Water heater tech question

[wdonovan]

H310 with fresh water cooling Yanmar, but I assume most systems are similar across the mfr.
What is in the hoses from engine heat exchanger? Engine coolant or drinking water? Does the heat exchange happen at the engine heat exchanger or does antifreeze flow to the water heater which would mean the water heater houses its own heat exchanger?

 

[ggrizzard]

It should be distilled water with a 50/50 mix of anti freeze.
I can't tell you which coolant to use, as there have been several discussions
on the subject of "Green" vs "Pink" vs ???.
The water heater is a 'heat exchanger'.
But it's taking heat out of the engine coolant and then heating the fresh water
in the water tank before it goes to the engine heat exchanger .
YMMV.

 

[kappykaplan]

Hot antifreeze/water mixture passes through the water heater to heat the water in the tank.

 

[wdonovan]

Hot antifreeze/water mixture passes through the water heater to heat the water in the tank.

Hmmm that means when I drained my engine cooling system I did not drain it at the lowest point so there is colant still in the system where it passes into the water heater? This is my concern. As a level headed engineer (that’s self-proclaimed) I would have designed the system so engine coolant could be drained at the engine then drinking water could easily be drained at the water heater. Do they normally put a petcock for engine coolant on the water heater? Modl is 1998 if that matters.

 

[Claude L.-Auger]

Both answers above right on: think of your hot water tank as a still. Inside the tank is a metal pipe in which the antifreeze (coolant circulates and then returns to the engine). The heat generates though that pipe is what warms the cold water brought in from your fresh water tank. The tank also has a 110v electric heater which heats the water when your are plugged into AC. And a pressure relief valve similar to your tank at home.

 

[wdonovan]

Both answers above right on: think of your hot water tank as a still. Inside the tank is a metal pipe in which the antifreeze (coolant circulates and then returns to the engine). The heat generates though that pipe is what warms the cold water brought in from your fresh water tank. The tank also has a 110v electric heater which heats the water when your are plugged into AC. And a pressure relief valve similar to your tank at home.

Exactly what I was getting at. Yanmar would have me think I drained the cooling system completely but thats not the case because the w heater hookups are lower than engine h exchanger. Do you know if the water heaters have a petcock or other way of draining antifreeze? Without flooding the bilge with it.

 

[jssailem]

Without flooding the bilge with it.

You could let it flow into a bucket. Perhaps you remove that hose at the heat exchanger that connects to the water heater. Since the heater is lower then no coolant should flow out. Next put the hose end into a bucket. Now lower the bucket so that the hose is beneath the level of the water heater. Finally disconnect the hose to the engine. This should break the suction and the coolant in the heater will flow into the bucket. Fini...

 

[kappykaplan]

The antifreeze is part of the closed loop system for engine coolant. What you should be worried about is draining the the fresh water from the water heater. Are you not putting coolant in your engine over the winter?

 

[ggrizzard]

Or, are you trying to evacuate all water from the engine, heat exchanger AND water heater for the winter?
That method will work for winterization if you're sure most of the water is out and the valves are open.

 

[Claude L.-Auger]

When you winterize the engine, antifreeze remains in the entire system. You cannot drain the antifreeze out of the water tank and its hoses unless you install a bypass to replace the in & out hoses at the engine. You can drain the water from the tank through the spigot at the bottom. I've attached a hose to it and I let it drain to the bilge where it's evacuated by the bilge pump. Turn your fresh water pump off at the breaker panel so it doesn't try to refill the tank. Open the pressure relief valve or a hot water faucet to break the vacuum inside the tank.

 

[Bill Roosa]

Hmmm that means when I drained my engine cooling system I did not drain it at the lowest point so there is colant still in the system where it passes into the water heater? This is my concern. As a level headed engineer (that’s self-proclaimed) I would have designed the system so engine coolant could be drained at the engine then drinking water could easily be drained at the water heater. Do they normally put a petcock for engine coolant on the water heater? Modl is 1998 if that matters.

the design of boats does not always allow for "sane" engineering. It was probably more important to have the hot water tank actually fit in the boat in a convienyant place than to worry about the couple of cups of anti that stayed in the cooling system.

