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Thread: DIY annual vinegar flush--how much pump?

  1. #1
    DIY Senior Member guy48065's Avatar
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    Default DIY annual vinegar flush--how much pump?

    My question is how much volume is needed to flush the heat exchanger? Is it necessary to use a big submersible 1200GPH pump like I've seen on Youtube--or would a smaller system using maybe a 80GPH condensate pump do the job? The condensate pump or a cutting fluid tank/pump from a lathe would make a nice system.

    Is it the chemical that's doing the work--or the turbulence of a high-volume pump knocking the crud off?
    Romeo and Atlanta, MI

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    Retired Defense Industry Engineer jadnashua's Avatar
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    The acid dissolves the water soluble mineral deposits...super high velocity isn't required or desired. You do need a pump that won't be destroyed by the (mild) acid, though. My unprofessional opinion...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member Reach4's Avatar
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    I suggest you do a search for "phosphoric acid" scale "on demand" " water heaters".

    I am no expert, but I would use diluted phosphoric for that. It is not poison when diluted. It is even used as a food additive. I expect it to be much more effective than vinegar. One advantage to vinegar is that it comes pre-diluted, so you cannot get that wrong.

    I used phosphoric acid to clean an old water heater to get stuff out. I also used liquid laundry detergent next. Then I put an electrical protective anode into that water heater. I also installed a nice filter that has stopped the black and red stuff from forming. Phosphoric acid is available at Home Depot in a place not related to plumbing or cleaning. Klean-Strip Phosphoric Prep Etch. Very strong. I can't tell you how much to dilute it, so you could buy a pre-mix. http://www.speedclean.com/products/t...intenance.aspx

    Don't rely on me. Do your own study. The fact that I did it does not make it right.

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    DIY Senior Member guy48065's Avatar
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    Let me ask it this way...most people pay a pro to do this job. What pump do the pros use?
    Romeo and Atlanta, MI

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    Master Plumber kcplumber's Avatar
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    We do lots of water heaters but rarely get a call to service a tankless water heater. You should be fine with just purchasing an inexpensive pump from the hardware store. I would definitely recommend just sticking with Vinegar, I know that some additives could void the warranty provided by the tankless water heater manufacturer.

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    Jack of all trades DonL's Avatar
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    Quote Originally Posted by guy48065 View Post
    Let me ask it this way...most people pay a pro to do this job. What pump do the pros use?

    Not sure you would want to spend the money for a pump like the pros use.

    You can get a 1200GPH pump like what is used for a pond that has a in and out.

    http://www.webbsonline.com/Item/Calp...FWpp7AodFTIA1w

    For safety the pump should be used on a ground fault interrupt.

    A smaller pump will work, just let it run longer, since you are not paying by the hour.


    Some places around here will charge $200 for this service.


    Good Luck.
    Last edited by DonL; 10-02-2013 at 08:49 AM.
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    DIY Member Killer95Stang's Avatar
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    I use a small 1/6 HP submersible pump from Harbor Freight. Add a 5 gallon bucket with about 3-1/2 gallons of Vinegar and two washing machine hoses (if you have tankless service taps) for circulation. I've performed the service on my Rheem condensing tankless twice since I self installed the unit over a year ago. Pretty easy, since the addition of the water softener kinda retards calcium build up.


    Adding the 25% off coupon from popular magazines makes this a winner!
    http://www.harborfreight.com/16-hors...ump-68422.html

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    DIY Senior Member guy48065's Avatar
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    Do you use that pump without a valve to throttle down the flow? 1350GPH through the small tubes in a tankless still seems like overkill to me?
    Romeo and Atlanta, MI

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    Jack of all trades DonL's Avatar
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    Quote Originally Posted by guy48065 View Post
    Do you use that pump without a valve to throttle down the flow? 1350GPH through the small tubes in a tankless still seems like overkill to me?


    That pump does not make that much pressure, and will not achieve 1350GPH in that application.
    Theory only works perfect in a vacuum.

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    Master Plumber master plumber mark's Avatar
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    the vinegar is the only solution to run through one of these tankless
    heaters, I have heard you should run it , or cycle it through with
    a 5 gallon bucket for a couple of hours...

    the cost to have it done is pretty high in Indianapolis
    I know of one plumbing shop that charges $300 bucks....

    I wont get involved with any of it....
    dont need any call back issues or get blamed
    that the unit is not working properly after the job is done....

  11. #11
    DIY Member Killer95Stang's Avatar
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    Quote Originally Posted by guy48065 View Post
    Do you use that pump without a valve to throttle down the flow? 1350GPH through the small tubes in a tankless still seems like overkill to me?

    Like said by DonL, no way that pump will flow 1350com in the above configuration. In all actuality, the flushing process is very uneventful. I just let it run for 45-60 minutes while i do some other chore in the backyard. When finished, I flush with system with clean water using the same pump and bucket. I then put the clean hoses and pump into the bucket with a lid and store them together till the next use.

    No need for some special high dollar pump when the one I posted can be had for under $50. If you still feel uneasy using it for the mild acid, then spend $15 on the extended warranty. They will just give you new one and throw the bad one in a pile.

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    DIY Senior Member guy48065's Avatar
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    Sounds like a plan.
    It's under $43 with the 20% coupon I found. I don't think I can do better than that.
    Thanks.
    Romeo and Atlanta, MI

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    Jack of all trades DonL's Avatar
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    Quote Originally Posted by guy48065 View Post
    Sounds like a plan.
    It's under $43 with the 20% coupon I found. I don't think I can do better than that.
    Thanks.

    Did you count the $10 for a good 5 gallon bucket ? . lol


    Have Fun.
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