On demand water heater.

Lefty WrightLefty Wright Solar Expert Posts: 111 ✭✭
A neighbor built a new house and wanted to install an on demand water heater. But his permit application was denied by the county building department.

They said our water is too cold for on demand heaters for work here.

We are in an off grid community and everyone has a well for their domestic water.

Since we are off grid everyone has a water storage tank instead of pumping directly into pressure tanks like on-grid folks can do. So I doubt that the temperature of the water in the well has anything to do with the water temperature seen by the heater.

This sounds crazy to me. Can someone who knows more about on demand heaters shed any light?


  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: On demand water heater.


    I use the smallest Paloma demand water heater,,,~PH6. It takes lake water out of the frozen lake in the dead of winter @34f and heats it too hot for a shower @43,000 btu/hour. That at ~1.0 gpm. Larger models go over 100,000 btu. In a rental house we have a Takagi Tk Jr that burns ~140,000 btus. It will put out 100f rise at 5 gpm.

    Takagi, Rinnai, Noritz, and Paloma all make electronic control models that will temper the outgoing water to a predetermined temp. They all make bigger models for higher demand such as car washes , laundamatts, and big McMansions.

    I suggest you look carefully at the UBC or the UPC and you will find no such prohibition. I will do some looking later, but I have never heard of such a thing. ( a quick google search reveals tons of code acceptance information: CODE ACCEPTANCE Water heating equipment is covered by the 2003 International Residential Code in Chapter 28 - Water Heaters, Chapter 20 - Water Heaters, and Chapter 24 - Gas Water Heaters. I don't have a current copy of the UBC or UPC.

    Fight the building dept. The reality is they are denying something that they know nothing about. Submit the listing for the proposed heater, (available on line) UL CE, UPC. Drown them in paper and perhaps they will see the light. The only code issue I have ever run into is providing enough combustion air. Many units are sealed combustion so that they draw outside air, and vent to atmosphere.


    PS Most well water comes out at~ 50f. Most city water in northern climes is about the same temp.
  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: On demand water heater.

    Blowtorch on a coil of copper pipe. Run the water slowly, and you get very hot water.
    Run it fast enough for a shower, and you get tepid water.

    Perhaps, if you use a solar water heater, and feed the on-demand heater the preheated water, they will accept that. If you have 2, 50 gallon tanks of tepid or even hot water, from solar heat, that would supply acceptably warm water to the on-demand heater.

    Also, look into a "Tempering tank" just a storage tank, to let the water come to room temp.
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  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: On demand water heater.


    Read my edited post below yours. There are many models of demand water heaters that will put out way more than any domestic well pump could deliver.


    This Takagi at 64f temp rise will deliver 6.5 gpm! There are other brands out there that will do more. Regardless of the flow rate, there is a heater that will suffice, regardless of whether you can (or do) preheat the water.

    Demand water heaters get a bad rap because people don't understand them.

  • Lefty WrightLefty Wright Solar Expert Posts: 111 ✭✭
    Re: On demand water heater.

    Just as I thought, Guys. The building department is nuts.

    I'm in a county of less than 50,000 people and only 6 stop lights.

    When I built my garage the building department told me they required a 4X28 inch header over the 16' garage door. That meant I couldn't have a 7' high door.

    After I went crazy and demanded my money back for the building permit they relented and said, Oh yeah, you only need a 4X14.

    I was going to build with steel studs but they didn't know what they were. So it's not surprising that they are screwed up over water heaters.
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: On demand water heater.


    I would take the listing sheets from the brand you wish to use, or barring that, as forgiveness rather than permission. I will work on finding the proper UBC/UPC chapters and verse. It might take a few days as all my books are out of date. Where are you located? Find out what code they use, and then we can find chapter and verse on that code. Assuming the jurisdiction has adopted some standards, they can't not let you use it. Another suggestion, although one that will cost you a nickel, but you could hire a PE to write an report. A stupic waste of money. Perhaps if you have plumbers licensing in your area you could enlist a licensed plumber to go to bat for you in trade for getting it through the building dept.

    I was a builder for 25 years, and a ICBO certified inspector for a few years. If the owner/builder was reasonable and could prove the listing for a device, then there was never any question.

