Water Heaters, what is this connected to the water heater

Wondering if you guys can help me define what this is connected to the water heater. Public water, well water for sprinkler system!

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State Proline Series 48 Gallon Capacity 4.5 kW Heating Input Lowboy To

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State Proline Series 48 Gallon Capacity 4.5 kW Heating Input Lowboy Top Connect Electric Water Heater