Heater Plumbing

[MCS]

Hi. I have a small leak in one of the elbows leading to my heater. Before I replace it and duplicate the set-up, I have a question: There is a horizontal pipe that connects the inlet and outlet pipes that has a valve in it. It's clear that when this valve is closed, all of the water is directed to the heater. But if this valve is open, it does not stop the water from flowing into and out of the heater. I'm wondering if this is a common set-up? Should I instead install two valves, one on the inlet and one on the outlet, with a cross pipe below that would allow me to stop water flow through the heater (in case of a leak in the heater)?

Thanks in advance for your help!

[Denniswiseman]

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