Regarding fresh water flushes. We also flush our entire system with fresh water (we do not have a loop for refrigerators but we also flush the pumps and lines to the toilets).
However, we do this more frequently--when we are at the dock for more than a few days and even at anchor and sometimes we use the recommended mixture of Salt-A-Way. We have been at the dock here at Cagliari for 8 days and will depart today--everything: Yanmar, Onan, AC, Anchor Wash, toilet pumps, and of course the sea chest and manifold have been in fresh water (measured at 140 ppm) the entire time. Fresh water helps disolve deposits, prevents or kills marine growth, minimizes galvanic action.
We have a ball valve that isolates water from the manifold to the Dessalator. When the Dessalator is flushed with fresh water, we let the water push back into the manifold and then shut the ball valve. This keeps the supply hose to the low pressure pump in fresh water and prevents, say Salt-A-Way from entering the Dessalator system.
When we make water at anchor we usually divert the first few minutes of production into several 5 litre jugs that we keep on the engine room floor. Usually this initial product has higher ppm and potential odor. We use this same water to flush the generator/manifold etc. when we are finished. It does not take much to flush the generator, manifold, engine, anchor wash. We think it costs about $0.10/liter to make our own water so for a buck or 2 you have more than enough fresh water to do the job.
A couple of other actions regarding fresh water. When we are at a dock and have been anchoring, we pull the chain out into a large rubber bucket that normally stores cleaning products and brushes. We fill the bucket with fresh water and let the chain soak, change the water, and then let the chain dry on deck before it goes back into the chain locker. Our guess is that most chain rust happens in the chain locker when the moist, salt laden chain sits there. This may be another reason why the overhead of the chain locker deteriorates on some Amels. If we get a chance we also spray out the inside of the chain locker.
None of these actions seem burdensome to us. If you build it into a routine, it is not complicated. A side benefit is that they let us monitor how well the impellers and pumps are pulling water.
When underway we keep a large plastic bowl in our head sinks (the kind with a soft urethane bottom on the lower third of the bowl). Most water is used for hand washing and face washing and that soapy water is just poured into the toilet and flushed....flushing it and keeping it in fresh water for periods of time as well.
Bob and Suzanne, KAIMI SM429