Scout wrote:
How many here have a hot water heater that works with the engine's coolant system as a heat source?


Prob'ly everyone with a water heater. It's extremely common.


It is a very thin line separating that toxic material from your drinking water supply. The closed engine coolant loop may reach 15 psi when hot, and could easily outmatch the force in the fresh water system, especially if you run dry or turn off your on-demand pump for any reason. A pin hole or a crack in the hw heat exchanger could have deadly results.


True, unless you use non-toxic anti-freeze.

In my work as a boiler tech, we were never permitted to use toxic anti-freeze in boilers that produced domestic hot water (summer-winter boiler packages). I've replaced tens of those coils due to leakage!

That's a good idea. It's also a good idea to make it part of
your regular maintenance checks, insure no crossover between
the systems.

In most cases, the water tank is at a different level tha
the engine coolant receiver, so it should be fairly easy to
make a test for any leak between the two. For another, many
boats have their pressure water (potable water) system 'on'
most of the time, so any leak would pump drinking water into
the engine coolant loop while the engine was idle.

I get an effective check on ours every time I test the
engine coolant level (ie every time I start the engine).



Bart wrote:

I've sailed on many boat with these systems and it is hard to complain
about hot water.

Dang skippy!



To avoid corrosion an isolation transformer is the best option. Be
sure not to
tie the grounds on both sides together. Incoming circuit ground goes
to
the transformer case, the other goes to your vessel ground, such that
no
DC current can pass from shore power to the vessel. With such a system
you can crank up all AC appliances and forget about corrosion.


An excellent idea for more reasons than just this one.
Isolating the grounds can be a life saver. Unfortunately
these are rather expensive little bits of gear... our boat
does not currently have one, but it's on the list.

Fresh Breezes- Doug King