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Thread: Flushing a Tankless Water Heater

  1. #1
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    Flushing a Tankless Water Heater

    My wife and I are not young any more and have to contemplate our mortality. My wife has been bugging me for a while to document how to do some things around the house, such as how to turn the water or gas off in case of an emergency. One other issue was how to flush the tankless water heaters.

    So I put together a number of web pages the document each item, going step-by-step so that she could follow the directions if I wasn't there. Most of the items are specific to our property but I thought the one on flushing the tankless water heater might be of interest to others. The web page is here.

    In case you're not familiar with tankless water heaters, they require annual flushing with a weak acid (vinegar) to remove any build up of mineral deposits on the tubing in the heater. It's not difficult to do, and it's important to efficient operation and long life.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  2. #2
    Thanks for posting this, Mike. We have a Rinnai and I was wondering about the procedure.

    Erik Loza
    Minimax USA

  3. #3
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    Looks good. You may want to document the wrench required to open the valve ports.

  4. #4
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    Thanks Mike, the procedure was documented very well. It is interesting to see the water heater on the outside of the house. Must not get very cold where you are at.

    We have a tankless water heater in a vacation home and I have a plan to install valves to allow flushing the unit. My backup plan is to never flush it in hopes that it will suffer an early death. It is the worst appliance that I have ever owned. It shuts itself off with error messages all the time, including in the middle of a shower. I want to go back to a normal tank style heater that you never have to worry about.

    Steve

  5. #5
    Steve, just curious: What brand is yours?

    We have had zero issues with ours. Great investment, in fact.

    Erik Loza
    Minimax USA

  6. #6
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    Quote Originally Posted by Greg Portland View Post
    Looks good. You may want to document the wrench required to open the valve ports.
    Nothing special. I just use a pair of pliers if they're too tight to turn by hand. I think I said that in the procedure.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  7. #7
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    Quote Originally Posted by Erik Loza View Post
    Steve, just curious: What brand is yours?

    We have had zero issues with ours. Great investment, in fact.

    Erik Loza
    Minimax USA
    Me, too. Never a problem. Mine is a Rheem. I'd never go back to a tank. It's just wonderful to never run out of hot water, and my gas bill went down when I put the tankless in.

    [Side note: When we had a tank, I'd get in the shower and my wife would put stuff in the washer. By the time she went to take her shower, there was no hot water. Unhappy wife! Remember that the secret to happiness is "Happy wife, happy life."]

    Yes, it never freezes around here (southern California).

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  8. #8
    I also have a Rheem (mine made by Paloma) and other than a circuit board that had to be upgraded, which was sent to me with a phone number for an open ended phone call with verbal step by step instructions (phenomenal customer service) I have had zero trouble from the unit itself. The issues I did have were my own. I initially tried to run the heater (rgt53 lp) on two 100lb bottles in a remote home. In cold winters this wasn't enough gas and we would occasionally get error messages I the control panel. Adding a third empty cylinder solved everything.

    I would never go back to a tank type heater either. My only beef with some models can be too high a cut-in flow rate and I do worry sometimes about wear and tear if you live in a house with lots of short cycles (like people who insist on turning both hot and cold on for a quick hand wash when no system other than recirc will get you hot water anyway). But the newer models are amazing.

    We've installed several for customers the latest being a Navien.

    Thanks for the post. I'm iverdue for a flush.

  9. #9
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    Thanks! We have two tankless systems in our home...excellent information to have!
    --

    The most expensive tool is the one you buy "cheaply" and often...

  10. #10
    We had a tankless installed in our last house. It over heated and caught fire. Thankfully I was around when it happened. Cut the power, grabbed the extinguisher but the heat caused the pipe to bust out and it put the fire out for me. Then I had to cut the water off to prevent my laundry closet from flooding even more.

  11. #11
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    Quote Originally Posted by Erik Loza View Post
    Thanks for posting this, Mike. We have a Rinnai and I was wondering about the procedure.

    Erik Loza
    Minimax USA
    I installed a Rinnai about 4-5 years ago, and love it.. Mine came with bypass flushing valves. We are on a lake based water supply, and about the only thing in it is added chlorine. I did have a oil fired water heater that was very fast (54deg-130 shut off in 17 minutes), but it burned $600.00 worth of oil a year. The Rinnai uses 14 cents worth of N.Gas a day ($51.00 a year) Showers/dishwasher/etc..e. Lake water is very soft, and we don't even get a mineral deposit of anykind on anything. So, I have not had to flush it at all.. I don't know why anyone would want to keep 40-50 gallons of water constantly hot in case you need it..
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  12. #12
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    Quote Originally Posted by Erik Loza View Post
    Steve, just curious: What brand is yours?

