Fleck 5810 flow meter registering way too much flow

[Reach4]

It is my assumption that the output from the softener goes on to split in order to feed the hot water heater while also feeding all the cold lines. In this setup I'd think that running cold or hot lines would relieve any thermal expansion? Am I thinking about that wrong?

You are right. I was not thinking.

 

[Bannerman]

Gauge after check would allow me to see thermal expansion when no hot OR cold water is being used

Suggest installing 2 pressure gauges, one before the check valve and one after. If they are each calibrated to display the pre-CV pressure equally, then together, they will provide an easy method to determine the amount of pressure rise caused by thermal expansion.