The first thing which I notice is that the flow value seems to be coming from the water heater?
Normally the flow values would come from the terminal appliances, so the basin family would include either fixed flow values or fixture unit values for each of the hot, cold and sanitary connections. These values would then transfer into the pipes at the pipe connectors in the basin family, travel along the pipes and then transfer the values to the water heater.
The water pipe connectors in the basin family would be domestic hot water and domestic cold water, both with direction “in”, “preset” and the flow value at each connector would normally be associated to a corresponding shared parameter in the family.
The water connectors on the water heater would have direction “out” and be set to “calculated”.
If you use fixture units rather than fixed flows then be aware that you must use the values in the International Plumbing Code rather than your local methods - I used CIBSE values the first time and got crazy flow values and pipe sizes.
