I need help cleaning the hot water coil in my oil fired furnace.

Discussion in 'HVAC Heating & Cooling' started by Mad Plumber, Jun 3, 2010.

  1. Mad Plumber

    Mad Plumber Mad Skills

    Joined:
    Aug 13, 2005
    Occupation:
    Plumming
    Please send me a link on DYI to clean this coil. Is there a kit? Where can I get it? Is it a difficult process? Our hot water pressure has rapidly decreased over the past 6 months and we were told it is the residue build up on the coil to the fault of our water company however we cannot find anyone to clean it....our furnace is only 5 years old!!! I am not prepared to settle for the lack of pressure.

    Thanks so much,

    Doreen
     
  2. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    If it has scaled up in under 5 years that's usually an indication of water-hardness. An acid flush may solve it temporarily, but it's likely to scale up even more quickly the second time around. A better investment (but more money, for sure) would be to spend the money on an indirect-fired tank HW heater and a water softening system. An indirect will run higher efficiency too, since you can let the boiler cold-start, and the tank has far better insulation & capacity, and you can run it at lower temp than the boiler for lower standby loss. (Oil is expensive, and embedded coils are about the least-efficient legal way to heat hot water when it's not an active heating season.)

    An acid flush requires a small acid-proof pump & tubing, breaking the system open, recirculating the acid solution through the coil for some period of time (which will vary with scale thickness & type) then rinsing it for a half hour or so running fresh water through it with the pump. Sometimes white-vinegar is adequate, but otherwise buy a gallon of purpose-designed descalers, which are sligthtly more acidic. Don't try mixing your own out of muriatic acid, or suphuric acic etc (unless you have a degree in chemistry and can live with the results of an error.)
     
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  4. don blonde

    don blonde New Member

    Joined:
    Aug 1, 2016
    Location:
    New York
    I just had a plugged coil plumber wanted 100 bucks to acid flush it. With no guarantee. I read a few posts on here just joined the forum. I got one of those cheap 10 dollar drill pumps at home depot. 1 gallon of acidic toilet bowl cleaner, 10 percent acid. The whole deal cost me 20 bucks.
    shut the water off coming into the coil. shut all the valves going out to the house. Opened the two valves on the bottom of the coil. flushed for about 5 minutes. Works like a charm how nice to have hot water and good water pressure again.
     
  5. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    Hopefully you won't have pickled the coil to the point that pinhole leaks develop causing the higher pressure of the potable side from overpressurizing the heating system.

    If the coil fails it's usually not worth replacing it these days. Depending on the oversizing factor for the space heating load and age of the boiler and your fuel costs, which of the alternate water heating options are most appropriate will vary.
     
  6. Tom Sawyer

    Tom Sawyer In the Trades

    Joined:
    Nov 29, 2010
    Location:
    Maine
    It's not a diy job. Valves need to be cut in to stop any possibility of the acid getting into the potable system and the pump is a special ceramic unit signed to pump acid. Even done professionally, there is more than a 50/50 chance that removing the lime will Expose pinholes in the coil itself. My advice would be to seek an alternitave method of making hot water. Either by indirect, electric or gas fired. As an aside, what you have there now is quite possibly the most inefficient and wasteful way to make hot water.
     
    Dana likes this.
  7. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    I dunno, you can probably heat water somewhat less efficiently in a kettle over an open coal grate, no? :)

    An indirect can make sense if the boiler is reasonably new, and not ridiculously oversized for the space heating load. Monitor the heating system pressure- if it's rising over days/weeks you almost certainly have leaks in the coil. At that point we can figure out what makes the most sense going forward.
     
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