Click here to Find a Contractor in your area.
In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Need to contact us? Visit

coil flushing

jaybeejaybee Member Posts: 128


  • KenKen Member Posts: 1,640
    Two things I learned the hard way..

    It has always been our experience that tankless coils lose thermal performance from calcium carbonate (hardness) build up within the coil. When the boiler water is in the 150°F and over range, Calcium Carbonate precipitates out of solution and scales on the copper insides - choking off flow and reducing thermal transfer.

    What puzzled us recently in one instance was that flow was hardly restricted - but thermal transfer was dropping off.

    Acid (muriatic/hydrochloric) is the natural "solvent" for the CaCO3 build up. In a unusual situation recently, we had lousy output from a large boiler tankless coil used for a process tank. We vowed to fix the problem with an acid pump out. After agressively acid cleaning the coil for an hour or so, we found no improvement in coil performance, so acid claned it again!

    Still no improvement. Baffled and frustrated, we pulled the pump apart (assuming the thermal transfer might be affected by a compromised impellor) only to find it fine. So we acid cleaned it yet again.

    After brainstorming for a week, we went back and decided the one condition we had never experienced before was the only possible problem. That being the boiler water side of the coil must be the area of "blockage." With great difficulty we unpiped all the boiler connections and obstructing piping and pulled the coil. The coil was plugged solid with some gook never before witnessed. This was a steam process boiler that we maintain regularly and clean the water side as well thoroughly, and to this day have no idea where the gook that plugged the coil's outer surface and in fact the entire bundle was, or how it got into the system!

    Once hosed off and scrubbed with stiff bristles, it was re-installed into the boiler block and all problems disappeared. A very costly job. We ate all the time and materials used on trying to clean a coil that already was clean (on the inside) - as well as the labor and materials to re-pipe half the boiler just to get that sucker out of the block!

    That was one of the things we learned the hard way. The other is to think outside of the box. We should have known the lack of a restriction would imply the probablem was NOT a CaCO3 build up within the coil. How could it have been?

    Back to your question.

    Being that acids are involved and no one really makes a good acid cleaner that differentiates between copper and CaCO3 - other than that the latter disolves very quickly in the presence of low pH (acid) and thankfully copper disolves extremely slowly in acid - 15-20 minutes being the time-frame being pondered in this illustration - and most if not all CaCO3 will be dissolved in 15 minutes while a trace of copper may be lost in the same time frame, you still need to be extremely careful around these products. Acid is acid period. Chemical burns are common and we only get one pair of eyes in this life.

    If you are not experienced in this stuff, I urge you to have a professional coil cleaning service bang this one out. The consequences of not knowing if it even needs doing, susggests extreme caution on your part.

    This one may be better left for a "specialist." Unless of course you are already blind and own a full body cover, rubber diving suit?

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • EdEd Member Posts: 164
    Coil Flushing


    Are you a contractor planning to attempt the job, or the boiler owner?

    PS,,, Please don't yell into these old ears.


    Ed Carey
  • Ken D.Ken D. Member Posts: 820

    After over 25 years, one thing I have learned is unless the boiler is brand new, I would just replace the coil. By the time you spend all of that labor, you would be better off. If the coil is very old, the acid may cause it to go into holes as it not only removes the scale, it also removes some of the copper. The previous post give you an idea of the problems you can run into. The old coil will scale up quicker than a new one will. Hope this helps.
  • GaryDidierGaryDidier Member Posts: 229
    coil flushing

    The results from coil flushing can be marginal. Also it is a messy and dangerous procedure. Like Ken experienced, many times an internal flushing produces no change because the external side of the coil is sludged up. I no longer will do "coil cleaning" but instead offer to flush the boiler side water and install a new coil. This costs more upfront but produces excellent results. You could also quote out an an indirect water heater install. Hope this helps,

    Gary from Granville
  • WeezboWeezbo Member Posts: 6,232
    It isnt worth the time materials and aggravation.

    Done enough gave the tools AWAY ;) how does this one sound?coils clean take the coil out put it back in find the 1 &1/2 is clogged out side of the coil in the risers to a 100 gallon water heater.... two coils....twice as much fun.
    how about break a bolt Find a gasket? what about clean the coil discover why? and my all time favorite remove the coil not even be able to get a blasted Plate. no, really, i dont Have to. i will leave it in the hands of those far more Qualified than myself ;) :)) if you the home owner plumber find the time and money to do all that you would have been ahead of the game to install an indirect hotwater maker. If you are going into the business then May i suggest you invest in easy outs, reverse drill bits, taps, stainless steel bolts stainless steel flat washers,brass nuts catapillar anti seize,gasket material and some form somewhere that says time and material to r and r a coil.when Cleaning it.Oh and a slide hammer phillips for the particularily objecting screws that wont come out of the tri aqua stat clamp onto the well. Have fun:)
  • !/2 the battle

    of pulling a coil could be made much simpler if some sort of no seize is installed in the coil bolt holes before installation . Fat chance of getting every boiler installer to do it though . Personally , I wrap Teflon on the bolts and a little moly grease in the holes - the coil bolts on my own boiler came out effortlessly this way .

    Weil Mclain is way ahead of the game with their O ring for the coil instead of a traditional gasket . And their studs and brass nuts give you double the chance to pull em out .
  • LeoLeo Member Posts: 767
    WM O Ring

    Hey Ron,

    The O Ring is good but if you replace the coil with an EverHot coil it comes with the traditional gasket. The inlet and outlet are also reversed.

  • I wouldn't use

    the regular gasket that comes with the Everhot . Weil made the coil hole surface with that " captured seal design " O ring in mind . A regular gasket in there , where the surfaces will not be truly flush , might not be the best idea .

    A regular gasket has a few flaws - the area around where the hole is for the bolt is very small , and the gasket itself will dry out eventually , and leak . I'm thinking the Weil design and material for the O ring will last longer . I hope it does .
  • WeezboWeezbo Member Posts: 6,232
    Oh ! Diddle i mention 3M glue and o ring material? :))

  • We see the accumulation

    on the boiler water side of the coil all the time , when we pull em out for mungo . We see it mostly with steam , but many hot water boilers will have a limited amount of spooge . On water boilers it's most prevalent on older clunkers that have had the same water in them for decades . I bet a good water treatment would keep the outside of the coils clean much longer . Funny fact is the internal part of the coils look pretty good when we pull em .
  • EdEd Member Posts: 164
    Removing tankless coils

    A tool I would NEVER be without when removing a coil is a Nut Cracker. (No that is not a customer that gives you grief :)

    It is a tool that cleanly cuts the coil bolts off of the studs, without any rotating force like is exerted by a wrench or socket. That rotating force on a very rusty stud is what usually breaks some of them off.

    Just have a new set of bolts & washers and a wire brush with you when you install the new one, and you're all set. If the stud does break off, then it was probably so rusted already that you could not have saved it.

    The link attached is the type I use. I found the link in a search. It is really long so you will have to cut & paste it (about 5 seconds), or spend about an hour entering it. The tool shown has an offset which makes it really easy to work with.

    I have had the one I use for about 30 years.


    Ed Carey
This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!