7.8104.8 Domestic Hot Water Expansion Tank (Potable Water)

Topic: 
Water Heating
Subtopic: 
Distribution
Desired Outcome: 
Provide for adequate expansion of domestic hot water as it is heated to prevent damage to piping and equipment
TitleSpecification(s)Objective(s)
7.8104.8a
Adequate air pressure of existing air tank

Unit will be hydraulically isolated and removed from piping and drain tank

Cap will be removed on bottom of tank

Pressure will be checked using a tire pressure gauge

Pressure will be closely matched to incoming water pressure

Ensure that expansion tank is properly charged and operating
7.8104.8b
Proper sizing of new expansion tank

Collect necessary information to determine expansion tank size, including:

  • Operating water pressure of water heater (a pressure gauge may need to be installed to verify)
  • Water heater and tank volume
  • Operating water temperature
  • Relieve valve pressure setting
  • Value of incoming street water pressure

Ensure that the newly installed expansion tank will be properly sized for the system
7.8104.8c
Precharge air pressure in new expansion tank

Using a tire pressure gauge and a tire pump to adjust as necessary, pressure in potable water expansion tank will be set to match the incoming street water pressure

Set correct air pressure for proper operation of tank
7.8104.8d
New installation location of expansion tank

Expansion tank shall be installed in accordance with the manufacturer's installation instructions

The expansion tank will be located on the cold water inlet to the water heater

The expansion tank should be located between the water heating equipment and the required shut off

Ensure correct location of tank