 

[wdonovan]

I found photos I took of the heater and there is no draincock. If I remove a hose it will flood coolant into an area that is not possible to cleanup. I do, however have an amicable solution.

I found a 8 or 10' length of stiff 1/4" nylon tubing. It will become a catheter of sorts. I will separate the heater hose at the highest point (heat exchanger) and run the catheter down through the hose to the lowest point. I can then attach it to my fluid extractor and the rest is easy.

I want to thank all who responded here for your information. I am kind of surprised Hunter doesn't address this in their manual but I'm glad at least I questioned it and got a solution.

 

[ggrizzard]

A manual? Hunter gave you a manual???
My, how times have changed!

 

[wdonovan]

Well my methods worked like a champ. I disconnected the hoses at the engine, one at a time and inserted the catheter tube all the way down to the heater then extracted every bit of coolant from the system.

As a side note: I treated the potable water system in a similar way. After pumping the tank dry I connected a hose to the heater drain and evacuated the water from the heater. After viewing a YT video of the heater cut open (courtesy some RV company), I saw that the drain is raised well off the floor of the heater so it would not completely drain it. I also saw the cold water inlet to the heater had its tube bent down. So, after the level was down to the drain cock, I disconnected the inlet hose and slid a catheter into it. It was easy to feel when it hit the floor of the tank. I then evacuated nearly every drop of water from the heater tank and buttoned everything up. All that was left was to disconnect the potable water pump at the inlet, open faucets systematicall and puff compressed air through. More work than a marina would do but I am very comfortable leaving all systems this way for winter storage. Thanks again all for the tremendously insightful input.

 

[dziedzicmj]

but why would you drain the coolant from the system? If for winterisation, it i snot necessary. If you are replacing the coolant, then you have to do that.

 

[sailme88]

The engine cooling system is a CLOSED system. It may entail sending heated anti-freeze to a hot water heater. But is is still CLOSED. In most applications, the water heater gets it's exchange right at the water pump or close by. Do your self a favor and stop thinking of the hot water as drinking water.

 

[wdonovan]

but why would you drain the coolant from the system? If for winterisation, it i snot necessary. If you are replacing the coolant, then you have to do that.

The boat is new to me so I have no way of knowing how old the coolant or what concentration. As a precaution and because I need to replace it anyway, I chose to drain now then fill and service the system in the spring.

 

[wdonovan]

The engine cooling system is a CLOSED system. It may entail sending heated anti-freeze to a hot water heater. But is is still CLOSED. In most applications, the water heater gets it's exchange right at the water pump or close by. Do your self a favor and stop thinking of the hot water as drinking water.

I have done myself that favor long time ago. I never confused engine coolant with potable water. I merely launched this thread to find out what fluid is in the hoses between the engine and water heater. I was not sure if the potable water was heated in the water heater or the heat exchanger. If the former it meant that after draining coolant from the engine hoses and block, I still had coolant in the heater hoses, which would be the lowest point. If the latter, the water would be drained when I drained the heater as the hoses would be higher than the heater. And there's no need to yell. My hearing's OK.

 

[Tally Ho]

. Do your self a favor and stop thinking of the hot water as drinking water.

What does that mean? If your water tanks are clean and your water is good, why can’t you drink the water from the water heater?

Greg

 

[sailme88]

What does that mean? If your water tanks are clean and your water is good, why can’t you drink the water from the water heater?

Greg

It means that after you winterize your lines there may still be residual anti-freeze in your lines. I realize the RV anti-freeze is " NON TOXIC"... but you just never know...So the water we drink is either out of a 2 1/2 gal water jug or from a reverse osmosis filter. As an aside, after one season, new water lines became pink...hmmm