water heater piping

I have installed new hot water heaters (2 x 40 gallon tanks) in my attic, but they are 1-2" taller than the old hot water heaters. As a result, there now isn't enough room between the top of the water heater and the bottom of the existing vent pipe (type B piping) for the vent hood to fit. I...

I would like to understand my water heater piping that looks complicated. I have a wood boiler combined with solar panels outside house that provides hot water to the propane water heater besides cold water. It would be very appreciated if someone could explain what those valves are used for and...