This is an interesting topic for discussion on a cold winter's day, but in
the end it really doesn't matter. As a safety issue, how many of you drink
hot water? I might draw some hot water to boil some pasta in, so I might
ingest a little bit. But I never drink it. I might draw some hot water to
heat up on the stove to make tea. But after thinking about it just now, I
won't do that.
I thought all of this through some years ago (on a cold winter's day) and
decided it really didn't matter from a safety standpoint. But yes, engine
coolant can get in the hot water system, irrespective of what Raritan may
say. I routinely shut off the fresh water pump under way and when the
pressure finally leaks down, it is possible for coolant to leak into the
"potable" water heat exchanger. A good way to mitigate this problem is to
keep your fresh water system tight. Mine will hold its pressure for many
hours, maybe days.
The two ways to resolve this don't make sense: use of propylene glycol
antifreeze (pg is non toxic) in my engine's coolant system and the use of a
"double wall" heat exchanger. Double wall heat exchangers don't exist AFAIK.
You can do the same thing with a closed loop intermediate system. You could
install a closed loop propylene glycol system with a separate heat exchanger
and pump to isolate your boat's engine cooling system from your hot water
heat exchanger. Some boats do this if they have separate propylene glycol
system for space heating, but the vast majority do not.
And propylene glycol antifreeze isn't compatable with my engine's cooling
sytem, only a special ethylene glycol antifreeze that won't cause problems
with the aluminum head is compatable.
So take some sensible precautions like not using hot water to make tea and
you will be safe.
David
This is an interesting topic for discussion on a cold winter's day, but in
the end it really doesn't matter. As a safety issue, how many of you drink
hot water? I might draw some hot water to boil some pasta in, so I might
ingest a little bit. But I never drink it. I might draw some hot water to
heat up on the stove to make tea. But after thinking about it just now, I
won't do that.
I thought all of this through some years ago (on a cold winter's day) and
decided it really didn't matter from a safety standpoint. But yes, engine
coolant can get in the hot water system, irrespective of what Raritan may
say. I routinely shut off the fresh water pump under way and when the
pressure finally leaks down, it is possible for coolant to leak into the
"potable" water heat exchanger. A good way to mitigate this problem is to
keep your fresh water system tight. Mine will hold its pressure for many
hours, maybe days.
The two ways to resolve this don't make sense: use of propylene glycol
antifreeze (pg is non toxic) in my engine's coolant system and the use of a
"double wall" heat exchanger. Double wall heat exchangers don't exist AFAIK.
You can do the same thing with a closed loop intermediate system. You could
install a closed loop propylene glycol system with a separate heat exchanger
and pump to isolate your boat's engine cooling system from your hot water
heat exchanger. Some boats do this if they have separate propylene glycol
system for space heating, but the vast majority do not.
And propylene glycol antifreeze isn't compatable with my engine's cooling
sytem, only a special ethylene glycol antifreeze that won't cause problems
with the aluminum head is compatable.
So take some sensible precautions like not using hot water to make tea and
you will be safe.
David
