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Old 26-11-2010, 10:43   #1
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Water Heater - What Size ?

I am replacing the tankless hot water heater with a conventional version that uses the engine or AC power to heat the water. Im looking specifically at the Isotemp models as they seem well built with good materials. I have the space for pretty much any of their units but am thinking of the Basic 30 model which is 8 gallons. Will be living aboard with wife and 2 kids but we are pretty good with water consumption. Question is whether the 8 gallon version is enough capacity or should I look to the 11 gallon model.

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Old 26-11-2010, 13:28   #2
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I would get the largest that will fit into your available space. You could be last in line for a hot shower!


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Old 26-11-2010, 13:43   #3
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I 2nd Foggysail. It's no different than land when considering water volume. 4 people & 8 gallons seems like bad news for person #3 & 4 to take a shower. Also, if your waterless isn't broken, then the best scenario is to keep it so you can take warm water and make it hot - pretty much doubling your new tank capacity.
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Old 26-11-2010, 13:55   #4
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We went from six gallons to twelve, and would not be tempted to go back. Where it makes the biggest difference is when you're anchored out for the weekend without any way to heat the water back up.
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Old 26-11-2010, 14:27   #5
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I agree with the others, though I can add a wrinkle to this:

We replaced our 11-gallon Force 10 water heater with a 6-gallon Isotemp. We went with a smaller tank, reluctantly, because the larger Isotemp would not fit in the space formerly occupied by the Force 10.

Two years later I am more than happy with the 6-gallon Isotemp. Why?

1) Because the Isotemp's insulation is superior to the Force 10, so our water is remains hotter, and consequently we need less hot water when mixing at the sink or shower.
2) Our 6-gallon Isotemp takes much less time to heat than the old 11-gallon Force 10. This is important for us, because often we motor for only 20 minutes or so - enough time to raise anchor, hoist sails, and get under way. I don't know whether the smaller Isotemp heats up more quickly than the larger one, but I suspect this is true.

On the other hand, I confess that we only take occasional, quick showers. The air's kind of chilly in Maine, and my wife and kids are often reluctant to shower at all. So if you have room for the larger tank and you like you're hot water, then go for it! My main point is simply that I am really happy with the Isotemp heat exchanger.... it heats up quickly, it keeps the water hot for a long time (24 hours and it's still warm enough for doing dishes), and (most importantly) the tank is stainless. So if you end up with the 6-gallon model it's not the end of the world.
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Old 26-11-2010, 14:47   #6
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I would recommend the 11 gallon option. When we were a family of four, parents and two children living aboard, our 12 gallon Raritan did us well. Whatever space you have availbale will best best served with the volume used for water heated.
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Old 27-11-2010, 13:23   #7
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Whatever size you get, I highly recommend making sure the tank is stainless steel - not the commonly advertised stainless steel case (which generally hides the far less desirable and reliable aluminum tank). The cost difference isn't that much, the reliability is much higher, but the search can be frustrating.

You might want to invest in a Solar Shower, which will heat water to scalding in a couple hours. I've found that showering with warm water in a too small bathroom was never as pleasant as rinsing off in the cockpit - unless you're living where the water turns solid.
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Old 27-11-2010, 13:40   #8
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Just as a matter of interest, why are you changing?
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Old 02-12-2010, 10:52   #9
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Im thinking I will go with the 8 gallon Isotemp heater as our primary liveaboard crusing grounds will be tropics so I don't think we are going to need to heat the water all that much.

Isotemp appears to be about the best made model out there from what I see and hear.

The existing gas fired unit is not ABYC compliant so insurance says no no. Replacement gas fired units that are ABYC compliant are more expensive, have complex circuit boards that can fail in a marine environment, and still leave the risk of CO poisioning on the table.

Thanks for all of your input.

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