Is there an in and out for the coolant hoses to water heater?

You'd think this would be a simple Google search or could be easily found in the manual, but it is not. I would really appreciate advice from someone who knows Yanmar engines (3GM30F is mine). I have torn out the leaky water heater and was really very careful to diagram everything....except.....which way the connections were run to the radiator hoses. The water heater specifies an in and an out so I would assume the engine is the same. The engine has one hose coming from behind the water pump and the other off of the heat exchanger. Does it matter which way these hoses flow into or return from the water heater? I feel like it should, but one person I asked said it should not. I assume the flow from the heat exchanger would be the intake to the water heater and the return is toward the water pump side. What is the consensus on here