Insulation must meet the requirements specified in §150.0(j). Pipe insulation shall fit tightly to the pipe and all elbows and tees shall be fully insulated. No piping should be visible due to insulation voids with the exception of the last segment of piping that penetrates walls and delivers hot water to the sink, appliance, etc. All domestic hot water piping shall be insulated as specified in Section 609.12 of the California Plumbing Code.

Pipe insulation may be omitted where hot water distribution piping is buried within attic, crawlspace or wall insulation, as described below: In attics and crawlspaces the insulation shall completely surround the pipe with at least 1 inch of insulation and the pipe shall be completely covered with at least 4 inches of insulation further away from the conditioned space. In walls, the insulation must completely surround the pipe with at least 1 inch of insulation. If burial within the insulation does not meet these specifications, then this exception does not apply, and the section of pipe not meeting the specifications must be insulated as specified in §150.0(j).

The Standard Distribution System design requires that hot water distribution piping meets the requirements of Proper Installation of Pipe Insulation RA4.4.1.

To receive the thermostatic balancing valve credit, calculations shall be completed that demonstrate that the length of the return piping portion of the domestic hot water recirculation loop does not exceed 160 feet. If the domestic hot water has multiple recirculation pipe loops, the length of any hot water return pipe shall not exceed 160 feet to receive credit.

A variable speed circulation pump with pump differential pressure control shall be installed. The circulation pump design flow rate should be calculated to meet the design hot water return temperature based on the calculated distribution system heat losses and the design hot water supply temperature. The circulation pump specified should be the smallest pump required to meet the design flow rate as calculated and documented by the responsible person associated with the project.

Each thermostatic balancing valve shall be installed after the last fixture on the hot water supply riser it serves. As part of the installer’s start-up procedure, the installer shall perform the following:

1. Close all fixtures in the domestic water system.
2. Start the circulation pump at a constant speed, targeting the circulation pump design flow, and allow the system 60 minutes to warm up.
3. Verify that the temperature at the last riser does not exceed 120°F.
4. If the temperature at the last riser exceeds 120°F, adjust the pump speed down and repeat the procedure, allowing 30 minutes for warm up.
5. Once the temperature at the last riser is equal to or less than 120°F, record the pump differential pressure and set the pump into differential pressure control mode using the recorded differential pressure as the set point.

This hot water distribution system is comprised of one or more manifolds located relatively close to the water heater and pipes running from the manifold to individual fixtures and appliances. The manifolds may have valves for each pipe running from the manifold to individual fixtures and appliances. These valves must be readily accessible in accordance with the plumbing code. The measured length of pipe from the water heater each central manifold shall not exceed 15 feet (measured to the nearest half foot).

The hot water distribution system piping from the manifold to the fixtures and appliances must take the most direct path. For example, in a house with more than 1-story and the water heater in the garage, this requirement would exclude running hot water supply piping from the manifold to the attic, and then running the line back down to a first floor point of use.

The hot water distribution piping must be separated by at least two inches from any other hot water supply piping, and at least six inches from any cold water supply piping or the hot water supply piping must be insulated based on the conductivity range in Table 120.3-A and the insulation level shall be selected from the fluid temperature range based on the thickness requirements in Table 120.3-A.

Other hot water piping shall be insulated to a level that meets the requirements of §150.0(j) and be installed in accordance with Proper Installation of Pipe Insulation RA4.4.1.

This measure requires that all hot water fixtures in the dwelling unit, with the exception of a stand-alone tub must use no more pipe per run than defined in Table 4.4.5. To meet this requirement most houses will require multiple water heaters.

Table 4.4.5

1. Measurements shall be made to the nearest half foot.
2. If a combination of piping is used in a single run then one half the allowed length of each size is the maximum installed length.
3. The hot water distribution system piping from the water heater(s) to the fixtures and appliances must take the most direct path. For example, in a house with more than 1-story and the water heater in the garage, this requirement would exclude running hot water supply piping from the manifold to the attic, and then running the line back down to a first floor point of use.
4. Hot water piping shall be insulated to a level that meets the requirements of §150.0(j) and be installed in accordance with Proper Installation of Pipe Insulation R4.4.1.

