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Old 08-12-2016, 09:04   #1
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Hot water on demand?

I just saw this product "Coleman Hot Water on Demand H2Oasis Portable Water Heater" on amazon. Its a instant water heater built for camping that runs on propane and is 12v for $270.

Am I missing something because this seems perfect for a boat but have not seen much written on it. I would love to get rid of my bulky old hot water tank for something like this if it would work.

Coleman claims it can heat 40 gallons of water on one 16.5 oz propane bottle to 125deg

Anybody on here heard of someone trying this?
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Old 08-12-2016, 11:36   #2
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Re: Hot water on demand?

Several threads here on instant propane hot water heaters aboard (not this one in particular). The big issue is propane saftey. Also ducting the flue vent.

Ive got them ashore, but they are all installed in very well ventilated areas. Outside with just a small roof section for weather protection is best, but that would look like hell on a boat.

They are finiky about flow and pressure rates too so lowish flow rates of boat pressure water systems could be problematic.
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Old 08-12-2016, 12:07   #3
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Re: Hot water on demand?

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Originally Posted by AMFE View Post
I just saw this product "Coleman Hot Water on Demand H2Oasis Portable Water Heater" on amazon. Its a instant water heater built for camping that runs on propane and is 12v for $270.

Am I missing something because this seems perfect for a boat but have not seen much written on it. I would love to get rid of my bulky old hot water tank for something like this if it would work.

Coleman claims it can heat 40 gallons of water on one 16.5 oz propane bottle to 125deg

Anybody on here heard of someone trying this?
There are a few disadvantages:

1. You can't store or use it inside the boat according to ABYC and other codes. And irrespective of codes -- why would you take the risk?

2. 40 gallons of hot water is less than 4 tanks of hot water on my boat. Even much less since my hot water is 80C, not 125F. How many bottles of propane do you need to carry for a month-long cruise?


There's a pretty good reason for the existence of normal calorifiers.
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Old 08-12-2016, 12:40   #4
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Re: Hot water on demand?

It's meant for camping and outdoor use. If you want to shower on deck it might be nice.

It really doesn't replace a conventional water heater plumbed into the boat.
Isotherm SPA Water Heaters

An alternative to the Coleman gadget would be to just heat water on your stove.
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Old 08-12-2016, 12:52   #5
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Re: Hot water on demand?

Quote:
Originally Posted by AMFE View Post
I just saw this product "Coleman Hot Water on Demand H2Oasis Portable Water Heater" on amazon. Its a instant water heater built for camping that runs on propane and is 12v for $270.

Am I missing something because this seems perfect for a boat but have not seen much written on it. I would love to get rid of my bulky old hot water tank for something like this if it would work.

Coleman claims it can heat 40 gallons of water on one 16.5 oz propane bottle to 125deg

Anybody on here heard of someone trying this?
Wouldn't have these on my boat. Cheap consumer grade junk. Give them a sniff of salt water and see what happens.

sv Sedoza Sakona Liberty 458 hull 12
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Old 08-12-2016, 13:25   #6
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Re: Hot water on demand?

Absolutely nothing about this product comes close to ABYC Standards. Your insurance company will likely object if it shows up in a survey and I'd object if you showed up in a slip next to me. If I did object I'd probably have the full support of the marina.
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Old 08-12-2016, 20:25   #7
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Re: Hot water on demand?

There are some that use the instant gas fired water heaters aboard boats and they seem to work well enough. Mounted on the aft pushpit with a deck shower would be fine. That was my idea at one time.

As to ABYC A-07, 46cfr 184.200 which lists it for commercial vessels in the USA. Oddly enough there are instant water heaters that would (or could) more then comply with A-07 which is not very strict, in my eyes. Though the camping ones would be / could be unsafe. Far too many ways for it to catch the boat on fire.

I've considered it. but decided not to for one reason. The instant water heater takes a minute or two to really heat up. so that's a gallon or so of fresh water down the drain every time you start it up. They suck up the propane too.

For $270 you can buy a small 6 gallon marine electric water heater and connect it to the cooling loop engine. That would last about 5 years of near daily use. Plus potential fire issues become a non-issue. Plus 6 more gallons of potable water aboard.
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Old 08-12-2016, 20:28   #8
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Re: Hot water on demand?

