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.

 

[MFD]

For your 'blazing hot water' you want one of those temp-control mixers on the output side of the hot water tank.
Having (diesel engine hot) hot water is awesome for having hot water, the mixer helps with humans not being scalded by it and is a pretty standard device both for safety and comfort.

For shutoff valves on the engine coolant lines to the hot water tank - I have that.
My hot water tank is located some distance from the engine.
I have a valve on each of the two lines to the hot water tank - basically to isolate that entire portion of the coolant system.
Beyond my desire to be able to isolate the hot water tank, I have heard conflicting and weird information about trying to just put a valve on one side side of the auxiliary coolant ports of the engine for something like this. My valves are both within a few inches of the engine auxiliary coolant ports which from the factory I guess just have a plug screwed in. No idea if weird pulses can happen or something else if the water heater line doesn't have full flow and is shutoff on only one leg. I have just heard scuttlebutt on that, and I wanted to be able to isolate the entire segment anyway.
EDIT: I have a Yanmar 4JH4AE.

And YES, as another poster noted - make sure your hot water tank is off auxiliary ports on your engine pump and not part of the full flow cycle of the coolant

 

[colemj]

If you shut off the engine cooling circuit through the water tank, your engine will overheat. It has to complete that circuit.

If you want to not have the coolant circulate through the tank, you would need to make a bypass in the circuit. Two 3 port valves would work for this. Close to the engine if you don't want the heat from the hose traveling through the boat.

Mark

 

[Hello Below]

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.

Not only will adding a thermostatic mixing valve eliminate the blazing hot water, it will significantly save water that is wasted by having to adjust the temperature at the faucet.
Benefits of a Mixing Valve
There are many choices on the market but here is one as a start.
Isotherm - Mixing Valve for Regular, Basic and Slim Water Heaters

 

[Blitz]

I know there was some concern years ago that the diameter of the coil that runs through your water heater exchanger was smaller than the normal hoses you would use for this loop causing unnecessary restriction in this for your engine. Anyone ever confirm this as an issue? Think Raritan water heaters were noted.

 

[CrispyCringle]

I have the double shut off going to my hot water tank. Its nice to have, I recently had to replace the hot water tank and its nice to be able to isolate it from the engine. Another time on a passage one of the hot water hoses from the engine to the tank chaffed on the crank pulley and started leaking coolant. I caught it on a routine engine check before it was an issue. Anyway, good to have shut -offs. The hoses both tap the water pump from aux plugs on the housing.

 

[Stu Jackson]

ALL water heaters are like that. On my engine the takeoff hoses are 3/8" for a few feet, then 5/8" the 15 feet to the heater inlet. The tubes are always smaller inside.

In any event, all engine freshwater coolant water pumps can overcome the pressure drop.

Not an issue.

causing unnecessary restriction in this for your engine. Anyone ever confirm this as an issue? Think Raritan water heaters were noted.

 

[colemj]

The coolant circulating pump isn't really under much pressure at all and only needs a small differential to pump, so a small short length of narrower tubing doesn't phase it.

But it isn't infinite. I think all engines have a maximum run of external coolant hose in their specs. I suppose a narrower waterheater heat exchanger at the end of a hose run approaching maximum could possibly matter.

Mark