To receive the Compact Hot Water Distribution System credit (available for single family homes and multifamily dwellings served by individual water heaters), plan calculations must be completed that demonstrate that the water heater to fixture proximity is more compact than a threshold criteria that is defined based on the dwelling unit conditioned floor area and number of stories. Compactness is characterized by calculating the “Weighted Distance” from the water heater to key fixtures and the threshold criteria is identified by the “Qualification Distance”. (The Qualification Distance is calculated directly by the ACM.) Determination of the Weighted Distance for a particular floor plan is dependent on whether it is a non-recirculating or a recirculating distribution system, with the recirculation option only available for single family homes.

Calculation of the Weighted Distance varies depending on the type of system being installed. The calculation is based on a equation with modifications based on the distribution system type. In each case the basis of the calculation is the plan-view, straight line distance from the water heater to the center of the further use point fixture in three locations of the dwelling unit, two of which are the master bathroom and the kitchen. It is calculated using the following equation:

Weighted_Distance = x * d_MasterBath + y * d_Kitchen + z * d_FurthestThird

Where:

1. x, y, and z = Weighted Distance coefficients (unitless), see Table 4.4.6-1.
2. d_MasterBath = The plan view, straight line distance from the water heater to the furthest fixture served by that water heater in the master bathroom (feet).
3. d_Kitchen = The plan view, straight line distance from the water heater to the furthest fixture served by that water heater in the kitchen (feet).
4. d_FurthestThird = The plan view, straight line distance from the water heater to the furthest fixture served by that water heater in the furthest room⁷ in the dwelling unit (feet).
5. 
   Because the Master Bath and Kitchen have unique separate terms, the d_FurthestThird fixture must located in neither of these rooms.  The laundry room is excluded, and shall not be used as the furthest third fixture.  In multifamily cases where there is not another qualifying use point, the d_FurthestThird term equals zero. 

Table 4.4.6-1: Weighted Distance Coefficients

Note that the calculations are only based on horizontal plan view distance measurements from the center of the water heater to the center of the use point in the designated location. Vertical pipe run lengths (for example, the vertical distance from the first to second floor) is neglected in the calculations. Use points that are located on floors different than the water heater would have their location translated to the floor where the water heater is located.

In single family homes with multiple water heaters, the Weighted Distance “z term” calculation is performed for each water heater to arrive at a Furthest Third term averaged over each of the “n” water heaters installed. For a non-recirculating distribution system, the resulting Weighted Distance calculation would include the Master Bath, the Kitchen and an average of the Furthest Third term for each of the installed water heaters. (For recirculating systems, similarly the Furthest Third term would represent an average across the “n” water heaters.)

The Qualification Distance is a function of conditioned floor area (CFA), number of stories, and number of installed water heaters. The Qualification Distance for systems with multiple water heaters is identified by using the equation for the appropriate distribution system (recirculation or non-recirculation), and dividing by the number of water heaters installed as shown in the Equation below:

Qualification Distance = (a + b * CFA) / n

Where:

1. a, b    =    Qualification distance coefficients (unitless), see Table 4.4.6-2,
2. CFA    =    Conditioned floor area of the dwelling unit (ft²), and
3. n    =    Number of water heaters in the dwelling unit (unitless).

Table 4.4.6-2: Coefficients for the Qualification Distance Calculation

The supply portion of each circulation loop, the first five feet of branches off the loop and the dedicated return line are insulated based on the conductivity range in Table 120.3-A and the insulation level shall be selected from the fluid temperature range based on the thickness requirements in Table 120.3-A and the insulation shall be installed in accordance with Proper Installation of Pipe Insulation. Other hot water piping shall meet the requirements of §150.0(j) and be installed in accordance with Proper Installation of Pipe Insulation R4.4.1.

A check valve shall be installed in the recirculation loop to prevent unintentional circulation of the water (thermo-siphoning) and back flow when the system is not operating. This check valve may be included with the pump.

The hot water distribution system piping from the water heater(s) to the fixtures and appliances must take the most direct path. For example, in a house with more than 1-story and the water heater in the garage, this requirement would exclude running hot water supply piping from the water heater to the attic, and then running the line back down to a first floor point of use.

The recirculation pump can be located external to the water heater or be integral to the water heater.

The manufacturer(s) of the recirculation pump and the controls shall provide installation and operation instructions that provide details of the operation of the pump and controls and such instructions shall be available at the jobsite for inspection.

