Advice - Tankless Water Heaters !

Discussion in 'Tankless Water Heater Forum' started by sandy2982, Mar 27, 2008.

  1. sandy2982

    sandy2982 New Member

    Hi ,

    I finally decided to replace the water heater I have with a tankless one. After some research, I narrowed the choices down to two "finalists": Takagi and Rinnai tankless water heaters. Rinnai seems to have some advantages, among them higher output (8.3gpm vs. Takagi's 6.9gmp) and, most important, lower kick-off flow (0.5gpm vs. Takagi's 0.75gmp). On the other hand Takagi seems more spread than Rinnai and also I could find a lot of information for Takagi and almost none for Rinnai.

    Need some advice from people who are using these water heaters.
  2. Cass

    Cass Plumber

    What is your incoming water temp in the winter, what is the hardness of your water, what is the max. temperature rise of the units, will you have enough gas flow to the unit with your existing piping, where are you venting it.
  3. jimbo

    jimbo Plumber

    San Diego
    At what temperature rise are those gpm numbers spec'd? Huge difference if it is at 40º or 90º. Also, do you know what it will cost you to install the required large gas supply pipe, and the new larger STAINLESS STEEL flue.?
  4. hj

    hj Moderator & Master Plumber Staff Member

    Cave Creek, Arizona

    Or even the same sized stainless steel flue. If you are going to do it yourself, you may have to scratch the Rinnai, because they are only supposed to be sold to certified installers.
  5. Gary Swart

    Gary Swart In the Trades

    Yakima WA
    Seems like the idea of tankless water heaters comes up about 2 or 3 times every month. It sounds great doesn't it. Just heat water when you need it and don't pay to keep a tank of water hot when it's not needed. A really money saver! Wow, it's about time! Only thing is, after all is said and done, these things cost more to own and operate than conventional water heaters over a period of time. Here are some of the pitfalls. High initial cost of the unit; high installation costs, including larger gas or electric service; frequent repairman calls to clean the innards and keep the thing operating, if you can find a repairman; limited hot water output in cold weather; high operation cost; and finally, they don't last forever and when replacement is needed, the circle of life begins again.
  6. robertsmu

    robertsmu New Member

  7. Interesting what happens over time

    its funny how you hear more and more about people
    wanting the tankless units and the people
    who complain about them after they own them

    over time it simply has to fail
    its just a matter of when. and how soon......

    just like the last thread where the 2 year old Takagi went down and
    the home owner jury rigged up his own repairs for it.....

    going green is a fad that should not spread to things as complicated and
    expensive as these are

    I just had a homeowner
    today calling about the tankless units at about 12.30,
    but before I could get back to him -- having a Friday power lunch---
    he had gone to LOWES and now is
    hell-bent hooked on a Bosch....

    took the bait ....hook, line and sinker......

    I wont be able to talk him out of it no matter what I try to tell him....

    Hell, I just do this for a living,,
    the guy at LOWES is the expert.
    Last edited: Mar 28, 2008
  8. srdenny

    srdenny Plumbing Contractor

    SF Peninsula
    In a situation where a tankless heater can be mounted on an outside wall, near the gas meter as well as the fixtures served, where the winter climate is mild and the water is of good quality, then a tankless heater makes sense, especially for a guest or vacation house that's often vacant. Here's a site that has a lot of information:
  9. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Central Florida
    And both of them need a lot more practice using the TelePrompter...
  10. SourKraut

    SourKraut New Member

    Long Guyland, New Yawk
    I'm curious if this technology is just a fad that it only" here in America do we know how to heat water". yet the systems have been used and PROVEN to work for over seventy years!. But what do those yurupeans know, why this is the land we can can make a car last as long as the payments before things start to fail. Maybe the failures we have over here are ignorant installers putting it in the way they think it should be installed instead of how it was designed to be by the manufacturer.
    If it's a problem with the water then it's a problem for everything regardless the technology.
    "green" is not a fad, it's a social responsibility to make things operate as efficiently as possible always. The "good enough" attitude is partially the reason why we're paying $110/barrel for oil now. They know we need it.

