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Treating Condensate from ModCon boilers? How important?

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hot_rod
hot_rod Member Posts: 22,147
on what the drain is connected to. In a new home with all PVC drain lines I doubt any harm would be done.

I'm on a septic tank and the warm condensate runs through the tank into a leach feld of limestrone. I'm not too concerned.

I'd expect the same with a system connected to a city wide sewer system, probably plenty of dilution waters. i don't recall seeing FA furnaces with condensate neautrilizers. They have been aronnd for 20 years.

Still, it is a simple and inexpensive device to build. I use a tube of 4" PVC with a closet flange on the bottom (plugged), for a base and a Fernco cap on top for ease of removal. Drill and tap a 3/4" PVC ell at top and bottom.

hot rod
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream

Comments

  • Richard Miller_3
    Richard Miller_3 Member Posts: 61
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    How important is it?

    Is there any inexpensive way to neutralize it? I saw a pic recently with a plastic tub (like one from Wal-Mart) with some white stuff in it that had the condensate running through it.
  • Steve Ebels_3
    Steve Ebels_3 Member Posts: 1,291
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    We use

    Chipped marble landscaping stone in a 5 gallon bucket. I have seen condensate take out old cast iron floor drains in a little over a year so yep, it's important.
  • Brad White
    Brad White Member Posts: 2,398
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    Here in Mass.

    I was told that the acidity can kill bacteria in a septic system and can certainly over time eat iron pipe, sewer or not. In fact, one school I recently did had a septic system and a water well deemed to be a water-works, so disposal of the stuff, neutralized or not, fell into the low-level industrial waste category.

    With two 2-million BTUH input condensing boilers, that could be 40 gallons of condensate an hour x $0.30 per gallon disposal cost... we went with cast iron conventional boilers.

    I used to use the 5-gallon bucket method but found that the plastic became more brittle than glass over time. Now I use a drum trap with marble chips. You can fabricate your own with PVC pipe, tees and end clean-outs to empty and re-charge with marble chips. I have had these run for two years with barely a rounding of the sharp edges. What goes in at pH of 4.5 comes out about 7.5 to 8.0 pretty consistently.

    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • I agree,

    with all the above reasons. I`m in "ABS country" so for my installs I make these-up.

    The factory-bought Triangle Tube ones are like this.

    Dave
  • Brad White
    Brad White Member Posts: 2,398
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    That's it, Dave!

    Thanks for the illustration.

    Is ABS the material of choice, or does "ABS" stand for "Above Big States"?
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • You`re always

    a "blast" Bradley LOL!
    BTW-I`m still figuring that church job(a next summer project), just been so busy I can`t keep at-it, but we`ll talk soon!

    Dave
  • Brad White
    Brad White Member Posts: 2,398
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    Uh, it's

    "Bradford", Dave.

    My mother called me "Bradley" once.

    Once.


    :)

    Cheers-

    Brad
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • Sorry Brad,

    Bradley, Braden whatever, I still enjoy you`re one-liners LOL!

    Dave
  • Leo G_101
    Leo G_101 Member Posts: 87
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    Wow, Dave

    a bit more fancy then mine, but same idea. 3" Abs cap, top and bottom, then 2 - 3 x 1 1/2 Tees, couple 1 1/2 elbows, done!

    I think I remember ME stating that they have had some underslab plastic drainage piping that was destroyed by untreated condensate. I believe that these were other companies installs, the ME's Co. had the "pleasure" of fixing.

    Leo G
  • Richard Miller_3
    Richard Miller_3 Member Posts: 61
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    OK, this doesn't make sense. A concern is being raised about possible damage to plastic pipe and yet everyone is using plastic pipe to build their treatment apparatuses.

    I am truly puzzled now!

    (Not dissing anyone. Just trying to sort it all out.)
  • Well Richard,

    I`m not a chemist , and don`t know what Leo G is referring to, but plastic seems to be the most economical and available materials to us, even the manufacturers use-it. Should they be SS, or glass? Not trying to be sarcastic, just curious.

    Dave
  • DaveStroman2
    DaveStroman2 Member Posts: 21
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    Here is a sample of one I made. I think it is important the drain the boiler into a stand pipe rather that a hard connection. It may prevent the condensate from backing up into the boiler if there is ever a blockage.

    Dave Stroman,
    Denver

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Nice Dave,

    I like that suggestion!
    Great minds sometimes think alike , first names too LOL!

    Dave
  • Plumdog_2
    Plumdog_2 Member Posts: 873
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    I think you mean cast iron was destroyed

    I have seen a condensate drip from a leaky vent pipe eat a piece of galvanized electrical coduit, and erode a little ravine out of the concrete wall where it ran down!
  • Tim_41
    Tim_41 Member Posts: 153
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    I've made mine own using a drum trap also. One thing that is important in the cold regions: you should drain it into a condesate pump. If you have a waste line that is not deep, the drip can freeze and than start blocking the the waste line with ice. Than you'll be thawing out a waste line. The pump will give a charge of water into the waste line and than stop until it pumps again.
  • archibald tuttle
    archibald tuttle Member Posts: 1,085
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    not all plastic created equal

    just happened to find this very thorough link on PVC acid tolerance.

    http://www.vylonpipe.com/techsheets/Chemical Resistance of PVC Pipe.htm

    Unfortunately this company does not also make CPVC or ABS so you can't get a side by side comparison.

    It lists chemical tolerances at 73 and 140 degrees F

    HCl passes both, but Sulfuric and Nitric Acids get conditional or failed marks at the higher temperatures.

    Still, PVC might last a long time, but would think twice about the actual acid composition of flu gases before dumping condensate into inaccessible plastic lines.

