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Old 12-13-2017, 10:11 AM   #1
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Water Heater Size

My 20 gallon water heater has developed a leak after just 5-years. Probably partially my fault as I never installed an anode. Anyway, I need to replace it. What size do I really need. We are liveaboards; just my wife and I with an occasional couple as guests for a week or two. Would an 11 or 12 gallon heater suffice or do I need to stick with the 20 gallon? Thanks to all.
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Old 12-13-2017, 10:45 AM   #2
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Howard we have too much of a good thing. The water gets too hot. It’s quite likely because the tank is too small (small boat).
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Old 12-13-2017, 10:50 AM   #3
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With hot water, more is better.....too much is just right!
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Old 12-13-2017, 10:53 AM   #4
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Howard: We have a Raritan 12 gallon (11 gallon capacity) and live on the boat full time. It has a quick recovery time, 13 gallons per hour with the 1250 watt element plus and integral anode. The unit was on the boat when we bought it 10 plus years ago. We’ve changed the anode 3 times. I’ve never had a larger one but haven’t felt the need for a bigger one either.
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Old 12-13-2017, 11:00 AM   #5
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Often the price for a 20 vs say a 15 gallon unit are close. If you've got the space, 20 sounds good. BTW, some tanks are just junk right out of the factory. The term "glass lined" is a nice to have.
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Old 12-13-2017, 11:21 AM   #6
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good insulation is better than size to a point.

went to the 8 gallon Isotherm with only 750W element and it is way better than the cheapo stainless or aluminum 6 gallon with tbe 1500W element.

If I had the room, a good 12 gallon would be more than enough and might be hard to reheat larger sizes quickly at anchor using a genset.
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Old 12-13-2017, 11:25 AM   #7
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Put some wood blocks under it to raise it up. That should let the bottom dry out and prevent a leak.
(assuming the leak is at the bottom)
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Old 12-13-2017, 11:37 AM   #8
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We have a 6 gal and water is so hot that we have enough for a day for 2 people for shower, dishes etc but it is just enough for 2. As mine developed a leak too we are changing it for a 12 gal to get a bit more capacity.

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Old 12-13-2017, 12:01 PM   #9
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Don't forget, this is, in effect, also an extension of your freshwater holding capacity - I would vote for bigger if you have room.
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Old 12-13-2017, 02:36 PM   #10
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Bay Pelican has had a six gallon unit for now on 20 years. Have had four and five aboard. Never had a problem. Of course living at anchor we take short showers because of the value of fresh water, not hot water.

our isotherm unit stays warm from one day's running of the generator to the next.
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Old 12-13-2017, 02:43 PM   #11
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You do have a built in small heat exchange on the engine to heat the water too?

I think I have about a 6 or 7 gal. hot water heater and have never run out. It have a very fast recovery. You might consider showering with a 'close friend' too.
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Old 12-13-2017, 03:26 PM   #12
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20 sounds good. Depends on what your usage is. We had a 40 on the Hatt, no heat exchanger, never ran out even when using extravagantly when at the dock. As previously noted, gave us another 40 gallons of fresh water storage. We lived aboard full time, 2 adults, frequent guest via various other couples. We like taking long showers, and had both laundry washer and a full size household dishwasher. Based on our overall freshwater use when drawing from the tank, which I could measure very precisely via our Watercounter, I guesstimated that we could get by with a 20 or 30. there were times I considered adding yet another Watercounter (one of the best boat upgrades I ever did) to the heater's output to see how much hot water we used, but decided to spend it on diesel fuel instead.
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Old 12-13-2017, 03:55 PM   #13
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just curious. With a 20 gallon unit, what is the size of the heater, 1,500 watts, 1,000, or 750 watts? And for a 110 volt system how long does it take running the generator to heat 20 gallons?
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Old 12-13-2017, 04:07 PM   #14
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"no heat exchanger,"
Hmmm, my Lugger had a heat exchanger but I had to connect it.
My Cummins 380 has a heat exchanger that was hooked up by the builder. The only thing I can recommend is in and out quick throw valve be installed, "just in case".

Might want to check/confirmed with an engine tech.
IF you have an engine heat exchanger remember, the hot water produced will be "more hot" than just from the hot water tank. Might catch the guests off guard.
I have a red, engraved plaque glued to the inside of the shower, "Hot water is HOT".
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Old 12-13-2017, 04:17 PM   #15
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Quote:
Originally Posted by OldDan1943 View Post
...IF you have an engine heat exchanger remember, the hot water produced will be "more hot" than just from the hot water tank. Might catch the guests off guard.
I have a red, engraved plaque glued to the inside of the shower, "Hot water is HOT".
Youíre right, it can be a problem but for less than $100 you can add a mixing valve and donít have to worry about the water heater water temp. Iím surprised they arenít standard on new boat builds for the reason you mentioned.
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Old 12-13-2017, 04:21 PM   #16
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Quote:
Originally Posted by Bay Pelican View Post
just curious. With a 20 gallon unit, what is the size of the heater, 1,500 watts, 1,000, or 750 watts? And for a 110 volt system how long does it take running the generator to heat 20 gallons?
I did the math for mine the othet day....it is dependent on temperature rise.


If heating from 60 degree water versus 90 degree water in the heater and what is going in...the time is quite significant..so your question cant be answered without a few givens..
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Old 12-13-2017, 05:21 PM   #17
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I wandered down into my AT34 engine room and came up with the following about the hot water heater:
Seaward Model F-1200, 11 gallons, 120 volts.

I am making the assumption it is the standard hot water heater because if fits perfectly on the shelf.
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Old 12-13-2017, 05:22 PM   #18
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Standard for your model vessel?
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Old 12-13-2017, 05:47 PM   #19
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Standard for your model vessel?
Yes. Best guess based upon the 'fit'.
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Old 12-13-2017, 07:48 PM   #20
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Thanks for all the feedback. The water heater is in a position that requires removing exhaust components from the port engine to get it out. Called the yard I regularly use and they sent a mechanic over. Took about 2 minutes to locate a leak from the fitting that is used to drain the tank. It's a faucet tap like fitting made of plastic and screwed into a brass female fitting on the tank. It was leaking from the threads. He removed the entire fitting and replaced it with a brass plug. All is fine now. Whew!
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