My heater plumping has a cross pipe with a valve before the plumbing enters the heater. I can see that this would allow all the water to flow through the heater when the valve is closed, but I don’t understand why it’s there… because it won’t stop the water from flowing through the heater when open. There’s a small leak in one of the elbows that I need to fix and I’m thinking about omitting the valve… either that or adding two valves in order to be able to completely isolate the heater if necessary. (I tried to upload a photo, but was not allowed).