Miscellaneous Plumbing Information

10.15.2 Temperature Maintenance Where Required

  • Plumbing ExampleHeated water distribution systems in buildings where developed length of heated water piping from the source of the heated water to the farthest fixture exceeds 100 feet shall maintain heated water temperature in all supply piping to within 25 feet of any heated water outlet.
  • An approved electric heat tracing system shall be permitted to be used to satisfy the requirements of Section 10.15.2 (a).

10.15.3 Minimum Requirements for Hot Water Storage Tanks

  • Hot water storage tanks shall be adequate in size, when combined with the B.T.U.H. input of the water heating equipment to provide the rise in temperature necessary.
  • Water heaters and storage tanks shall be sized to provide sufficient hot water to provide both daily requirements and hourly peak loads of the occupants of the building.
  • Storage tanks shall be protected against excessive temperatures and pressure conditions as specified in the Code. (See Sections 3.3.8 and March 3, 2010)

10.15.4 Drainage of Hot Water Storage Tanks

Hot water storage tanks shall be equipped with a drain valve or other means of emptying the tank.

10.15.5 Pressure Marking of Hot Water Storage Tanks

Hot water storage tanks shall be permanently marked in an accessible place with the maximum allowable working pressure, in accordance with the applicable standard as listed in Table 3.1.3.

10.15.6 Mixed Water Temperature Control

  • All showers and bath/shower combinations shall be protected from excessive mixed water temperature due to fluctuations in supply water pressures or loss of the cold water supply. Protection shall be provided by thermostatic, pressure balancing, or combination control valves which shall reduce or shut off the mixed water supply if unsafe conditions occur. Valves shall have an adjustable stop to limit the movement of the control handle toward the full hot position. Thermostatic control valves shall have a maximum limit setting of 120 degrees F. Pressure balancing control valves shall be adjusted after installation to provide not more than 120 degrees F outlet temperature with normal water pressures and temperatures available.
  • Individual show and bath/shower control valves shall comply with the standard listed in Table 3.1.3.
  • In single family dwelling units having individual water heaters, the protection required by Section 10.15.6 (a) may be provided by sizing the entire water distribution piping system serving the showers or bath/showers for a maximum flow velocity of 4 feet per second at the design flow rates. The piping to be so sized shall include any sections of piping which serve both showers and other fixtures (See Table 10.15.6 for pip sizing).
  • Shower and/or bath/shower combinations may be protected by a master thermostatic control valve having a maximum setting of not more that 120 degrees F. The setting device shall be so arranged to resist tampering.
  • The temperature of water from tankless water heaters shall be controlled to permit not more that 140 degrees F when intended for domestic uses. This provision shall not supersede the requirements of paragraphs (a), (b), (c) and (d) above.

See definition for "Water Temperature Control Valve" and Table 10.15.6

Note: Temperature control devices, regardless of design, should be periodically serviced to ascertain proper functioning.

Mixed Water Temperature Control

Pipe Section Load (WSFU)

  • 6
  • 15
  • 25

Design Flow (GPM)

  • 5
  • 11
  • 17

Pipe Size (at 4FPS flow rate) 

  • 3/4
  • 1
  • 1 1/4

See Table B.7.3C and B.7.3E for larger values.

10.15.7 Thermal Expansion Control

Where a backflow prevention device, check valve or water pressure regulator is installed serving water heating equipment such that a closed system is created, a device for controlling thermal expansion shall be installed.

Exception: Instantaneous water heaters.

10.15.8 Plastic Piping

  • Plastic piping used for hot water distribution shall conform to the requirements of Section 3.4 and Table 3.4. Piping shall be water pressure rated for not less that 100 PSI at 180 degrees F.
    Note: The working pressure rating for certain approved plastic piping materials varies depending on pipe size, paper schedule and method of joining. (See Section 3.7.5).
  • Plastic pipe or tube shall not be used downstream for instantaneous water heaters, immersion water heaters or other heaters not having approved temperature safety devices.
  • Piping within two feet of flue or vent connectors shall be approved metallic pipe or tube.
  • The normal operation pressure in water distribution piping systems utilizing approve plastic pipe or tube for hot water distribution shall be not more than 80 PSI. Where necessary, one or more pressure reducing valves shall be provided to regulate the hot and cold water supply pressure to not more than 80 PSI.
  • The pressure in the piping system shall be limited by a pressure relief valve at the water heater set no higher than 100 psi. When the water is protected by a pressure relief valve or combination pressure-temperature relief valve having a pressure setting higher than 100 PSI, a separate pressure relief valve shall be provided to protect the piping. Thermal expansion shall be controlled as require under Section 10.15.7.