It is purely optional. If you wish to track Flow Rate of your system or Filter Pressure - you can activate those. It is a user input that allows you to see historical data.
Flow Rate can be found 2 ways - some VS pumps provide data in GPM units. Others may have a Flow Meter in their plumbing system.
Changes in either flow rate or filter pressure can indicate a dirty filter or some other restriction in the plumbing.
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