    Of course many of these boilers spec PVC for boiler flu piping these days which I think is more related to temperature than acid tolerance (some used to spec only CPVC or ABS) , but that is a guess since they are now specing PVC as acceptable in many cases.

    I'll gladly take anyone's link to a comparative acid tolerance chart and a chemical breakdown of acids in natural gas exhausts.

    Brian

    PS - Brad, Bradley, whats the difference when you're getting so old you can't hear what people call you anyway.
  • Leo G_101
    Leo G_101 Member Posts: 87
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    But the

    nuetralizer is in the plastic!

    Question, if you service your mod/cons once a year, and the marble chips still look great, do you still change them out every couple of years, or wash them? this does not seem to be neccesary to me, but others have said that they do change the chips once every couple of years.

    As it now seems that 7 out of every 10 boilers I install (and talking to others, it seems about the same ratio) is a mod/con, it just seems prudent to nuetralize before going into the public sewers. After all, it is still my tax dollars that will be raised to repair these buried lines!

    Leo G
  • ALH_4
    ALH_4 Member Posts: 1,790
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    Neutralization in pipes

    Or perhaps it is neutralized once it makes contact with underground concrete sewer pipe, if present. I agree that as the number of households with condensing appliances increases, this will become a bigger issue.

    The pellets in the Viessmann kit do dissolve over the course of a few years. I haven't used marble chips.
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
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    My hideously oversized neutralizer using a Rubbermaid storage container and crushed limestone is still fine after 3 heating seasons. The plastic is highly pliable.

    I originally put a 5-gallon bucket of crushed limestone in the device and while I didn't mark the level, I would swear that at least 1/4 of it is gone.
  • Brad White
    Brad White Member Posts: 2,398
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    When the Chips are Down

    I have run chips for over two years without changing them but I do test the pH now and again. That is where it counts and so far pretty "neutral" so to speak.

    I buy small marble chips in the garden department of a large home improvement super-store where people run around with orange aprons. One bag will last for a generation at the rate I am going.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
    von08
  • archibald tuttle
    archibald tuttle Member Posts: 1,085
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    abs, cpvc chemical resistance charts

    http://www.k-mac-plastics.net/data sheets/abs_chemical_resistance.htm

    this chart says ABS is sensitive to Sulphuric and Nitric Acid at both room temperature and 140 degrees. So it doesn't really rate any better than PVC.

    http://www.pep-plastic.com/manufacturers/spears/pdf/cpvcchart.pdf

    this cpvc chart does not recommend use with nitric acid at high temps (although the chart contemplates 180 deg. instead of 140 deg. F) and cautions against higher concentrations of sulfuric acid.

    It seems that emperical experience suggests that some folks have had trouble with some plastics as drains for condensing boilers. Still wondering what this means for the plastics in the flu. Most of this looks like longer term. I mean stainless flus rot eventually. like say those stainless grill burners that I'm replace every year or so.

    Brian
  • [Deleted User]
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    NO problem with plastic drains...

    it was cast iron drains that were rotted out due to condensate...

    I am not personaly aware of ANY issues with condensate and plastic, other than someone here mentioning that their 5 gallon bucket seemed to degrade quicker than usual (Brad White??).

    My 5 gallon bucket has been seeing condensate for 5 years and is not showing any signs of degradation.

    We too use crushed white marble, and it raises the pH a 4.5 to around 7 before discharging to the sewer.

    ME
  • archibald tuttle
    archibald tuttle Member Posts: 1,085
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    no problem with plastic drains

    sorry, I can't quite figure where is the best place to place responses., i.e. mid thread after new comment, but you usually look for new comments at the bottom, so I'll just stick it here.

    Mark, thanks for your note that it was CI drains that were rotted by condensate in the example above.

    the science geek in my wants to know what kind of acid is in the condensate. I'm guess nitric is possibility -- don't know about the sulfur content of gas as to sulfuric but thought it was marginal compared to oil.

    It is just interesting to note that manufacturers don't rate these plastics as tolerant of those acids at condensing boiler flu temps. I imagine that we're probably talking dilute concentrations and a long time to see the effect if at all such that there aren't observed instances of plastic susceptibility to acid even without neutralization.

    Brian
  • [Deleted User]
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    I am NOT a chemical engine ear....

    nor do I play one on TV, but my gut tells me that the make up of the acid is probably carbon based on natural gas boilers because we test the flue gasses for carbon dioxide and carbon monoxide. Based on the web site information you have provided, these materials are totally compatible with PVC.

    But, as I previously stated, I am not an expert in that field.

    Neutralization is a code requirement under the IMC, and the IPC. As for gas forced error furnaces not eating out any cast iron drains, I suspect they don't condense much :)

    We tested a 500K Knight that we fired today, and post neutralization pH was around 7 on a litmus scale, and it was going in around 4, same scale. Crushed white marble media.

    IF, this condensate has any negative effects on PVC or ABS, we'll probably be LONG gone before it raises its ugly head, unlike cast iron drain issues, which show in 5 years or less...

    ME
  • Bill Clinton_5
    Bill Clinton_5 Member Posts: 38
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    The acid in condensate is in fact carbonic acid which is the probuct of dissolving CO2 in water. Same stuff that puts the bubbles in my Diet Pepsi, or in Mark's champagne.

    Once had to replace 20+ year old cast iron piping under a slab in a bar. The whole bottom was eaten out from the carbonic acid of carbonated drinks dumped in the sinks. Boiler condensate is a lot weaker acid than Pepsi, but it will mess with cast iron. I think plastic is fine with it: That's what the Pepsi bottle is made of after all.

    Bill
This discussion has been closed.