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 Jason Haeger on
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It sounds like copper to me as well. I'll be watching this thread. I'm curious.
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Permalink Reply by Scott on
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Have you tested hardness? Maybe the softener doesn't work. What is that 400ppm? If it's all hardness that's like 24 grains. That would esplain the build up. We get that around here. I've seen boilers full of stuff like that.
Green flame, copper and salt.
Carbons are probably loaded up and are discharging. Hence the taste issue.
Muriatic acid, TSP, CLR and I've heard that Cascade dishwashing detergent works good in a pinch (though in our area it's now TSP free and doesn't work so well). We've taken to sand blasting the really bad ones.
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Permalink Reply by Keith Eckert on
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My guess is that the scale is likely what I have heard called "Silica" scale. It is not soluble in acid, but in an alkaline solution.
Copper is almost certainly what is turning everything blue-green. What is curious is that if my memory serves me well, cooper can more easily enter a solution with a PH below 7, generally typical of soft water (did you test pH?). My guess would be that the (over?) softened water is corroding the copper boiler and mixing with the scale.
We don't deal with much silica here, so not sure the best fix. I do know that steam and high pressure dissolve silica (upwards of 25 bars I think)...
It also could be Calcium Sulfate (what makes soy beans into Tofu), a chemical that looses solubility with higher temperatures which makes it notorious for heated waters systems. I think it is common in municipal water, just not where I am. Again, trying to remember, but it should be soluble in a strong acid (but you won't get any bubbling as it is not carbonate).
I think it is obvious, and I write this for anyone who else who is reading this. Even if Brady can work some magic to bring this machine back to life, if the water quality issues are not addressed the same problems will pop up again shortly. Here is a recent post on water quality needs.
I am curious to read what you figure out on this.
Keith
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Soft water does not corrode pipes (interweb myth). http://www.wqa.org/sitelogic.cfm?ID=366 High acidic water with a low ph/ low TDS will. And he doesn't have that with a TDS of 400ppm. He needs to find out what that is.
Brady - Go get a water test kit from Grainger or Homedepot and find out what that is. Or get a sample to me and I can test it.
Keith - You are in the Seattle area, right? While the water over there may be "soft". It is also quite acidic. It's all surface water.
Keith Eckert said:What is curious is that if my memory serves me well, cooper can more easily enter a solution with a PH below 7, generally typical of soft water (did you test pH?). My guess would be that the (over?) softened water is corroding the copper boiler and mixing with the scale.
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Thanks Scott. Just looked at how I worded my above post and should have worded it differently. I was not saying that the softened water in itself is corrosive, but was speculating on the role pH has on copper (or alloys containing copper). Lower pH is more corrosive for copper, and the softener likely dropped the pH. My guess was that the scale is silica, which is soluble in alkaline solutions, so the change of ph of the softener would cause the silica to precipitate.
I did a quick perusing of the article you posted, which was great, thanks. While the author only briefly summarizes a bigger study, the only specific metal they conclude is lead:
Results from the study shown no increased dissolution of lead in the softened water.
Do you know if they reported specifically to other metals somewhere?
As for Seattle water, it is hard to say. Seattle Public Utilities started to manipulate pH in the 1980's to keep it alkaline. On the upper east side, water here is almost always just slightly alkaline (7.4ish) in any tests I have done.
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It only takes a few ppm to reduce PH. He has 400ppm. That's comparative high.
The softener had nothing to due with reduced PH and eating copper. If there is an high purity RO after the softener, then that would have an effect on PH. But again, he has 400ppm. And we don't even know if there's copper pipe.
I haven't searched, but from the document -" WQA also has available other materials to show that ion exchange softening does not affect any of the factors which contribute to water corrosivity" And this is generally accepted.
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Permalink Reply by Brady on
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Thanks guys. Will upload a pic shortly.
Scott, that would be great! PM me your address and I'll mail you a sample.
TDS measurement was done with a pretty basic yet reliable meter. Test sample TDS varied considerably from day to day, possibly depending on how much water I flushed before measuring. High was 400ppm at the machine on first visit. On my next visit, I poked around under the counter and discovered a recently changed (March 2012) Cuno 8112S. Sampling upstream of that, after flushing a bit of water, gave me 300ppm. On both days, water sampled from other points at the store measured at my expected 51-53 ppm, 2.5 grains hardness - which is what Charlotte-Mecklenburg utilities provides at the tap.
Incidentally, I tried using my trusty Hach 5-B drop-count hardness test kit to measure hardness. When I added the reagent to the sample it turned orange instead of pink. Tried titrating and saw no change after 20 drops, so I quit.
I did test several samples with Hach 5-in-1 strips. The 400ppm (post filter) sample measured pH 6.5-6.8, Hardness 7 grains, Total Alkalinity 180ppm, Chlorine 0.
Will share more info as it develops.
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Also... copper pipes throughout the store. Water for coffee, tea, ice, and espresso theoretically passes through a couple of large softeners on the way into the store. I tested water at the drip brewer though and it was fine. These softeners are managed by a water treatment company - I thought the facilities guy said Everpure... but have not had any direct contact with them or the plumber. That might be a good idea, now that I type that.
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