Yellow water when emptying La Pavoni Europiccola boiler - Page 2

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bobsy (original poster)
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#11: Post by bobsy (original poster) »

homeburrero wrote:This is a conundrum. Just to be sure, whenever using a TDS meter to make a comparison make sure you measure both at the same temperature, ideally 25 ℃ (77 ℉).

The 20 ppm reading indicates nothing is wrong with your RO. The fact that you can use rpavlis and still get the problem implies that it's not related to the lower alkalinity and pH of the RO.

If you are putting 20 ppm into the boiler, heating it, and getting 150 ppm out implies that a lot of something inside the boiler is dissolving out into the water. The fact that it is dissolving out implies that given enough flushes it should eventually disappear. I would try making up a couple gallons of that RO, spiking it with a tiny pinch of bicarbonate, mixing well, and then recording the TDS reading at room temp. Then use that water to repeatedly rinse the boiler, heating it and letting it cool. Periodically measure the TDS at room temp of the rinse water and hopefully it will eventually drop to the same TDS as the feed water (and become clearer.)

One thing that we've seen that will keep clouding a boiler's water is a ruptured element that leaks the magnesium oxide insulating filler into the water. This normally gives you a white cloudy precipitate in the water and I don't think is the case here.
I sincerely appreciate the suggestions so far!
I'm a bit confused with how little bicarbonate you're suggesting to add. When I was trying to get rid of non food safe oils I had used to restore my EP (cycles of dish soap, ever clear alcohol, puly caf etc), I also did cycles where I would use one tea spoon of baking soda mixed with about 650ml of RO water, boil it in the boiler, and pour everything out (to neutralize smell and taste). Is using that amount of baking soda bad for the boiler?

Finally, with regards to the water being absolutely clear after boiling when using tap water (with TDS over 400), what new information does that give us?
Thanks again!

bobsy (original poster)
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#12: Post by bobsy (original poster) »

By the way I also tested with Alkaline water this morning (PH 9.5) and to my surprise the water was yellow too. I thought higher PH would solve the problem.

bobsy (original poster)
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#13: Post by bobsy (original poster) »

Ok, final update. I tested my RO water for the pH level: 6. I added baking soda to my RO Water to bring the pH to 7, and I no longer see the discoloration.

What's interesting is that it's not just an acidic issue, it seems the problem is also there with high pH alkaline water (9.5). Looks like the boiler is pretty sensitive and needs pH around 7 to behave normally.

Thank you all for the help along the way.

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homeburrero
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#14: Post by homeburrero »

bobsy wrote:I'm a bit confused with how little bicarbonate you're suggesting to add.
When starting with fairly pure RO water it takes very little bicarbonate to bring the pH up into the 7+ range. I was thinking that a low mineral water to rinse might in theory be more conducive to safely dissolving whatever is causing that yellow color.

bobsy wrote:I also did cycles where I would use one tea spoon of baking soda mixed with about 650ml of RO water, boil it in the boiler, and pour everything out (to neutralize smell and taste). Is using that amount of baking soda bad for the boiler?
You can use a lot more than that with no worry about boiler damage. Sodium bicarbonate is amphoteric - it will buffer acids at low to neutral pH and will buffer bases at high pH. It also dissolves readily, is easily rinsed, and safe to drink.

bobsy wrote:What's interesting is that it's not just an acidic issue, it seems the problem is also there with high pH alkaline water (9.5). Looks like the boiler is pretty sensitive and needs pH around 7 to behave normally.
Interesting, and beyond my chemistry chops to guess what might be going on here. Wish Dr. Pavlis were still with us.
Pat
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bobsy (original poster)
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#15: Post by bobsy (original poster) »

reviving this thread.

Unfortunately I have not solved the problem entirely. Even if I use tap water - which seems to be in the pH 7 range according to the testing kit I have (bottle with drops and color range). I still some some taint in the water coming from the group head.

How can I troubleshoot the issue to find out if the problem is my water or if somehow my boiler is damaged?
Is there a mixture solution cycle I can go through to "reset" the boiler and "start fresh"?

RobAnybody
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#16: Post by RobAnybody »

bobsy wrote:I still some some taint in the water coming from the group head.
So only when the water coming through the group head or also with water that was in the boiler for a while like before?
Have you checked the circlip in the top of the group head? In some Pavoni's this is made of mild steel instead of stainless which could cause the discoloration in the water. Another option is the type of grease or rubber you use, especially since you mentioned before that the yellow colour appeared both at low and high pH (both basic and acidic water will dissolve grease and some fresh bromobutyl rubbers will leach a yellowish plasticiser (though Viton is more common in espresso machines).
I wouldn't worry about the boiler if you use a bit of bicarbonate in the water. None of the metals used on the inside of the boiler (nickel,.copper) turns yellow when dissolved.
LMWDP #647

bobsy (original poster)
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#17: Post by bobsy (original poster) »

Not just from the group head, but also the water sitting in the boiler. If I dump that water out straight from the boiler, it's not crystal clear like the water I pour in. There is some slight taint (not nearly as bad as my original post when I was using RO water).

Are you sure about your statement regarding the metal in the boiler? I heard from different sources acidic water will cause copper leaching and would explain that yellow/reddish taint.

I'm wondering if the problem is still the water, that it might be somehow still a bit acidic and causing a little leaching still. But would 0.2 or 0.3 pH range make that much of a difference? I can't accurately measure the pH with that drops kit, but it seems to be in the pH 7 range (which I would expect from city/tap water).

Or maybe that bit of discoloration *is* normal, and I should simply dump the water from the boiler every X days - someone correct me if I'm wrong.

To answer your question about the group head, I have rebuild that machine from the ground up back in October, and all washers and gaskets and other parts I got from espressocare.

I've stopped adding baking soda to my water as I figured my tap water being in the pH 7 range, that mixture wouldn't bring any benefit (and I have not noticed it prevents discoloration anyway).

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homeburrero
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#18: Post by homeburrero »

Good call on the circlip by RobAnybody -- is a frequent cause of iron oxide (rust) corrosion, and that might give you a yellowish tinge. Be sure that your rebuild parts included a new stainless steel circlip (It probably did, if from Stefano's espressocare.)

And I agree that yellowish water would not indicate copper. Dissolved copper corrosion would be blueish.

Note: Suspended Cu metal or Cu₂O nanocrystals *might* give you water with a reddish or yellowish tinge, but I can't imagine that's what you have here. The copper oxide layer in these machines is primarily a dark brown copper(II) oxide, and if it's removed by acidic or caustic water, it dissolves to blue copper salts - acetates, citrates, chlorides, carbonates, hydroxides of copper are all blue or green.
Pat
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bobsy (original poster)
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#19: Post by bobsy (original poster) »

Thanks homeburrero - glad you clarified my wrong assumption with copper leaching and the yellowish/reddish color.

What does that leave me with? Something in the boiler that's causing the rust? As far as I know, parts in the contact with the inside of the boiler are all factory. The exception is the heating element (brass) itself, which I got from Gabor a few months ago.

Is there a mixture I can use to get rid of any rust that I can safely use without damaging the machine (something I can use without having to dissemble it)?