A strange buildup issue
Here's one I haven't seen before, and am looking for some help dealing with.
A client has been running a machine for a while on a waterline that has some sort of previously-unknown contamination issue. I have no idea what the contaminant is, but the water measured 400ppm TDS vs 53ppm typical for our area. The water is softened and also filtered through a chlorine/sediment cartridge. It tastes terrible - metallic and mineral.
The original complaint was for problems that I traced to the boiler, heater, and heat exchangers having a significant buildup of a blue-green crust. I have the machine on my bench now, and tried a couple of soaks with Dezcale today and it didn't touch it. Will try something more assertive tomorrow, but I'm not optimistic.
Like I said, the crust is blue-green. What little did dissolve into the descale solution turned the solution a strong Windex blue. Just for fun, I held a small chunk over a lighter and it turned the flame green. If my old memories from chemistry serve me, I think this suggests some sort of copper?
Any thoughts about what I may be looking at here? Or what I might use to remove it without damaging the copper boiler and pipes?
Thanks!
Replies to This Discussion
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Permalink Reply by Brady on
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That's the view inside the heat exchanger, boiler, and at the level probe. Those pics are rotated 90 degrees ccw, didn't catch it before I uploaded.
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Permalink Reply by Scott on
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From the Hach website (does any of this sound like what you saw?) -
"My sample turns a purplish color with my hardness test but never turns blue no matter how much EDTA I add. What is wrong?
This is an indication that your sample contains an interfering metal. Dilute your sample and repeat the test. This may dilute the interfering metal to a level at which it does not interfere.
If this helps, multiply your result by the dilution factor. If this does not help, follow the suggestions in the interference section of your procedure or in the Water Analysis Handbook.After my sample turns blue, it keeps fading back to pink. What should I do?
If the sample contains high levels of calcium (>200 mg/L as CaCO3), calcium carbonate will precipitate due to carbonate in the UniVer3 reagent. The sample will turn blue but then slowly fade back to pink as the calcium carbonate slowly redissolves.
Keep adding drops of the Hardness 3 solution until the sample remains blue. You can also start over and add several drops of the Hardness 3 titrant before adding the UniVer3. Include the initial drops when counting the total number of drops.My sample turns a light pink-brown color after adding the UniVer3 from my hardness test kit, why is this?
If there is hardness in your sample, the color after adding UniVer3 should be pink or red. Iron and manganese can interfere with the UniVer3 and cause the pink-brown color, and also interfere with the endpoint color.
Repeat the test with a fresh sample, but add 1-2 drops of the Hardness 3 titrant first, then add the UniVer3, and then continue adding the drops of the Hardness 3 solution. The titrant will complex the iron and manganese so that they will not interfere with the reagent. Include the initial drops when determining the hardness concentration."
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A friend just emailed me this:
"I have heard that when electricians use the water lines in a building to ground it can sometimes cause electrolysis of the copper in the lines."
That's another interesting possibility to consider, especially given the water's low pH. Thoughts?
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Also, an update.
I was able to remove most of the scale this morning using a fairly concentrated (10% HCl) Muriatic acid solution. (Incidentally, I'm also now the proud owner of a lovely 3M acid-fume respirator). This leaves only the inside of the heat exchangers left to descale, which should not take long once I figure out how to get the acid safely in and out.
Thanks to all for your help so far. Will post back with more progress as it happens.
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Permalink Reply by Keith Eckert on
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Curious if you saw bubbling when you used the Muriatic Acid? Also, I thought about the copper corrosion being a result of a bigger electrical issue, and emailed an electrician friend of mine yesterday to see what he thought. Haven't heard back yet but will let you all know his response when I do.
Keith
Brady said:Also, an update.
I was able to remove most of the scale this morning using a fairly concentrated (10% HCl) Muriatic acid solution. (Incidentally, I'm also now the proud owner of a lovely 3M acid-fume respirator). This leaves only the inside of the heat exchangers left to descale, which should not take long once I figure out how to get the acid safely in and out.
