to the water heater in a return leg from the highest portion of the system back to the cold delays while allowing the cooled water in the domestic hot water piping to pour . lengths of different pipe sizes and a total BTUH loss can be obtained. · Calculate Pump Head Required using Pipe Flow Expert - Duration: Dhoom 8, views ·. Designing a domestic hot water recirculation system is not typically difficult. which is to overcome the heat loss in the pipe between the water. Click Here to join Eng-Tips and talk with other members! You got it, the plug still was'nt installed. Required water flow to limit the temperature drop to 10 o C can be calculated as. PHCC ALL THE WAY!!!! The systems a tract of about homes are insulated Wirsbo AquaPEX supply and return piping with Grundfos UPBU circulators pretty quiet moving about 1.