We use one, it costs abt $150 on Ebay and I think EMT has one too.

Here's a thread I started about our application. Very useful and affordable.


Tankless water heater at the container

Another thread here...

Tankless water heater

Oops.  Me and you both

Our kitchen is far enough from out hot water heater that to get hot water, you turn on the faucet full hot and it takes almost a minute to get hot water. When we do the kitchen remodel, I am planning on installing an electric under-counter on demand water heater and run only a cold to the kitchen. Still going to keep the main tank unit. This actually gives me 2 hot water heaters (although the kitchen one is hard to use hot water elsewhere), but the idea is to save heating up/cooling off an entire line worth of water each time we need just a bit.

Sort of,  it would be something that would technically be mobile, but the units I'm referring to are slightly larger than the little camping units. The units typically run from 100 - 200 dollars, use a lp or ng connection, typically a small tank similar to one uses with gas grills, the only electricy they require are a couple of d batteries to power the igniter. They are used frequently in motor homes.  I'm not referring to replacing an existing hot water heater because I think the technology is a better or more efficient one, I don't believe that to be the case. And I was looking for anyone who had experience with these unit to share their experience with them. Do they deliver as promised, has anyone used a 12 volt pump with them, do they tend to hold up over time..

example heater

Thanks EXPY, that's the kind of info I was looking for. In your opinion are they reliable, any issues other than what you posted?

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I am using a Harbor Freight marine pump that runs on 12v and is rated for up to 35 psi which is well within the range of a normal house pressure.

35psi at what GPM?
link to HF page?

ar-jedi



Same here, that sounds like what I'm looking for.


I ASSUME this is what he's talking about... and it's 35' of head, not 35psi.

http://www.harborfreight.com/12-volt-marine-utility-water-pump-94639.html


Yes but it is rated up to 50 psi.... I will be using it around 35 psi.

Edit to include:

The water heaters are designed to work off of normal house water pressure which depending on where you live is going to average around 30-60psi. So I am working off that that pressure to make sure the tankless heater works efficiently.


http://manuals.harborfreight.com/manuals/94000-94999/94639.pdf

so, a few things:

1) every (EVERY) fluid pump has a psi vs gpm curve which characterizes how the pressure and flow interact (in general, the higher the pressure the lower the flow, right up until the pressure is so high that there is no flow; you could say that at this point the pump has "stalled" against the pressure). the above linked PDF does not provide this characteristic curve, nor does it provide a table of pressures and associated flow rates. so, it's not possible to back-of-the-napkin-calculate a system pressure vs flow scenario, given for example a few dozen feet of 1/2" pipe and a 2.5 GPM shower head.

2) the PDF does state that this pump is for intermittent use only, but provides no usage profile.
-> This utility pump is designed for intermittent use only. Do not use the utility pump over excessive lengths of time, as premature wearing will result.
it's not clear that excessive length of time means more than 2 minutes or more than 20 minutes...

3) as with any positive displacement rubber impeller pump, the impeller depends on the pumped liquid for lubrication and cooling..
->Do not allow the utility pump to run dry. Fill the pump with liquid before operation. Failing to do so may damage the seal ring (19), which depends on the liquid for its lubrication.
therefore you must have positive head on your setup to ensure that the pump impeller is always wet.

4) from a system perspective it will be important NOT to have a manual valve downstream from this pump. it has no internal pressure regulator. it is not a "demand pump" with an intergral pressure switch. closing the shower valve while the linked pump is running will cause peak pump pressure to be attained, the flow rate is of course zero, and then the impeller will be spinning in it's own turbulence. this will overheat the motor, overheat the rubber impeller, and may appreciably shorten the life of the pump.

5) i can't find anything in the PDF that this pump is NSF-approved for potable water. the seal type used at the pump shaft/impeller interface is probably not listed for food use. the impeller rubber itself is probably not listed for food use. something to consider.

6) the addition of a small accumulator tank (pressure tank) may be useful.

see also
http://www.westmarine.com/WestAdvisor/Pressurized-Freshwater-Systems
and
http://www.westmarine.com/buy/shurflo--aqua-king-automatic-pressure-water-pumps--P011_331_002_510

ar-jedi "



So are you saying the pump doesn't work???

I have seen this pump used in many different applications and has worked very well in a variety of situations. Can you describe the usage experience you have had with it?

Regardless of which heater you choose, one option is to mount it on a Metro cart.  I have one that I cut out part of the top shelf and put in a stainless sink.  Then next to the sink I covered the rest of the top with a stainless sheet.  I also have heavy industrial grade poly sheets I can use on top of the stainless sheet for game cleaning so as not to dull my knives, like those roll up cutting boards only thicker.  Propane tank can ride on the bottom shelf and fuel a propane tree connected to a lantern, stove, turkey fryer (beer cooker), hot water heater, whatever.  The sink has two quick disconnects for garden hoses, one to hot, one to cold and sprayer.  I nicknamed it my propane crash cart.

I can use it for cleaning small game, brids and fish, veggies from the garden, brewing beer, outdoor cooking.  I can also roll it in the detached garage or basement for winter use with floor drains.  I am working on a couple of tankless water heater designs of my own that require no electricity, pumps or pressure.  Will work with propane burner or open fire.

There is no substitute for hot water and it is easy to add another 500 or 1000 gallon propane tank.

I think a wood fired boiler or water heater would be a more sustainable long term solution.

My SO opened a valve in the shipping container we live in most of the good months that feeds water to the heater after I had drained it for the winter, either last or the year before.

So it busted the heat exchanger when it froze. The valve issue has been addressed -again...  

They are internally surprisingly high quality, --and serviceable ---if like in our case we have a lot of spare parts from the busted one.

The 2 D cells of course can be bypassed to run on whatever source of 3 volts you have, like a single CR123, for the ignition circuit.

We've never had an issue and the batteries last a long time. Actually I was very impressed when we got the first one about 4 or so years ago. I do keep a spare unit.


We do quick efficient 'showers' to save on precious water, and use about a few gallons at a time.


As far as venting, they burn so little propane, I would have no hesitation to run one indoors in an emergency with suitable precautions.


I run the heater off an RV pump, Shurflow 8009-541-236,  12 volts, 1 GPM, 60 psi, with an automatic demand switch. The same pump provides water for the hand held air nozzle that works as a spray jet to rinse the [no flush] RV toilet.

http://www.ebay.com/itm/380743490761?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT#ht_559wt_1362

Maury makes nice products. That's the one we use, if it is the smallest capacity one.

They are avail I think in propane and natural gas.


We have a dedicated 20 pound propane bottle sitting underneath it and have only filled it a couple times. We don't always use the heater tho, and often go off the mtn for showers, supplies, R&R, etc.