Wisdom of Shut off valve in the water heater supply hose

[svnalu387]

Just replaced all the hoses for the water heater supply loop off Yanmar 3JH4E. Looking for advice on the wisdom of installing a Groco ball valve shutoff in the system to prevent excess heat in the cabin on hot days. Plus our hot water gets blazing hot! Google says I should install valves on both supply and return hoses. That has the advantage of being able to completely isolate the engine from that coolant loop, but that’s not why I’m doing it. Long motoring days gets the galley quite hot. I did replace hard water hoses with Shields 132 hose and put pipe insulation foam everywhere I could so maybe that’s enough to make a difference?

 

[Davidasailor26]

My guess is most of the heat is radiating from the engine compartment itself, with not that much from the hoses. The insulation will help with that even more. I know my cabin floor above the hoses gets warm when the engine is hot, but I don’t think it’s dramatic - rubber hoses aren’t great for transferring heat, and insulated ones are even less. As for the blazing hot water - the better way to fix that is with a thermostatic mixing valve on the tank outlet that can mix some cold water in. That way you don’t need to worry about forgetting to open and close a manual valve whenever you want hot water.

 

[Stu Jackson]

Before you do anything, you should seriously analyze just how the coolant flows to and through your engine and the water heater. It could be that a shutoff valve would interrupt the flow of coolant not only through that leg to the heater, but for the entire engine's coolant circuit.