All recirculation controls with the exception of demand recirculation control systems fall under this category.

1. More than one circulation loop may be installed. Each loop shall have its own pump and controls.
2. The active control shall be either: timer, temperature, or time and temperature. Timers shall be set to less than 24 hours. The temperature sensor shall be connected to the piping and to the controls for the pump.

Demand controlled recirculation systems shall operate “on-demand”, meaning that pump operation shall be initiated shortly prior to the hot water draw. The controls shall operate on the principal of shutting off the pump with a sensed rise in pipe temperature (Delta-T). For this measure a manual switch is used to activate the pump.

1. More than one circulation loop may be installed. Each loop shall have its own pump and controls.
2. Manual controls shall be located in the kitchen, bathrooms, and any hot water fixture location that is at least 20 feet (measured along the hot water piping) from the water heater.
3. Manual controlled systems may be activated by wired or wireless mechanisms, Manual controls shall have standby power of 1 watt or less.
4. Pump and demand control placement meets one of the following criteria.

   1.  When a dedicated return line has been installed the pump, demand controls and thermo-sensor are installed at the end of the supply portion of the recirculation loop (typically under a sink); or 

   2. The pump and demand controls are installed on the return line near the water heater and the thermo-sensor is installed in an accessible location as close to the end of the supply portion of the recirculation loop as possible (typically under a sink), or 

   3. When the cold water line is used as the return, the pump, demand controls and thermo-sensor is installed in an accessible location at the end of supply portion of the hot water distribution line (typically under a sink). 

5. Insulation is not required on the cold water line when it is used as the return.
6. Demand controls shall be able to shut off the pump in accordance with one of the following two methods:

   1.    After the pump has been activated, the controls shall allow the pump to operate until the water temperature at the thermo-sensor rises not more than 10ºF (5.6 ºC ) above the initial temperature of the water in the pipe, or

   2.    The controls shall not allow the pump to operate when the temperature in the pipe exceeds 102ºF (38.9 ºC).

7. The controls shall limit pump operation to a maximum of 5 minutes following any activation. This is provided in the event that the normal means of shutting off the pump have failed.

Demand controlled recirculation systems shall operate “on-demand”, meaning that pump operation shall be initiated shortly prior to the hot water draw. The controls shall operate on the principal of shutting off the pump with a sensed rise in pipe temperature (Delta-T). For this measure a sensor control is used to activate the pump rather than a manual control.

1. When a dedicated return line has been installed the pump, demand controls and thermo-sensor are installed at the end of the supply portion of the recirculation loop (typically under a sink); or
2. The pump and demand controls are installed on the return line near the water heater and the thermo-sensor is installed in an accessible location as close to the end of the supply portion of the recirculation loop as possible (typically under a sink), or
3. When the cold water line is used as the return, the pump, demand controls and thermo-sensor is installed in an accessible location at the end of supply portion of the hot water distribution line (typically under a sink).

1. After the pump has been activated, the controls shall allow the pump to operate until the water temperature at the thermo-sensor rises not more than 10ºF ( 5.6 ºC ) above the initial temperature of the water in the pipe, or
2. The controls shall not allow the pump to operate when the temperature in the pipe exceeds 102ºF (38.9 ºC)

A recirculation temperature modulation control shall reduce the hot water supply temperature when hot water demand is determined to be low by the control system. The control system may use a fixed control schedule or dynamic control schedules based measurements of hot water demand. The daily hot water supply temperature reduction, which is defined as the sum of temperature reduction by the control in each hour within a 24-hour period, shall be more than 50 degrees Fahrenheit to qualify for the energy savings credit.

Recirculation systems shall also meet the requirements of §110.3.

Systems that qualify as a recirculation continuous monitoring systems for domestic hot water systems serving multiple dwelling units shall record no less frequently than hourly measurements of key system operation parameters, including hot water supply temperatures, hot water return temperatures, and status of gas valve relays of water heating equipment. The continuous monitoring system shall automatically alert building operators of abnormalities identified from monitoring results.

Recirculation systems shall also meet the requirements of §110.3.

Demand controlled recirculation systems shall operate “on-demand”, meaning that pump operation shall be initiated shortly prior to, or by a hot water draw. The controls shall operate on the principal of shutting off the pump with a sensed rise in pipe temperature (Delta-T). For this measure sensor or manual controls may be used to activate the pump(s).

