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Reuben Saltzman

Tankless Water Heaters – A Few More Things to Consider

In last week’s blog post, I discussed the amount of money I might save by having a tankless water heater installed, and I concluded that I would never see a return on my investment.  I received a lot of good feedback from that post, both for and against tankless water heaters.  I thought it would be worth bringing up a few few of these points in another post.

Pros

  • You can’t put a price tag on going green.  There’s no dispute about this – tankless water heaters use less energy.  Doing the environmentally responsible thing doesn’t always have a measurable return on investment.  I mentioned this last week, but only briefly.   Not everything we spend money on will give us a return on our investment – we all know that.   After all, what’s the payback period on a sofa?
  • Tankless water heaters make sense for a cabin / vacation home.  Traditional water heaters have a ‘vacation’ setting, but I’ve heard it’s a bad idea to use this setting, because it greatly increases the potential for legionella pneumophila growth.   Having a tankless water heater installed in one of these settings would result in much more than a 25% fuel savings.
  • Energy Star Tax Credit.  This $300 tax credit which includes tankless water heaters, expires December 31, 2011.   You can read about it here – tax credit.  I’m guessing we’ll see another one show up when this one ends.
  • Fuel costs will continue to rise.  As we all know, fuel costs continually increase.  If fuel costs tripled in the next 20 years at a linear rate, a tankless water heater would actually give me a return on my investment, using the numbers from the example last week.

Cons

  • Low water flow = no hot water.  If there isn’t enough hot water flow, a tankless water heater just won’t turn on.  One person even commented that they had to turn on the hot water faucet at their bathroom sink and leave it on the entire time they took a shower, or they couldn’t get hot water.  For instance, Rinnai tankless water heaters need at least .6 gallons per minute, Bosch units need .65 gallons per minute, and Rheem at least .4 gallons per minute of hot water flow to kick on.
  • The cold water sandwich.  If you think gefilte fish sandwiches sound bad, just try one of these.  The cold water sandwich effect is something that happens with every tankless water heater.  When the faucet is turned on, off, and on again, you’ll end up with a slug of cold water interrupting your hot water flow.  Some tankless water heaters require the call for hot water to last for at least three seconds before the burners turn on, so there can be several layers of hot and cold water in the pipes.  This doesn’t exist with traditional water heaters.  You can read more about this at Rinnai’s web site – they claim to have nearly eliminated the cold water sandwich, but not completely.
  • The long wait for hot water.  I already have to wait for approximately forever to get hot water at my kitchen sink, but the wait would be even longer with a tankless water heater.  One interesting solution that I heard a plumber mention was to install a dedicated 3/8″ supply line to his kitchen sink from the water heater.   He claimed that this still provided just as much water flow, and made the wait much shorter.  I’ve considered doing this at my own house, although this is technically a code violation.

For me, a tankless water heater doesn’t make sense just yet.  I’m waiting for the price gap between tankless water heaters and standard water heaters to get a little smaller.  I have the temperature cranked up on my water heater with a tempering valve installed, so I never run out of hot water.  Maybe by the time my kids are teenagers I’ll have a different opinion of tankless water heaters.

Reuben Saltzman, Structure Tech Home Inspections – Email – Home Inspector Minneapolis

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No responses to “Tankless Water Heaters – A Few More Things to Consider”

  1. Paul Futcher
    November 3, 2011, 8:52 am

    Thank you for the additional considerations in your comments about tankless water heaters. I use an electric unit at our hobby farm in Wisconsin. It pulls 60 amps when operating. My ENTIRE electric bill (I no longer use propane or wood and there is no natural gas there) including heating my home & shop, as well as running my large aircompressor etc averages 35 dollars per month. I am serious. I heat my rooms as necessary to keep the pipes from freezing during winter. I use an new electric range. My water is hot within seconds, & I have been known to take long showers. Lastly, I installed the plumbing & the wiring to this simple tankless heater myself. Pennies on the dollar, for my situation anyway.

  2. Mike Dodge
    November 12, 2011, 8:40 am

    Tankless water heaters use just as much water as a tanked water heater. To be really green, the user should not take long showers. In fact, a real greenie should shower like submariners do. A short burst of water to wet the body down, soap up and follow with another burst of water to rinse the soap off. The water should flow for less that a minute total. Very little water and heat gets used.

  3. Chris
    February 28, 2012, 4:04 pm

    I purchased a tankless ELECTRIC water heater. While I loved it when it works, it is a maintenance nightmare. The designers chose to use ultra high density heating elements, to keep it small. VERY BAD idea if you have ANY minerals in your water. I have to dissasemble mine about every 90 days and usually replace at least 1 of the 3 elements, because they are so encased in calcium & lime that they are impossible to remove.
    Because the flow is so restricted the build up has no way to escape, and eventually destroys the elements. I even sent mine back to the manufacturer who rebuilt it, and it lasted roughly another 90 days. I have no doubt that I could build a better one myself, the idea is awesome. But any tankless electric water heater that is built to last will require a physical size much larger that the shoebox sized ones some people sell.
    Look for one that uses LOW Density elements, if you want it to last. Or maybe a design where the elements are not in the water, but around the pipe.
    Hope you have better luck than I did.

  4. steve Aube
    July 3, 2012, 10:22 am

    WE are in the process of trying to figure out which heater to use, we have an electric tank and it is old and we are redoing the house. The well water is so cold we removed all the pipes from the ceiling and ran them under the crawl space with Pex. we live in new England which heater would you put in if it was your house. 1 and 1/2 bath 3br lake house full time occupancy.
    Thanks for any help you can give
    Steve

  5. Reuben Saltzman
    July 3, 2012, 2:05 pm

    Hi Steve,

    Did your electric tank give you enough hot water? If so, your best option would probably be to replace it with the same thing.

  6. Anthony
    December 20, 2012, 11:38 pm

    This is really good..

  7. Lisa
    December 28, 2012, 4:57 pm

    Can you give pro/cons of installing tankless in an attic. Read where that is a solution. Live in southern california so freezing not an issue.

  8. Reuben Saltzman
    December 29, 2012, 8:10 am

    Hi Lisa,

    I’ve never even heard of a water heater being installed in an attic. I don’t have any experience with that, so I wouldn’t be a good source of information.

  9. Sanders
    January 16, 2013, 7:19 am

    I am planning to get a tank less water heater. If anyone can suggest me the best and cost effective water heater for me??

  10. Rudy F
    January 19, 2013, 1:17 pm

    Hi All….
    I bought a tankless water heater by rannai and i am so dissatified with it i want to throw it out…it has been a piece of garbage since day 1…i dont get any hot water i mean hot water for about 45 mins…i have to wash my hands in cold water and it feels im living in the days of the out house when plumbing wasnt plumbing…i dont save anything on it …i have to turn the damn thing up to 140 to get anything remotely hot…this has been one nightmare and now the company who sold it to me doesnt want to do anything at all about it at all…i wished i had did a little more research before i bought $2400.00 worth of trouble…i am so mad at these people for lying to me and saying it was a good thing to have one of them…if you are there reading this and considering buying one of these….DONT !!!…..you will be sorry !!!

  11. kitchen hand (paul kennedy)
    February 27, 2013, 7:29 pm

    I am lucky enough to have a Vaillant continuous flow HWS which works superbly. It was already installed when we bought the house and dates to approximately 1970s. It was built in Germany.

  12. Karen
    June 20, 2013, 8:02 pm

    For the cost of a tankless plus maintenance, I wish I never got one. I am paying $400 now for a new flow sensor and labor cost. I want to cry. A regular tank does not require all this extra cost, whereas a tankless is very complex, just like a car.

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