    Good luck and let us know how it goes.

  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: On demand water heater.

    I just talked to a plumber friend of mine. He says that the International Mechanical code for plumbing and gas has no such prohibition. He did warn that an electric demand water heater might present a problem because of the shear number of amps required. He has installed 380k Rinnai units in many resturants, health clubs and the like. As I suggested, they just need to be sized properly for the incoming temp/expected flow rate.

  • BrockBrock Solar Expert Posts: 639 ✭✭✭✭
    Re: On demand water heater.

    Or kill two birds with one stone. Just buy a 40 gallon electric water heater to put in front of the demand water heater. Then wire it all up nice pretty and once they leave turn it off. That will make them happy and you have a 40 gallon "preheat" tank. If your pumping to a "holding" tank and then to the home that is technically doing the same thing.

    The other advantage of an electric pre heat tank is you could eventually plumb it up to a solar hot water or geothermal or even use it to dump excess solar electricity, if there were any.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • Lefty WrightLefty Wright Solar Expert Posts: 111 ✭✭
    Re: On demand water heater.

    Right now I use a propane fired tank heater. When I built my place the on-demand water heaters were not common.

    This summer I intend to upgrade and them I'll use the tank heater for a pre-heat reservoir after piping the feed water through my woodstove.

    That's what most folks do around here.

    The local county building department is pretty much a joke. The first thing I built was a garage and I included a bathroom in it.

    When the inspector came he found that I had not taken out a permit for a dwelling. He told me I couldn't have a bathroom in the garage until I built a house!

    When I asked him how I was supposed to put the plumbing under the garage slab after the house was built he said,"Oh yeah. Go ahead and install the pipe but don't hook up to the utility until after your house is finished."

    Hook up to the Utility??? I'm 10 miles from the nearest power line so I guess that I'm the utility. By the time the inspector got to his next job I had the water running in my illegal bathroom.

    The down side of having out-of-touch-with-the-modern-world people running the local government is that they discourage any progressive innovation in construction.
  • DagoRanchDagoRanch Registered Users Posts: 8
    Re: On demand water heater.
    The down side of having out-of-touch-with-the-modern-world people running the local government is that they discourage any progressive innovation in construction.

    And that's when you nod and go "yup" and do what you're going to do ;)
  • System2System2 Posts: 6,290 admin
    Re: On demand water heater.

    Re: Tankless water heaters. Consumer reports has an excellent and very informative report in their October 2008 edition, starting on page 28.
    Anyone who has never had such a heater, should really study this report. You'll then know the pros and cons of both gas and electric, tank and tankless, before making your decision. There are some very important issues to consider.
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: On demand water heater.

    No offense Wayne, but I found the CR article on water heater full of misinformation. The worst was the estimated cost of installation vs a conventional water heater, somewhere in the neighborhood of over $1000 more for a a demand if memory serves.

    The truth is that demand water can cost more (even substantially more) to install than a conventional "B" vent gas tank type, but, if the design is thought out and the heater located in a good spot, the venting can be quite cheap. If you can locate the heater on an outside wall, the heater can direct vent out the side wall with a simple vent hood kit. If you can vent strait up through an short attic space with a simple vertical run it can be reasonable as well. If you have to do a bunch of twisting and turning it can indeed get expensive. ( This assumes a direct vent/power vented unit that vents through a Stainless steel vent. Older types, (some bosch, Paloma legacy series) vent through conventional "B" vent, just like a conventional tank water heater).

    Also, gas piping size has to be allowed for, since the per hour btu rating of the heater is much greater than the piping for a conventional. (I have found that gas piping sizes are very conservative, and they can assume that all the appliance on a branch will be running at once). It is also possible to run the gas line with higher pressure (to reduce friction losses) and then regulate down to proper pressure at or near the appliance.

    With the advent of pex piping, and flexible indoor gas piping, as well as the compact size of the units, relocating the units to a better spot is often quite feasible.

    As to the permit issue, you can find a used electric ($10-25 on Craigslist), plumb it in as a preheat tank, wire if needed, then kill the breaker.

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