    Just my opinion from a little piece of suburban heaven.;)
  11. my Green tankless water heater

    When they can get the price down to about

    the cost of what a normal water heater costs

    then I will get one even though the install costs
    will still be higher...

    then you might break even in 10 years or so

    I am still haggleing with supply houses for a
    decent deal on a tankless heater right now
    to keep going with my own little experiment


    here is a pic of my "green tankless heater"
    the unit was installed in 1910 ..the reason
    the tank type heaters took over in the 20s and 30 was the fact that
    these were too complicated and too much touble even back then
    and people were constantly blowing them up..

    they thought that they had made a giant leap forward
    when the first tank type heaters came out with
    the internal thermostats...getting away from all these
    high pressure issues and valves that had to be manually
    controlled to get hot water..

    I believe that this was called a "side arm" heater..

    Last edited: Mar 29, 2008
  12. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Central Florida
    If you want green, go solar. I'm in a good part of the country (Florida), at a mediocre time of year (a week past the equinox) with a poorly oriented and shaded (by a neighbor's oak tree) collector, but at 6PM yesterday I had 80 gallons of 150 degree water in the tank after a normal day's usage. I installed the system a little over a year ago, in the dead of winter, and inadvertantly left the circuit breaker for the water heater (backup electric heating) off. It was about 3 weeks before we noticed the water cooling off. I won't know the true cost until the tank eventually fails, but the net outlay was about $3000 for the professionally installed system, and I only had to redo a small part of it. DIY kits are available for about $2200; more (~$5000) for a "hard freeze" area.

    My main concern now is -- how hot will it get, after a full day in the summer sun?
  13. robertsmu

    robertsmu New Member

    Tankless heaters are def more complex than traditional heaters, will require regular maintenance, and are more expensive to install, but they probably won't cause the problem that I am now fixing: water damage caused by a leaking water heater.

    The heater before this unit must have leaked as well, because the whole structure underneath is rotted beyond repair. Complete replacement of all joists and subfloor. Insects in Texas love moist wood. Need I say more?

    In my application (just a washing machine, kitchen sink, and dishwasher) tankless (Bosch 1600) will suffice. Cost only $300 after uncle sam chimed in.

    I'm willing to give it a chance.
  14. it can get hotter than hell

    do you have a system with some sort
    of antifreeze in it that will not boil???

    if you are useing a water type drain down system
    those puppies can literally boil the water in no time...
    if the recirulaitoin pump were to fail

    On our summer vacatioin in florida last summer it was 98 degrees at disney land for the whole week....

    (it made the battan death march look like childs play)

    really all you need to do in Florida is put about 2500 feet of
    3/4 wirsbo pex in your attic feeding your hot water heater
    and I can guarantee that you would probably never run out of hot water.....
  15. adb

    adb New Member

    IMO the best means of on-demand tankless water heating is via a dedicated domestic coil in a heating boiler. Absent that, get a properly sized high-efficiency tank from BW and call it a day.
  16. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Central Florida
    Bubble, bubble, boil and trouble

    No, it's a straight all-water system -- an extra inlet/outlet pair in the storage tank. There's no control system at all -- just a PV panel to generate the 12V to run the pump. Simple and elegant -- no sun, no heat, no pump -- but as an engineer, I'd like some dials and knobs. We made it through last summer with no apparent problems, but God knows how hot things got -- I'll find out this summer. I'm on a well with a bladder tank, so there's no overpressure problem, but I'll be testing the temperature limit of the CPVC (ASTM rated for continuous service at 100 psi and 180 degrees F; for ½†through 6†pipe, the limit is 239°F/115°C).

    As for coils in attics and heating boilers, I thought about that (the attic, anyway), but even Florida has some mighty cold nights, and I've only seen 130F in the attic in the summer. After my next re-roof, that should drop significantly; in Florida, the objective is to keep as much heat outside the house as possible.
    Last edited: Mar 30, 2008
  17. Cass

    Cass Plumber

    Had there been a drip pan installed... there would have been no damage.
  18. Cant Tankless water heaters leak too????

    It amazes me how many people will opt not to get
    a 15 dollar pan put under their new heater..
    and then when they have a good flood or just a
    very slow un-dectable leak that does tons of damage
    they still are too damn cheap to get a pan for their new one...

    water heaters dont flood people out...
    people flood themselves out by being cheap tightwads.
  19. srdenny

    srdenny Plumbing Contractor

    SF Peninsula
  20. robertsmu

    robertsmu New Member

    Sure, had the drip pan been installed 35 years ago!! The heater that recently failed didn't drop its water. There was decades of damage there, my friends.

    When I replaced the water heater on the other side of my house a couple of years ago, I put a drip pan under that one. All nice and pretty.

    The point is, and we are off track here, that tankless heaters for all their shortcomings, won't cause that kind of long-term damage.
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