(a) Manual or sensor controls shall be installed and if powered, have standby power of 1 watt or less. Controls may be located in individual units or on the loop. Controls may be activated by wired or wireless mechanisms, including buttons, motion sensors, door switches and flow switches.     

(b) Pump and control placement shall meet one of the following criteria:         

1. When a dedicated return line has been installed the pump, controls and thermo-sensor are installed at the end of the supply portion of the recirculation loop; or         

2.The pump and controls are installed on the dedicated return line near the water heater and the thermo-sensor is installed in an accessible location as close to the end of the supply portion of the recirculation loop as possible, or            

3. When the cold water line is used as the return, the pump, demand controls and thermosensor shall be installed in an accessible location at the end of supply portion of the hot water distribution line (typically under a sink).            

Recirculation systems shall also meet the requirements of §110.3.

Consistent with the requirements of RA3.6.2, this measure requires an ECC-rater to verify that all hot water piping is insulated correctly.

Consistent with the requirements of RA4.4.4 this measure requires an ECC-rater to verify that the length of pipe between the water heater and each central manifold does not exceed 5 feet and to verify pipe insulation.

A ECC-rater verification is required in order to obtain this credit. To meet the Compact Hot Water Distribution System Expanded Credit eligibility requirements, the requirements in RA4.4.6 must be met. In addition, the following field verifications are required:

1. No hot water piping >1” diameter piping is allowed,
2. Length of 1” diameter piping is limited to 8 ft or less,
3. Two and three story buildings cannot have hot water distribution piping in the attic, unless the water heater is also located in the attic and,
4. Eligible recirculating systems must be Verified Demand Recirculation: Manual Control conforming to RA4.4.17.

This measure shall include a visual ECC-rater inspection to verify that the demand pump, manual controls and thermo-sensor are present and operating properly.

This measure shall include a visual ECC-rater inspection to verify that the demand pump, sensor controls and thermo-sensor are present and operating properly.

For central systems with hot water piping serving multiple dwelling units master mixing valves (MMV) shall meet the following minimum specification, installation, and startup requirements.

The plumbing plans shall include the following MMV specification at a minimum:

1. Input parameters
   1. Recirculation pump flow rate
   2. Mixing valve outlet water temperature
   3. Recirculation return water temperature
   4. Mixing valve hot inlet water temperature
2. Calculated parameters
   1. Percentage of water flow returning to cold side of MMV
   2. Percentage of water flow returning to hot side of MMV
3. Manufacturer’s operating parameter
   1. Maximum water mixing ratio

Installation of MMV shall meet manufacturer’s instruction and the following requirements at a minimum:

(a)  The MMV shall be installed on the central heating plant hot water supply outlet header leading to the recirculation loop.

(b)  Check valves installed on the recirculation return line and cold-water line to inlet cold connection of MMV and on recirculation return piping leading back to storage tank or water heater.

(c)  Isolation valves installed on the inlet cold water, inlet recirculation return, inlet hot and outlet connections to MMV and on recirculation return piping connection to storage tank or water heater.

(d)  Balancing valve installed on the recirculation return piping to the water heater for MMVs that cannot 100% close the hot inlet port during operation.

(e)  Thermometers installed on the outlet of the MMV and on the recirculation return line next the water pump.

(a)  Startup testing of MMV during recirculation only operation.

1. Close all hot fixtures in the domestic water system.

2. Ensure that the water heater is operational and idling with storage tank plumbed to the mixing valve and meeting the hot inlet temperature specified in the plumbing plans.

3. Start the recirculation pump and set mixed outlet temperature or setpoint temperature on the MMV. Start the circulation pump at the specified water flow rate and adjust as needed to meet recirculation return temperature specified in the plumbing plans.

4. Let distribution system warm up and stabilize for 30 minutes and adjust mixing parameters as needed to realign with values in plumbing plans.

5. Let the recirculation pump operate for three hours without any water draws to ensure there is no temperature creep.

6. If during or after the three-hour period the MMV outlet and return temperature stays elevated by greater than 2°F and doesn’t return back to the specified temperature, then make necessary adjustments to the MMV. If temperature creep persists with mechanical MMV, adjust the balancing valve as necessary on the recirculation return line leading back to the water heater to ensure average MMV outlet temperature meets the specified temperature.