    We have had zero issues with ours. Great investment, in fact.

    Erik Loza
    Minimax USA
    It is a Bosch AquaStar 250SX. The reviews are not very good. It appears that people either love tankless water heaters or they hate them. I am in the second group, but maybe it is just this brand.

    I cannot think of a single characteristic (except small size) where it performs better than a tank style heater. I don't believe that there is a cost savings after taking into account the extra upfront cost. We cannot use a low flow showerhead because it doesn't use enough water for the flow detector, so the only option is a less efficient showerhead. Two showers and a dishwasher running at the same time will produce lukewarm water. And it is nearly impossible to maintain a comfortable shower temperature. It switches from too hot to too cold, so you have to constantly adjust the temperature.

    I miss the old fashioned tank style water heater.

    Steve

  13. #13
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    Quote Originally Posted by Steve Peterson View Post
    It is a Bosch AquaStar 250SX. The reviews are not very good. It appears that people either love tankless water heaters or they hate them. I am in the second group, but maybe it is just this brand.

    I cannot think of a single characteristic (except small size) where it performs better than a tank style heater. I don't believe that there is a cost savings after taking into account the extra upfront cost. We cannot use a low flow showerhead because it doesn't use enough water for the flow detector, so the only option is a less efficient showerhead. Two showers and a dishwasher running at the same time will produce lukewarm water. And it is nearly impossible to maintain a comfortable shower temperature. It switches from too hot to too cold, so you have to constantly adjust the temperature.

    I miss the old fashioned tank style water heater.

    Steve
    If my tankless did all that, I'd hate it too. The Rheem heats water at a pretty low flow. I shave with a low flow of hot water and I'm the only user on the system and I get constant hot water. I have a low flow shower head (I guess everyone in CA has those) and have no problems with constant temperature water.

    Tankless is an old technology - you'd think all the manufacturers would have worked out the bugs by now.

    Regarding two showers and a dishwasher running at the same time and the tankless not being able to keep up - tankless heaters are made with different maximum flow rates. If you draw more gallons per minute (GPM) than the tankless is rated for, you will not get constant hot water. You have to size the tankless to the expected maximum flow.

    I agree that the cost to switch is high - I had to reroute plumbing and add an electrical circuit. But I wanted to recover the space used by my tank style hot water heater. I may, or may not, ever recover that up front cost, but I'm glad I made the switch. My tankless works well and I like never running out of hot water.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  14. #14
    I realized my question may be considered as highjacking this thread so I deleted it.
    Last edited by ken masoumi; 02-09-2014 at 11:18 AM.

  15. #15
    Quote Originally Posted by Steve Peterson View Post
    It is a Bosch AquaStar 250SX. The reviews are not very good. It appears that people either love tankless water heaters or they hate them. I am in the second group, but maybe it is just this brand.

    I cannot think of a single characteristic (except small size) where it performs better than a tank style heater. I don't believe that there is a cost savings after taking into account the extra upfront cost. We cannot use a low flow showerhead because it doesn't use enough water for the flow detector, so the only option is a less efficient showerhead. Two showers and a dishwasher running at the same time will produce lukewarm water. And it is nearly impossible to maintain a comfortable shower temperature. It switches from too hot to too cold, so you have to constantly adjust the temperature.

    I miss the old fashioned tank style water heater.

    Steve
    Wow, what a bummer. I am sorry to hear all that because, to be honest, ours has improved the hot water situation in the house at all levels. We have a walk-in shower upstairs with two heads. Wife and I can shower for as long as we like and no hot water issues. I routinely run the dish washer and the washing machine at the same time, no issues there either.

    Two things I will say, though:

    1.) The unit we bought was rated slightly higher than we thought we would ever need in terms of BTU's. Figured "Why not?".
    2.) We have no water pressure issues on the supply side. The City tore up our neighborhood and replaced all the old iron pipe with new stuff. And when we remodeled the house, I had every piece of galvanized pipe replaced with PEX, so there are no flow issues on the suplly side.

    No idea if either of those are/might be a factor in your case but I can tell you that there is nothing not to like about the technology, itself. Just my 2-cents as always.

    Erik Loza
    Minimax USA

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