Which tankless water heater is best

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by gkuhrt, Jul 28, 2005.

  1. gkuhrt

    gkuhrt New Member

    Messages:
    3
    Location:
    Canada
    I can't find ratings for tankless water heaters. I can find comparisons but nothing to indicate which units are better/more reliable/common problems. I hope this is the last water heater I buy and I want to end up with a good unit and not a lemon.

    Any tips/advice/recommendations would be greatly appreciated!
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,325
    Location:
    New England
    Do a search (menu at the top) on tankless and you'll get some opinions. This subject comes up fairly frequently. While they can save energy costs, their much higher initial cost and maintenance hassles is likely to make a tank type better. The flow restrictions and (if you live where the ground water gets really cold in the winter) other considerations can really affect overall satisfaction.
  3. SteveW

    SteveW DIY Senior Member

    Messages:
    1,054
    Location:
    Omaha, NE
    I completely agree with Jim. When you do the search, you'll see a lively debate on this topic. I had been thinking that when my water heaters finally gave up the ghost, I'd convert to tankless, but the well-reasoned comments on this site convinced me that this is still too young a technology for me to be comfortable with it. When one of mine did start leaking a couple months ago, I replaced it with a conventional tank unit.

    Now, maybe in 10 years, who knows?
  4. slb

    slb New Member

    Messages:
    48
    Location:
    San Francisco North Bay
    For what it's worth, my brother has had a tankless water heater (I don't know the brand) for four years now and has had no problems. He has a family of five and they were always running out of hot water with a conventional tank heater. The "endless hot water supply" was the main factor in his decision. According to him, it's never a problem anymore.

    -Steve
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,325
    Location:
    New England
    A couple of potential gotchas. The intense heat causes minerals to precipitate out of the water and potentially coat the heating coil. This can decrease the capability of the system drastically. Cleaning it out is a pain. They can only raise the temperature a finite amount. Think waving your hand through a candle flame. The slower you do it, the hotter your hand gets. Now, make it a blowtorch, you can still do it if you are fast enough without burning your hand. In the winter, your incoming water temp can get quite cold. It may be marginal in some locals. Now, if you live in Florida, or say southern Arizona, it won't be a problem; in Minnesota it might. Depending on the size, you might not like the reduced flow. It can be a real problem if someone else turns on hot water while you are taking a shower. More water, less temp rise, cold hit in the shower. So, hopefully, you can live with this; I gave up. During the summer, I like mine, during the winter, I hate it; but, I'm the only one in the house. I do NOT like the decreased pressure and volume anytime. Don't have the washing machine or dishwasher come on while you are taking a shower, you won't like it! Also, assuming it is a gas fired unit, ensure you have outside air - you need a significant amount. If electrical, you might have to upgrade your electrical service. The higher the volume you need, the amount of heat needed rises radically. Consider that all that temp rise needs to occur in only a few feet of tubing - really concentrated heat.
  6. Cal

    Cal New Member

    Messages:
    228
    Location:
    Northern Virginia
    If you are serious about an GREAT tankless,check out the Rinnai .

    Have installed several of them on "Pop top" additions ( 3 baths each) and have gotten wonderful feed back from the customers.Rinnai does it right,good volume,easy installation,very easy maintaining the units. We are in No.Va. so our climate issues are not that of more northern states,,,,temp settings are pretty well maintained .
    Cal
  7. Cal

    Cal New Member

    Messages:
    228
    Location:
    Northern Virginia
    You mean,,,JUST LIKE A TANK TYPE ? So we SHOULDN'T try anything new?

