[RNajarian]

Here is a pressure timeline. . .

May 4
8:00 am : System pressure 85 PSI. PRV Pressure at factory setting 85 PSI

3:00 pm : Recorded ambient outside temperature 81.5 deg F

5:00 pm : System pressure 146 PSI

8:20 pm : System pressure 106 PSI

May 5
3:00 am : Recorded outside ambient temperature 54.5 deg F

7:00 am : System pressure 85 PSI; Recorded outside ambient temperature 56 deg F

1:00 pm : System pressure 120 PSI; Recorded outside ambient temperature 77.5 deg F

3:45 pm : System pressure 140 PSI; Recorded outside ambient temperature 79 deg F

8:00 pm : System pressure 110 PSI; Recorded outside ambient temperature 71 deg F

9:00 pm : System pressure 100 PSI; Recorded outside ambient temperature 67 deg F

May 6
8:00 am : System pressure 85 PSI; Recorded outside ambient temperature 62 degrees F


Likely the heat of the garage attic where the pipes are caused the pressure increase.

The trick will be monitor temperature on a very hot day and on a very cold day.

Maybe I need an expansion tank after all. It is likely I never noticed the wide range of temperatures all these years. It makes sense the pressure rises with the heat of the garage attic during the day. I was thinking of putting an attic fan to keep the garage cool. That would keep the pipes in the ceiling 20 degrees cooler during the heat of the day.