watt or less.

Can the cold water line serve as the return?

Yes. RA4.4.9 allows it, with the pump, controls and sensor at the end of the hot water supply line, and no insulation is needed on the cold line when it is used as the return.

Can You Add a Hot Water Recirculation Pump Under Title 24?

Yes, but only one kind. Sections 150.1(c)8 and 150.2(b)1H allow a demand recirculation system with manual on/off control: a push button or wireless button starts the pump just before a draw, and a temperature sensor stops it. A timer, a temperature-controlled loop or a motion-sensor start is not allowed prescriptively, so it has to be modelled on the performance path.

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What a compliant system does

Reference Residential Appendix RA4.4.9 sets the details:

Buttons, wired or wireless with standby power of 1 watt or less, sit in the kitchen, the bathrooms and any fixture at least 20 feet from the water heater, measured along the hot water piping.
The pump stops when the pipe warms 10°F above its starting temperature, or does not run above 102°F, and never runs more than five minutes after a push.
Hot water piping takes the most direct route. It cannot climb to the attic and come back down to a first-floor fixture.
A check valve in the loop stops backflow and thermosiphoning.
The cold water line may serve as the return, and needs no insulation when it does.

Insulation on the loop

The supply side of the loop, the first five feet of each branch and any dedicated return line are insulated to Table 120.3-A (RA4.4.7.1). For water at 105 to 140°F that is 1 inch around pipe under 1 inch across and 1.5 inches for pipe from 1 inch to under 1.5 inches. All other hot water pipe follows Section 150.0(j)1, which points to Section 609.12 of the California Plumbing Code. Exceptions cover pipe through framing, pipe already surrounded by 1 inch of wall insulation, 2 inches in a crawlspace or 4 inches in an attic, and pipe in walls built to quality insulation installation.

In an existing home

The compliance manual says the only recirculation system allowed in an alteration is manual demand control. Any other change to the distribution system, such as a timer or temperature-controlled loop, has to be analysed on the performance approach to show the home’s energy use has not gone up. For piping, Section 150.2(b)1H covers newly installed and accessible existing pipe. A gas or propane instantaneous heater near the problem fixtures is the alternative the manual names. Section 110.3(c)2 separately requires any circulating pump to be able to turn itself off automatically.

Sensor starts and apartments

A motion sensor, door switch or flow switch that starts the pump is a sensor-controlled demand system (RA4.4.10), a different measure from the manual one. Loops serving several dwelling units fall under Section 110.3(c)4 instead; see multifamily water heating.

The replacement options and pipe rules for the heater itself are on water heater requirements and heat pump water heater installation. A remodel that moves fixtures is covered by remodels, and permits are the department’s call.

Common Title 24 Questions

Frequently Asked Questions

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