    Have you tried them or just let a website decide what's best ?
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,325
    Location:
    New England
    A typical tankless system is designed to raise the incoming water 70 degrees (farenheit) at it's design max flow rate. If you aren't using the max flow, there is typically a mixing valve on the output to temper that (now) hotter water. The tempering valves fail, and then you can have VERY hot water come out of the thing. Because they produce intense heat to be able to raise that temperature so fast, they need significant heat source. They come in both electrical and gas-fired versions. Either one may stress the typical supply source, if not already sized for them. On gas-fired ones, many people don't consider the make-up air requirements. One of these things is like adding another full-sized gas-fired furnace. Now, many of those are now using closed combustion with a piped outside air source. BUT, not all. Then, consider if you have a gas-fire dryer in the house. If all of them are running at the same time, you need huge amounts of fresh air to come into the house. So, that that into consideration. Say you have a system rated at 4 gallons/minute. That is 32 pounds of water. You want to raise that 70 degrees. That's 32*70*60 = 134,400BTU. That's a significant amount of burning. Also, now that that thing that can only flow 4 gallons/minute. You have a 40 gallon tub; it will take 10-minutes to fill the tub. Also, now run two showers at the same time - typically 2.5*2=5 gallons/minute. Now, your heater flows a max of 4, guess what - low flow, unsatisfying shower for both participants. Maybe it's not two showers, but one multihead job. It quickly gets pathetic. A tank type needs to be sized properly and have a quick enough recovery to satisfy your max needs, or again you will have compromises. But, you will get the max flow possible by your plumbing, with no restrictions by the heat source while you want it. A good tank, well insulated is very simple - the surface temperatures of the heat exchanger do not get as hot, so you don't get as much mineral deposits. Having soft water helps the life of either type, but is much more a factor with a tankless. I'm not particularly impressed with mine. I'm going to update not only my boiler but replace the hot water with an indirect heater. A small, 40-gallon tank on this system is rated at 150 gallons or so of hot water an hour. That's one shower running continuously; plus, when you want to fill the tub, you don't have to wait, either. Look carefully at the max input - not all of that input gets transferred to the water, so in my example above, at say 90% efficiency, the actual input would be 149,333 BTU or 43.725Kw (190Ahr) at 230vac. Like I said earlier, you need significant energy available to heat that water "instantaneously". Look carefully at the specs. Storing some water allows you to buffer that use, and makes that supply problem go away. A bigger tank, and or one with a faster recovery rate is still cheaper to install than a tankless, and over its life will cost less with fewer hassles. My unprofessional opinion.
  9. MikeAmico

    MikeAmico New Member

    Messages:
    2
    tankless is not a new technology

    Gkuhrt,
    Tankless water heaters is not a NEW technology. Its just that we in North America are way behind the curve. They've been using tankless in Europe and Asia for many, many years. I used them in Tokyo in 1981 and they were not new back then. They are just more efficient because of their concern with conserving natural resources. You go to England, for example, and you'll see them everywhere.
    The Takagi which is what I'm installing can be put outside without a cover. It's built that strong. It's not cheap but worth it. Good Luck.
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,325
    Location:
    New England
    Tankless has improved significantly overthe years. I was not impressed with one in a house I rented in Germany 25 years ago, or with the one I've had in my house. I'm sure the new ones are better, and in the right circumstances acceptable, but, they have their limitations. If you can live with them, then fine, but you need to recognize them. While running costs are lower, they aren't as low as many people think. Depending on how much water you use, and the schedule you use it, the standby losses of a quality well-insulated tank is not much. The indirect fired tank I'm probably going to use has 1/2 degree per hour. Basically, once you get it hot, it probably won't need to run again before you draw some hot water off, causing it to refire to bring the overall tank temp up to the setting. This is a far cry from low-end, poorly insulated tanks. Basically, almost no standby losses for practical purposes. So, for a tankless, you get a more expensive system, harder to fix when it does need it (hopefully not too often), depending on your water quality and hardness, more maintenance required, and less likely to have parts or a qualified person to service it when it does need it.
  11. CAL.... go for it buddy

    CAL, I have never installed a tankless water heater

    but I have torn out plenty of tankless heaters ......

    their are a lot of things new and old out there

    that are probably best left alone.

    just from observation it appears that they are about 5 times more
    expensive and not as reliable

    here are some links for ya to chew on

    http://www.askthebuilder.com/451_Tankless_Water_Heaters_-_Some_Surprising_Facts.shtml


    http://www.google.com/search?hl=en&q=tank vs tankless water heater efficiencies

    -------------------------------------------------------
    dont take my word for it...go out there and get yourself one.
    ---------------------------------------------------------
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