Thanks to all for your help so far. Will post back with more progress as it happens.
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I didn't see significant bubbling (nothing like the reaction you'd get from traditional Calcium scale with descaler), the stuff just calmly melted.
FWIW, I think the water comes in to the store from a mall, through the back wall. The water line leading to the espresso machine comes up out of the concrete. So if there was a device grounded to this pipe that happened to be leaking voltage, it would find a convenient exit in this particular line. That would certainly explain why the problem seems to be isolated to this line. That might also explain why the problems didn't start until several years after they opened.
Keith Eckert said:Curious if you saw bubbling when you used the Muriatic Acid? Also, I thought about the copper corrosion being a result of a bigger electrical issue, and emailed an electrician friend of mine yesterday to see what he thought. Haven't heard back yet but will let you all know his response when I do.
Keith
Brady said:Also, an update.
I was able to remove most of the scale this morning using a fairly concentrated (10% HCl) Muriatic acid solution. (Incidentally, I'm also now the proud owner of a lovely 3M acid-fume respirator). This leaves only the inside of the heat exchangers left to descale, which should not take long once I figure out how to get the acid safely in and out.
Thanks to all for your help so far. Will post back with more progress as it happens.
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Permalink Reply by Mickael on
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That is very much copper and lime. On something this bad the only luck I've had is soaking the boiler with Muriatic Acid. Not fun stuff but it works just need to be really careful with it.
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I have had to have no less then 6 concrete floors cut to remove/replace rotted copper pipe, in the last decade while working for Big Green. If the wrong pipe is used ( I believe it is type "L") it will rot rather quickly. I have no answer as to why, might have something to do with the concrete itself? Maybe some or all of the TDS/sediment is from eroded concrete and copper? Would explain why you only find it on that line and not the rest of the building. Salt would attack concrete through the leak in the pipe. Put pressure gauges on each end of the line and a water meter, see if it's leaking.
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Yeah, that makes sense. If the water started at a hardness of 2 and ended up at 7, it would have had to pick up some (119ppm - 34ppm = 85ppm) calcium or magnesium somewhere. The copper couldn't account for the entire 350ppm increase or else the hardness wouldn't have increased.
Scott said:I have had to have no less then 6 concrete floors cut to remove/replace rotted copper pipe, in the last decade while working for Big Green. If the wrong pipe is used ( I believe it is type "L") it will rot rather quickly. I have no answer as to why, might have something to do with the concrete itself? Maybe some or all of the TDS/sediment is from eroded concrete and copper? Would explain why you only find it on that line and not the rest of the building. Salt would attack concrete through the leak in the pipe. Put pressure gauges on each end of the line and a water meter, see if it's leaking.
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Spoke with the owner of my company about this, he thinks the copper is from electrolysis and the water is coming from a source other than the city, probably a well on site. He says he's found malls will sometimes have a well on site, even though there is city water. Or there is separate irrigation water that was tapped into. And that softener is definitely not working.
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Permalink Reply by Edwin Poon on
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The pipes in the concrete should have been wrapped in plastic before concrete was poured over them because the concrete will rot he pipes out, and when I worked for the water company we learned about electrolyses from dissimilar pipes, even brass on copper causes electrolysis just at a slower rate. Maybe check the water lines to see if there is dissimilar pipe connection.
Scott said:I have had to have no less then 6 concrete floors cut to remove/replace rotted copper pipe, in the last decade while working for Big Green. If the wrong pipe is used ( I believe it is type "L") it will rot rather quickly. I have no answer as to why, might have something to do with the concrete itself? Maybe some or all of the TDS/sediment is from eroded concrete and copper? Would explain why you only find it on that line and not the rest of the building. Salt would attack concrete through the leak in the pipe. Put pressure gauges on each end of the line and a water meter, see if it's leaking.
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