Adding a Second Water Heater for a Far Bathroom: Title 24 Rules
For a bathroom that waits too long for hot water, the compliance manual offers two prescriptive fixes in an existing house: a demand recirculation system with manual on/off control, or a gas or propane tankless heater closer to the fixtures. The manual says any other type of added water heater requires performance modeling.
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The two paths the manual names
Under the manual's water heating alterations discussion, the only recirculation system allowed in an alteration is a demand system with manual on/off control (Section 150.2(b)1H ii); timer or temperature-controlled loops must be modeled. The other path is a natural gas or propane instantaneous heater placed closer to the problem fixtures. The manual says any other type may be installed only if the performance approach shows the home's energy use has not increased, although the list in Section 150.2(b)1H also names single heat pump water heaters, so ask how your department reads a second unit.
If a tankless unit is the choice
An instantaneous heater rated above 6.8 kBtu per hour needs isolation valves on both the cold supply and the hot outlet, with hose bibbs or other fittings on each valve for flushing (Section 110.3(c)6 and Section 150.0(n)3). New piping and existing accessible piping must meet the insulation rule in Section 150.0(j)1.
How the performance route looks
In the performance method the altered water heating is compared with the standard design in Table 150.2-G. The CF1R then documents the added heater and its distribution system as proposed features.
The same job inside an addition changes the answer
When an addition increases the number of water heaters, Section 150.2(a)1D applies instead: a single heat pump water heater (or one meeting NEEA Tier 3), or for additions of 500 square feet or less an electric water heater with point-of-use distribution. Manual Example 9-32 says a gas tankless heater for a 600 square foot addition is not one of the allowed prescriptive cases.
Ask before you plumb
The manual lists adding water heaters or hot water piping to an existing home as an alteration, and the building department decides what permit it needs. Pump-only fixes are on the hot water recirculation page; the water heater requirements list the options when the heater itself is replaced, and an existing heater serving an addition covers the other direction. See also the permit question and our residential reports.
Common Title 24 Questions
- When is Title 24 required for a home?
- Does a remodel need Title 24?
- Does a room addition need Title 24?
- What plans are needed for a residential Title 24 report?
- How much does a residential Title 24 report cost?
- How long does a residential Title 24 report take?
Frequently Asked Questions
The manual names a gas or propane tankless unit as the prescriptive choice for a slow fixture and says other types need the performance approach. Ask the building department how it classes a second unit.
No. It is a distribution change. Only a demand system with manual on/off control is allowed prescriptively in an alteration.
Explore Water Heaters
- Can an Existing Water Heater Serve a New Addition?
- Where Can You Install a Heat Pump Water Heater Under Title 24?
- Home Addition With a Heat Pump Water Heater: Title 24 Guide
- Can You Add a Hot Water Recirculation Pump Under Title 24?
- Do You Need a Permit to Replace an HVAC System or Water Heater in California?
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