The recommended level of copper intake is 0.9 milligrams per day for adults (according to NIH https://ods.od.nih.gov/factsheets/Copper-Consumer/)
So if you drink five espressos per day, or 200 grams, and with a copper level of 0.5 ppm in the brew water, you would get 0.1 milligrams from your coffee, which is very small compared to the 0.9 milligrams. In other words, you should be able to use the aquarium test, with a resolution of 0.25 ppm, to see if you have to worry about your copper intake from espresso.

... assuming that you do not eat any food at all or drink any other fluid .

Regardless, it is repeated low-level exposure that more likely matters from a health perspective. Will one cigarette a day kill you? How about five a day? Twenty? Or maybe just some second-hand smoke? The absolute amount of contaminants per dose/cigarette is negligible. One cigarette won't kill you, but your odds of disease and premature death go up after repeated exposure.

FWIW, copper vessels in and of themselves are safe for most folks, and I am not saying that a copper boiler or tube is unsafe. Vessels made with lead (crystal glassware) or aluminium (cookware) are also safe. It is how one uses those vessels that determines safety.

The OP has some condition related to copper exposure. That is different from the risk of copper exposure to folks generally (population). Generally, conditions related to exposure to a specific (usually heavy) metal are related to an individual's inability to get rid of excess intake - so the treatment, in part, is to reduce intake. For example, people with hemochromatosis (iron retention) are advised not to use cast iron cookware, eat foods high in iron, etc.

What? What is six nines ?

Makes sense. Again, given how popular coffee has been in recent history together with the use of copper, I'm surprised that we don't have this info already.

baldheadracing wrote:... assuming that you do not eat any food at all or drink any other fluid .

No, the example was constructed to give you 11% (0.1/0.9) of the daily recommended intake via espresso. To saturate the recommended intake you would need to drink 1.8 liters of espresso per day with the numbers I used.

Ah. My apologies, I failed to understand your math .

Rob101 wrote:What? What is six nines ?

99.9999%

Btw, you own a La Pera? How much for one of those? Are they still making them? How do you like it? And hiw does it compare to a higher end profitec, Elektra, etc?

Yes. Currently $12k. Yes. I like it. It costs more .

I/ve seen other posts where people have actually tested, using copper home tests kit and assuming they detected anything over .25mg/litre, it was undetectable. We have to remember that coffee has copper naturally present in it. and brewing ,method affects copper levels, i.e. French press, vs drip vs espresso. 've seen some studies published in ncmbi on copper levels in coffee and espresso was insignificant. So the rest would be to measure level of copper in water before going into machine and comparing to water coming out at the group hear and at the water wand to see if machine adds anything. If most sensitive home tests detect anything over .25mg / litre, then it appears to be pretty insignificant.