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Old 25-04-2007, 09:28   #1
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Water Heater experience sought

Well, the ER refit/rehab is under way, with stringer replacement soon to
come. However, the leaking POS Raritan water heater is soon to find its way
to the junkyard. It looks similar to another Raritan water heater I see in
the yard, which is to say rust stained and streaked from wherever it is that
the water came/comes out. In my case, it's a pinhole, somewhere, as it
manifests itself in not only water around the base, but steam out the top.
The six (inlet and outlet for feed and heat exchange, relief valve and
heater element) designed holes in the unit are dry...

In trying to assess the durability of (electric/heat exchange - see bottom
for discussion of "instant") water heaters, I see several iterations of

First is the Raritan, which is a glass-lined galvanized unit. Just like at
home, but you aren't usually going to have salt air around your home unit,
nor bouncing around as the earthquakes hit. I don't think I want to go that
route again, whether or not it's the most expensive around.

Second is other (also) expensive units, which have, usually, stainless steel
innards, and, occasionally, stainless steel outards. As there's no grade of
stainless I've seen which won't rust, I don't know that I have any
enthusiasm for that (SS shell) part, but the SS interior is interesting on
the basis of its inability to make AlCl crystals to clog up my water system,
and the presumption of a reasonably robust construction as compared to
Aluminum; nearly all the non-heater (water, fuel, holding) tank replacement
discussions I see wind up going to stainless (or to rotomolded, but that's
not practical for water heaters) if they don't want to suffer a leak in the
future. That suggests SS is a good way to go.

However, the third iteration is WH tanks with aluminum innards. Those are
universally inexpensive by comparison to the others (but outrageous by
comparison to HD units, not surprisingly). At least one manufacturer
proclaims that theirs are more robust (and/or the reason to buy theirs) than
SS units, as SS units have a predilection to leak at (they say) at
less-than-sufficient welds (whereas theirs are [stated to be] superior [in
part, due to the metal?] welds). Assuming those assertions to be true, I
still have an aversion to aluminum, as AlCl crystals, and other corrosion
issues, are the bane of aluminum tanks everywhere. However, not-leaking
trumps AlCl issues, because it's relatively trivial to insert a carbon
filter before the tank to filter only the supply to the hot water (our water
and fuel tanks are fiberglass) of chlorine, should any remain after watering
wherever it is we take on supplies and it makes its way to the water heater.

So, I'm looking for input on (long-term; I'd prefer not to have to do this
again very soon) experience with both SS and Aluminum interiors on hot water
heaters. I've had a recommendation for Super-Stor SS interior units, but
the only vendor I've found for them is Defender (which in itself is good,
but they're as far away from me as possible and still be in the continental
US, which means long and expensive shipping).

I've also had a recommendation for the wall-mounted units which are
essentially on-demand water heaters. They come in propane and electrical
models. I have a problem with both types, and individual problems with

The problem with both types is that there's no storage. That means that
water coming in has to be heated before it goes out; we shower with some
fairly extensive time between hot water uses (wet, soap, shave, anything
else, then rinse), which means it has to start over. One could put a unit
at each location to solve that, of course, but in our case, that's three,
and mucho dinero.

The bigger problem(s) is that the draw electrically is more than our
inverter is capable of handling (we're replacing the one which was lost to
salt water intrusion in our wreck; it's 1500W), so we can't use one of those
(the ones I've seen start at ~20A/120VAC and go up from there).

The propane ones make me nervous, in addition to the complexities of usage.
Short of placing it in the propane locker (I don't know how big they are,
but I suppose one might fit by displacing one of the two 10# bottles in
ours), I have a real problem in having "always live" propane in the boat
living space. There's also a supply issue (we'd have to run a new line to
wherever it was), so those are non-starters. OTOH, if there are users of
these units reading, I'd enjoy hearing about how you overcame those

So, please, reports of (positive or negative - a reason to avoid is as
valuable as a recommendation) experience? And for those who've bought one,
is there another vendor besides Defender for Super-Stor?

Thanks, as always.



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Old 25-04-2007, 13:21   #2
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We have discussed these options on threads on all 3 BB's. My choice was the IsoTemp unit. It heats water off the engine quickly. It keeps the water hot overnight. No venting issues. No propane supply tubing worries. I'm really pleased. It was expensive but I think it will be a great long term provider of HW.

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Old 25-04-2007, 13:35   #3
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We've been through 3 htrs in 20 yrs... 6 gal raritan types... I think that all the life you can get out of them... 5 - 6 yrs. Ours has electric coild for when you are able to plug in and the engine heat exchanger is super. They also add 6 gallons to your water capacity. I've been on a boat with a propane instant hot water. I thought it was a dumb idea... it was noisy.... and you had to start it to get hot water... yet another thing to do... it was ugly sitting on the bulkhead and it had to be vented too... and added no water capacity.

Maybe the SS ones will last a bit longer... I haven't seen rust on mine to an alarming extent.. it is mounted under the aft berth well away from salty air... and in winter provides a warm place on the bunk!
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Old 25-04-2007, 14:35   #4
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We have an On Demand Bosch 38B propane unit. It's one of the only ones that has an ODS (Oxygen Depletion Sensor). That means it does not require venting and shuts off if the oxygen level is too low. It works quite well. It ties into the same propane as the stove. We use a Sintex controller that also has a propane sensor alarm. It adds a second level of propane protection that to me seems to be a good idea. The venting of the more traditional on demand propane systems adds a level of complexity I would agree isn't that great.

Our last boat had a traditional SS engine driven / shore power driven 6 gallon heater and is now 17 years old and doing quite well. the idea of a DC power based hot water heater is not really practical.

I really can't think of anything else unless you want a solar powered sun shower. Not much volume but totally simple to use.
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Old 25-04-2007, 15:12   #5
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the beauty of instant on is that you don't need storage. we installed a house hold size model in my mother and father's house and it worked flawlessly(propane). you turned the water on and it took about 3-5 seconds to get piping hot water. yes they do make noise, but only while you use hot water. this makes them more effeciant than storage units. and if you have the proper safety sensors they are just as safe as storage
units. also they last longer because they are not mounted near bilge water/damp areas like reg. heaters. the only thing you use is a little more fuel (propane). i don't think the electric ones are as quick to heat water as the propane. if you don't like looking at it mount it in a lazzerette thats vented.
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Old 25-04-2007, 18:02   #6
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I installed a 9 gal vertical Allcraft s/s heater in 1991. It's still going strong. These are generally reputed to be the best around.

But, of course, they're expensive. I paid about $700 in 1991.

This is both 110VAC and engine hot water heated. The heating element draws about 10A.

The propane jobbies scare the hell out of me, too :-)

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Old 25-04-2007, 18:12   #7
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Skip, we have a SS Seaward with heat exchanger and aluminum Inerts and it has been running without problems or leaks for 10 years and shows no signs of giving up soon. We do shut down the 110 when not using it and turn it on 20 minutes to 1/2 hour prior to showers, dishes, etc. The rest of the time it is turned off. The engine does an nice job of heating the water and there is enough insulation that it stays hot for quite a while.
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Old 26-04-2007, 05:13   #8
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There are 10 advantages (at least) in separate dual heating source storage heaters.

1. No noise
2. No flames
3. No additional use of fuel
4. No unsightly device sitting on bulkhead
5. No need to light pilot
6. additional water storage capacity
7. uses heat from engine - no additional energy used (which typically runs a bit each day for some purpose)
8. maintenance free and no need for gas sensor
9. works with shore power as well
10 can be installed almost anywear out of sight - easy plumbing job.
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