Domestic Hot Water Distribution System Checklist

by Doug Page, PE, LEED AP

Design Phase

• Explicitly document pipe design criteria.
• Calculate flow rate using ASPE/ASHRAE-recommended protocol. If calculations are not performed, minimally use recommended heuristics for pipe sizing and loop flow rates.
• Calculate system pressure drop for return and supply pipe, fittings, and valves. Contact heater manufacturer for published pressure drop. Size water circulator accordingly.
• Ensure that the control sequence of the circulators meets the owner’s needs and is compatible with the system equipment, such as the heater and mixing valve.
• Show balancing valves on domestic hot water return loops and pump discharge.
• Show flow rates on drawings.
• Explicitly specify balancing of the domestic water system.
• Specify maximum lead content of balancing valves.
• Show insulation on the supply and return piping.
• Show air vents at the tops of risers.
• Size expansion tanks.

Construction Phase

• Verify general installation including pipe sizing, insulation thickness, integrity/continuity of insulation, balancing valve types and locations, air vent locations, and pipe supports.
• Inspect for cross-connected water pipes during construction.
• Flush (and disinfect) domestic system.
• Field adjust shower mixing valves. Commission the master mixing valve.
• Balance the distribution system. Review balancing report.
• Adjust air pressure in expansion tanks.
• In a commercial kitchen, verify maximum time for hot water with appropriate jurisdiction (e.g., local health department and/or U.S. Department of Agriculture).