7. If adjustments are made to MMV or balancing valve in Step 6, then repeat Step 5.

(b)  Startup testing of MMV for a combination of recirculation and hot water draws.

1. Once the MMV is operational in a closed loop, make a water draw for 10 minutes using one of the following options:

A. With a shower operating at full flow at every: three dwelling units in a building with 15 or fewer dwelling units, five dwelling units in a building with 16 to 30 dwelling units, eight dwelling units in a building with 31 to 60 dwelling units, ten dwelling units in a building than 60 to 20 dwelling units, twenty dwelling units in a building with more than 200 dwelling units.

B. The hot water valve on a hose bib, mop sink, or other fixture on the branch line or location on the hot water distribution line is opened to a draw volume of 1 gpm for every: three dwelling units in a building with 15 or fewer dwelling units, five dwelling units in a building with 16 to 30 dwelling units, eight dwelling units in a building with 31 to 60 dwelling units, ten dwelling units in a building than 60 to 200 dwelling units, twenty dwelling units in a building with more than 200 dwelling units.

2. Monitor recirculation return temperature on the thermometer during the 10-minute draw period and ensure design return water temperature is maintained at the specified temperature documented in the plumbing plans.

3. If the recirculation return temperature falls more than 5°F below the specified temperature during the draw period, then adjust MMV setup to ensure compliance.

Solar water-heating systems and/or collectors shall be certified and rated by the Solar Rating and Certification Corporation (SRCC), the International Association of Plumbing and Mechanical Officials, Research and Testing (IAPMO R&T), or by a listing agency that is approved by the Executive Director.

To use collectors with the SRCC OG-100 certification and rating, the installed system shall meet the following eligibility criteria:

1. Include all of the features modeled and generated in the Commission approved solar savings fraction calculation.
2. The collectors shall be installed according to manufacturer’s instructions.
3. The collectors shall be located in a position that is not shaded by adjacent buildings or trees between 9:00 AM and 3:00 PM (solar time) on December 21.

To use a solar water-heating system with the SRCC OG-300 certification and rating, the installed system shall meet the following eligibility criteria:

1. The collectors shall face within 35 degrees of south and be tilted at a slope of at least 3:12.
2. The system shall be installed in the exact configuration for which it was rated. The system shall have the same collectors, pumps, controls, storage tank and backup water heater fuel type as the rated condition.
3. The system shall be installed according to manufacturer’s instructions.
4. The collectors shall be located in a position that is not shaded by adjacent buildings or trees between 9:00 AM and 3:00 PM (solar time) on December 21.

An ECC-rater inspection is required to obtain this credit. All DWHR unit(s) shall be certified to the Energy Commission according to the following requirements:

1. Vertical DWHR unit(s) shall be compliant with CSA B55.2 and tested and labeled in accordance with CSA B55.1 or IAPMO IGC 346-2017. Sloped DWHR unit(s) shall be compliant with IAPMO PS 92 and tested and labeled with IAPMO IGC 346-2017.
2. The DWHR unit(s) shall have a minimum rated effectiveness of 42 percent.

The ECC-rater shall verify that:

1. The make, model, and CSA B55.1 or IAPMO IGC 346-2017 rated effectiveness of the DWHR unit(s) shall match the compliance documents. The DWHR unit(s) shall also be verified as a model certified to the Energy Commission as qualified for credit as a DWHR unit(s).
2. The installation configuration (e.g., equal flow, unequal flow to the water heater, or unequal flow to the showers) and the percent of served shower fixtures shall match the compliance documents.
3. For water heating system serving a single dwelling, the DWHR system shall, at the minimum, recover heat from the master bathroom shower and must at least transfer that heat either back to all the respective showers or the water heater.
4. For central water heating system serving multiple dwellings, the DWHR system shall, at the minimum, recover heat from half the showers located above the first floor and must at least transfer that heat either back to all the respective showers or the water heater.
5. The DWHR unit(s) shall be installed within 1 degrees of the rated slope. Sloped DWHR shall have a minimum lengthwise slope of 1 degree. The lateral level tolerance shall be within plus or minus 1 degree.
6. The installation shall comply with any applicable California Plumbing Code requirements.