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An alternative to the Coleman gadget would be to just heat water on your stove.
I've been doing just that for years. Mix in a 2 gallon garden sprayer ($12) and you have a deck shower for year round enjoyment... Er. well it's warm water anyway.
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Old 08-12-2016, 21:32   #9
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Re: Hot water on demand?

Thanks for the input. Sounds like it would be better suited for Elk camp as it is marketed. Thought I would ask anyway.

Thanks for your thoughts.
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Old 09-12-2016, 04:50   #10
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Re: Hot water on demand?

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As to ABYC A-07, 46cfr 184.200 which lists it for commercial vessels in the USA. Oddly enough there are instant water heaters that would (or could) more then comply with A-07 which is not very strict, in my eyes.
A-07 may not be "very strict" because it does not apply to propane ...

EXCEPTION: Heating appliances and systems fueled by liquefied petroleum gas (LPG), compressed natural gas (CNG), and heating systems that produce steam in a boiler are not covered by this standard.
NOTE: For requirements relating to LPG and CNG fuel systems, refer to ABYC A-1, Marine Liquefied Petroleum Gas (LPG) Systems, ABYC A-22, Compressed Natural Gas (CNG) Systems. ABYC A-26, LPG and CNG Fueled Appliances, contains requirements for all gaseous fueled appliances,
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Old 09-12-2016, 05:27   #11
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Re: Hot water on demand?

The Coleman unit is pretty neat in that it incorporates an battery electric pump and shower handset so does not need pressurised water just a bucket or container of water will do. I looked at getting one for our previous boat which did not have pressurised or hot water (outboard) but they were not available in UK. The plan was to set it up on deck and either shower in the cockpit (UK weather?) or poke the handset through the WC portlight. Store it as you do a normal lpg bottle and I do not see that arrangement is unduly risky, more than say a portable gas camping lantern or gas stove which are used in small boats regularly.
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Old 09-12-2016, 05:58   #12
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Re: Hot water on demand?

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For $270 you can buy a small 6 gallon marine electric water heater and connect it to the cooling loop engine. That would last about 5 years of near daily use. Plus potential fire issues become a non-issue. Plus 6 more gallons of potable water aboard.
Why do you say 5 yrs, don't they typically last much longer than that?
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Old 09-12-2016, 06:08   #13
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Re: Hot water on demand?

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Wouldn't have these on my boat. . . .Give them a sniff of salt water and see what happens.
This is a good point, in addition to everything else which has been said.

A bit of salt water/ salt air corrosion, and what little safety this device ever had in the first place is out the window . . .


I agree that they are not suitable for use on a boat, even if normally kept in the gas locker.
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Old 09-12-2016, 06:08   #14
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Re: Hot water on demand?

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Why do you say 5 yrs, don't they typically last much longer than that?
There is no reason the inexpensive aluminum tank heaters cannot last for decades .... if properly installed.
I've seen thousands of corroded/leaking tanks and virtually all had the same installation error. They are most often installed directly on a plywood deck where water can collect. The water is absorbed by the fiberglass batting (insulation) and poultice corrosion is the result. Those tanks come with two small mounting flanges. If you put 1/2" thick plastic plates under those flanges to create an airspace under the unit it can (mine has) last for decades.
Another help is to attach a hose from the pressure relief valve and the drain valve leading to the bilge, this helps keep more water away from the batting.
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Old 09-12-2016, 06:11   #15
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Re: Hot water on demand?

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There is no reason the inexpensive aluminum tank heaters cannot last for decades .... if properly installed.
I've seen thousands of corroded/leaking tanks and virtually all had the same installation error. They are most often installed directly on a plywood deck where water can collect. The water is absorbed by the fiberglass batting (insulation) and poultice corrosion is the result. Those tanks come with two small mounting flanges. If you put 1/2" thick plastic plates under those flanges to create an airspace under the unit it can (mine has) last for decades.
Another help is to attach a hose from the pressure relief valve and the drain valve leading to the bilge, this helps keep more water away from the batting.
I had an expensive all-copper one which only lasted 10 years. I was disappointed with that. Developed pin hole leaks which I could not solve by re-brazing. The brazing kept cracking when the calorifier vessel went through its expansion/contraction cycle when heat cycling.
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