We have a 12 gallon water heater in an all-electric boat. As the cooler weather drops the inlet water temp, our supply of hot water for showers is becoming even more marginal. We're using a low flow shower head already, and tried using the onboard tank for showers, but it's just not enough. I've looked at tankless heaters, but we don't have enough amps to make that practical. Anybody solved this problem? thanksalot

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Harbor Master 47
Watts Bar Lake - TN River

   Obvious questions. Can you squeeze a bigger water heater in some where? Is there a way to draw the water from storage tanks rather than straight off the line? The stored water would be warmer from sitting & absorbing the interior heat maybe.
Is a re circulating loop, through a smaller amp drawing heat source possible? A JC Whitney auxiliary heater core in a box with a small electric heater blowing air over the fins? A small pump pushing the water through, over & over, raising the stored water temp.
A propane instant HWH loop, just for showers?
I'm done?????


Edited: 10/22/2007 at 05:38:25 PM by ted655

How old is the existing water heater? Do you believe it is working properly? I think the heater's thermostat should raise it to the setpoint temperature regardless of the incoming water supply temperature unless the heater simply doesn't have time to recover.

We have a 14 gl electric water heater and seem to have no problem with hot water supply for shower, dishwasher, washing machine (not all at once, of course).

We tried to reach Island Cove Marina by phone a couple of weeks ago to tie up for a couple of nights. No one answered so we docked at Marine Max for the weekend. Loved the access to downtown Chattanooga but all of the wakes from passing boats were a PITA. Does Island Cove have any slips for transient boats?

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Mike

1989 Sumerset 14x64
Twin Volvo AQ131C SP
Watts Bar Lake
Spring City, TN

All water heaters have the cold water inlet mounted on the top or side of the tank. Attached to this is a plastic pipe on the inside of the tank which delivers the cold water to to the bottom, thus pushing the hot water to the top.

When the plastic pipe breaks away due to age or too much heat applied during installation, the cold water enters enters at the top of the tank and then exits the top of the tank. Hot water will only last a few minutes.

If you have 12 gallons of hot water, you should be able to fill a twelve gallon container, or the equivilant thereof. If you can not, your plastic tube maybe not be connected.

I once had a new water heater installed in my home, and it only gave a few minutes of hot water. It was determined the plumber applied too much heat and melted the plastic off. Cold water came in the top and out the top and the hot water stayed on the bottom.

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Banana Tom

Tom has a point. On some water heaters you can unscrew the cold water inlet and the "dip tube" with it, and check.

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Willie
She's a tired old barge but she's paid for! http://s71.photobucket.com/alb...p;current=ef324993.pbw

Thanks all for ideas. Water reaches the thermostat set point after about 30 minutes. Cold water enters the tank on the side near the bottom, and hot feeds from the side near the top. But I may still have a mixing problem, because I get a little over 8 gallons of hot. I'll have to figure out how to check the mechanicals. It will be awkward, BECAUSE THIS RARITAN WATER HEATER HAS NO DRAIN!

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Harbor Master 47
Watts Bar Lake - TN River

I'm sure you're planning to tackle whatever the underlying problem might be, but I wonder, would some sort of solar pre-heater help? Those black plastic bags with shower hose attached work great for backpackers, maybe something similar would extend the shower time on your houseboat.

What do y'all know about solar water heaters? A low-tech bread-box type system, maybe? I'm thinking ahead for our boat-in-progress.

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Amelia
Edenton, NC

   Solar hot water is 1 part of solar that IS practicle. As with most things, there are various $$$ types. The more bells & whistles the higher the cost. The best employ heat exchangers, with fluids that won't freeze. Some self drain at night and others simply take the potable water & expose it directly to the sun.
With a bit of research, all the parts for a fairly sophisticated DYI system can be bought off the shelves.
Being from Arizona, I've seen SHWHs that heat a lot of water from a small box.
A little Googling will get a ton of design info & sources.
The downside is another "system" that needs attention and SOME DYIs are real ugly

