# Pavoni and copper leaching



## TomHughes (Dec 16, 2019)

Does anyone else use their Pavoni with RO water or distilled water? 
I suspected something funny when I could smell an odd smell coming from my pavoni boiler. 
I also tasted the water from it and it tasted metallic.

I have been using RO water with a small amount of mineralisation back in by the machine, to take it to 20tds.

I have just tested the water from it with a strip, I am not sure it was reading right but it didn't even register on pH, which starts at 6.2. So It would seem it's pretty acidic.

I've never bothered adding any bicarb back in, but I guess this would be the solution?

I'm slightly worried I'll have damaged the boiler, or that I will have been consuming huge amounts of copper for a while!


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## Nopapercup (Nov 6, 2016)

I've been using water from the Osmio for the last 18 months with my Pavoni. I don't add anything to it and I haven't noticed anything wrong with the water


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## TomHughes (Dec 16, 2019)

Nopapercup said:


> I've been using water from the Osmio for the last 18 months with my Pavoni. I don't add anything to it and I haven't noticed anything wrong with the water


 Have you measured the pH of it? 
I tried tasting the water from inside the boiler and it was definitely metallic in taste. Not sure where the funny smell is coming from either!


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## DavecUK (Aug 6, 2013)

TomHughes said:


> Have you measured the pH of it?
> I tried tasting the water from inside the boiler and it was definitely metallic in taste. Not sure where the funny smell is coming from either!


 I measured the pH with a pH meter Tom, sounds like you are not doing it right....


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## facboy (Dec 13, 2019)

that TDS meter is wrong, it says there are 35 parts in there but i only see 2 😹.


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## TomHughes (Dec 16, 2019)

DavecUK said:


> I measured the pH with a pH meter Tom, sounds like you are not doing it right....
> 
> 
> View attachment 52325


 Thanks Dave, that makes me feel better, although yours is adding back 35tds? Mine comes out around 15-20, started off at 40. Does my Mg/Ca cartridge need a change?


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## DavecUK (Aug 6, 2013)

TomHughes said:


> Thanks Dave, that makes me feel better, although yours is adding back 35tds? Mine comes out around 15-20, started off at 40. Does my Mg/Ca cartridge need a change?


 Not necessarily Tom. The membrane (any RO membrane) has a rejection % e.g. 98% etc.. as the Osmotic concentration in the supply Pitcher increases (the water is recycled back into it remember, no drain) the Osmotic potential increases. If it started at 200 in the supply pitcher, on the 5 litre mark, it will be approx 250 at the 4 litre mark and 333 at the 3 litre mark, followed by 500 at the 2 litre mark etc.. (man math simplified). Ergo the TDS of the water coming out at 2 litres will be 2.5 times that when you first refill the tank.

Depending on how you use the water from internal storage tank of RO purified water will dictate a varying TDS over time. The Mg/Ca cartridge can only do so much, and again it's effectiveness depends on usage. e.g. draw water, cartridge damp, time elapses, draw water and initially it pumps through catridge with a higher Ca/Mg conc. If you draw a large amount, the cartridge can only remineralise so fast. If the water was very acidic it would remineralise faster of course...but it's not.

If your Pavoni boiler is copper (not brass), and you are concerned *add 0.1g sodium bicarb per litre (as a GP you will know this has no health risks at all)*. It will buffer any minute amount of acidity and form a thin layer over the inside of the boiler that will remain microscopically thin. It may help with the taste, although I can usually taste the metallic nature of copper boilers. Oddly enough the only one I can't taste is the boiler in the Crem One 2B LFPP and i have no idea why?.

P.S. Don't try and weigh the bicarb unless you are making it as a fraction in water...

An article I wrote well over a decade ago....

http://coffeetimex.wikidot.com/ro-water-copper-corrosion


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## TomHughes (Dec 16, 2019)

DavecUK said:


> Not necessarily Tom. The membrane (any RO membrane) has a rejection % e.g. 98% etc.. as the Osmotic concentration in the supply Pitcher increases (the water is recycled back into it remember, no drain) the Osmotic potential increases. If it started at 200 in the supply pitcher, on the 5 litre mark, it will be approx 250 at the 4 litre mark and 333 at the 3 litre mark, followed by 500 at the 2 litre mark etc.. (man math simplified). Ergo the TDS of the water coming out at 2 litres will be 2.5 times that when you first refill the tank.
> 
> Depending on how you use the water from internal storage tank of RO purified water will dictate a varying TDS over time. The Mg/Ca cartridge can only do so much, and again it's effectiveness depends on usage. e.g. draw water, cartridge damp, time elapses, draw water and initially it pumps through catridge with a higher Ca/Mg conc. If you draw a large amount, the cartridge can only remineralise so fast. If the water was very acidic it would remineralise faster of course...but it's not.
> 
> ...


 Great thanks, how would I know if the boiler is copper or brass? 
It certainly looks more like copper. 
It's a 1995 euro.


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## DavecUK (Aug 6, 2013)

Dunno, probably copper I think the later ones were brass...


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## Nopapercup (Nov 6, 2016)

TomHughes said:


> Have you measured the pH of it?
> I tried tasting the water from inside the boiler and it was definitely metallic in taste. Not sure where the funny smell is coming from either!