I had answered this in a private e-mail sent to me at the plant. But will post here for everyone's information. You'll never get 12 gallons of hot water out of a 12 gallon water heater. There's nothing wrong with it; it's simply the way it works. There are no mixing provisions or baffles inside the tank. It is simply "cold water in at the bottom and hot water out at the top" The electric heating element is located as low as possible in the tank, so that the incoming cold water is exposed to the heating element as quickly as possible. As hot water is being drawn out of the tank, that hot water is automatically being replaced by cold water. So, after you've gotten past the halfway point, you're going to notice that the water temperature is dropping rapidly. After that, it takes 20-30 minutes for the water heater to recover and supply more hot water. You shouuld be able to get one decent shower out of a 12 gallon water heater (possibly 2, if you're quick). But you can't stay in there for 20 minutes, like at home.

To sum it all up, a 12 gallon water heater (in my opinion) is way too small for a 47 foot houseboat.

As far as the drain valve issue, Raritan water heaters, like most other marine water heaters, doesn't have a drain valve supplied with it. You have to understand that these are relatively small tanks, and it is difficult to find places to add all the necessary fittings and weld them in, and expect the tank to be reliable. However the installation instructions in the Owner's Manual call for an external drain fitting to be supplied by the installer, see schematic at bottom of page 2:

http://www.raritaneng.com/pdf_...6waterheaterv0502.pdf

I trust that this will clear up any misunderstandings.

Thanks for everyone's input. The 12 gallon was barely adequate when the inlet water temp was 70F. When it dropped to 40F, it was not. I think that the mixing issue was exacerbated by the cold water inlet being on the side rather than thru a drop tube from the top. Draining the 12 gallon was difficult, because there was a check valve on the cold inlet. (Is this code?) Because of the check, there was no way to drain the tank out the bottom. I made a mess as I removed the relief valve, then siphoned the tank thru that opening. Inspection showed sediment accumulation almost up to the element. I replaced the 12 with a 19 gallon household heater (with a drain) plumbed thru the top. Working so far.

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Harbor Master 47
Watts Bar Lake - TN River

the check valve isn't code, it is to prevent the hot water from backing up into the cold water pipes as the heater heats the water. water expands as it is heated and it will "back-up" into the cold water lines. As to why your previous heater didn't work i think you answered your own question, the sediment build-up was the cause., not the location of the cold water inlet. You are going to have to flush out your new water heater at least anually to prevent this from happening again.



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UC FANS
1999, 52' Monticello - Miller Tyme
Port of Aurora IN

SURE WISH I'D HAVE TOOK A PICTURE!!!

Spent couple of hours Sat morning replacing heat element in our less than 2 year old 20 gallon HW heater! It had so much lime deposit built up it had split in 2-3 places and no longer heated water properly. Took all night Friday night after we got to boat and turned it on, untill Sat. mornings just to get up to lukewarm! We replaced heater soon after buying boat 2 years ago, and it's only turned on on weekends. Seemed awfully soon for this drastic a failure. This particular heater does have a drain cock built in, but as tank is at or below waterline, and the only place to drain is into bilge (aluminum hull, totally dry and allways has been) and bilge pumps leave more than H W heater holds so I'd have to suck it out with wet/dry, I hooked up a small transfer pump to drain valve, turned off inlet line, and opened pop-off valve. Pumped that 20 gallons of water and no telling how much lime sludge/crud out in no time. Removed heating element and went to local Home Depot for a replacement. Before re-installing, I made a "rake" from a piece of coathanger and raked more debris up to element hole where I was able to suck it out with trusty old wet/dry vac. All in all, a job well done in a reasonable amount of time.

This was all accomplished on Sat morning. Daaaamed if just before noon Sunday wife started load of clothes in stacker/spacesaver washer/drier and I soon noticed small puddle coming out from underneath!!!!! Since seemed only to leak when filling I expected to find cracked mixing valve. After getting it out of closet and raising top, sure enough, water was "splattering" out of manufactured in vents in side of mixing chamber!!! Removed chamber to inspect and found,,,,,,,,




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LIME deposits in mixing area! Gave it a soaking in vinegar, and re-installed. Went back to functioning properly. All in all, had ENOUGHof the freakin lime deposits for one weekend!

Bob

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I carry a gun because it's too tiring carrying a cop.