 No, it's not something I thought about until this post.


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## Nopapercup (Nov 6, 2016)

DavecUK said:


> Not necessarily Tom. The membrane (any RO membrane) has a rejection % e.g. 98% etc.. as the Osmotic concentration in the supply Pitcher increases (the water is recycled back into it remember, no drain) the Osmotic potential increases. If it started at 200 in the supply pitcher, on the 5 litre mark, it will be approx 250 at the 4 litre mark and 333 at the 3 litre mark, followed by 500 at the 2 litre mark etc.. (man math simplified). Ergo the TDS of the water coming out at 2 litres will be 2.5 times that when you first refill the tank.
> 
> Depending on how you use the water from internal storage tank of RO purified water will dictate a varying TDS over time. The Mg/Ca cartridge can only do so much, and again it's effectiveness depends on usage. e.g. draw water, cartridge damp, time elapses, draw water and initially it pumps through catridge with a higher Ca/Mg conc. If you draw a large amount, the cartridge can only remineralise so fast. If the water was very acidic it would remineralise faster of course...but it's not.
> 
> ...


 Would you recommend adding bicarb then @DavecUK and if so is it just as simple as adding 0.1g to a litre of water?


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## DavecUK (Aug 6, 2013)

Nopapercup said:


> Would you recommend adding bicarb then @DavecUK and if so is it just as simple as adding 0.1g to a litre of water?


 If you want to and yes it's that simple. I don't bother because at 6.4+ ph there will be very little copper leeching. Just that slight amount is enough to buffer the water to 7.5 or above and no leeching is possible.


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## Northern_Monkey (Sep 11, 2018)

@TomHughes - As a bit of an aside, do you tip it upside down to empty fully every so often or tend to only top it up?

Might be worth trying the the above water composition advice, but maybe clear the boiler as well occasionally if you aren't already?


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## TomHughes (Dec 16, 2019)

Northern_Monkey said:


> @TomHughes - As a bit of an aside, do you tip it upside down to empty fully every so often or tend to only top it up?
> 
> Might be worth trying the the above water composition advice, but maybe clear the boiler as well occasionally if you aren't already?


 I wasn't doing that but I am now. 
It's due an overhaul so I may completely strip it once my classic is back together.


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## halo (Dec 14, 2016)

DavecUK said:


> If you want to and yes it's that simple. I don't bother because at 6.4+ ph there will be very little copper leeching. Just that slight amount is enough to buffer the water to 7.5 or above and no leeching is possible.


 Hi Dave,

For distilled water would you need to add bicarb and epsom salts?


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## Rob1 (Apr 9, 2015)

You don't need epsom salts or calcium chloride or anything similar to give hardness, just a source of bicarbonates will do. Using just sodium bicarb to get 40mg/l alkalinity you'll end up with about 25mg/l Sodium. You can use both sodium and potassium bicarb to limit sodium concentration to about 10mg/l but it's not as simple as a 50/50 split between the two. You could use hydroxide or carbonate sources and dissolve in the water with CO2 but that will require you to make a concentrate and add some of that to the brew water which is the most precise way to go anyway. Citrates can be used too but they are not good for standing water. Hydroxide can be dispersed by shaking well but it will settle if not turned into bicarbonate with CO2. Some people on home barista have used hydroxide for filter brews and report good results but there obviously the water standing in a reservoir isn't going to be an issue.


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## halo (Dec 14, 2016)

Thank you, Rob, for the clarification, really appreciated.


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## halo (Dec 14, 2016)

Rob1 said:


> You don't need epsom salts or calcium chloride or anything similar to give hardness, just a source of bicarbonates will do. Using just sodium bicarb to get 40mg/l alkalinity you'll end up with about 25mg/l Sodium. You can use both sodium and potassium bicarb to limit sodium concentration to about 10mg/l but it's not as simple as a 50/50 split between the two. You could use hydroxide or carbonate sources and dissolve in the water with CO2 but that will require you to make a concentrate and add some of that to the brew water which is the most precise way to go anyway. Citrates can be used too but they are not good for standing water. Hydroxide can be dispersed by shaking well but it will settle if not turned into bicarbonate with CO2. Some people on home barista have used hydroxide for filter brews and report good results but there obviously the water standing in a reservoir isn't going to be an issue.


 The reason I mentioned Epsom salts, was after reading this:

https://www.baristahustle.com/blog/diy-water-recipes-redux/

Would dissolving 1.68g of sodium bicarbonate to 1L of distilled water be enough?


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## Rob1 (Apr 9, 2015)

1.68g would be massively in excess of what would be enough....well, "enough for what?" I should ask but I assume some reasonable alkalinity.

Use the spreadsheet here to calculate what you need to add to x amount of water either to create a concentrate or to add directly to water for brewing with. You can also define how much of the concentrate to make and how much to add to any quantity of water for brewing and it will tell you how much of whatever additive you describe to add to the water for the concentrate.

https://www.coffeeforums.co.uk/topic/53491-non-scaling-water-calculator/?do=embed#comments


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## halo (Dec 14, 2016)

@Rob1Thanks for the link, I've posted over on that thread.


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## SupraMan (Mar 9, 2021)

Would green stains on a white towel be a sign that copper is leaching?


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