Why does the pH level in the boiler climb?

#1: Post by **okmed** » January 17th, 2014, 5:49 pm

I have a Bezzera Strega plumbed in with a water softener. The softened water has a pH of 7 (so does the city water before softening), KH of 90 ppm and GH of 40 ppm. I took a sample of the boiler water and it is 9 pH, 100 ppm KH and less than 20 ppm GH. Why does the pH go up ( becoming more alkaline) and should I be concerned ?

#2: Post by **TomC** » January 17th, 2014, 6:25 pm

okmed wrote:I have a Bezzera Strega plumbed in with a water softener. The softened water has a ph of 7 (so does the city water before softening), KH of 90 ppm and GH of 40 ppm. I took a sample of the boiler water and it is 9 ph, 100 ppm KH and less than 20 ppm GH. Why does the ph go up ( becoming more alkaline) and should I be concerned ?

Your pH is going up because more chemically pure H20 (as steam)is leaving the boiler than entering (fresh water), leaving behind higher concentrations of carbonates. They are buffers that raise pH (we use them in hemodialysis exactly for this reason, to buffer the acids and chemical wastes in the blood that the kidneys can no longer handle).

http://en.wikipedia.org/wiki/Carbonate_hardness

You can occasionally flush the boiler via the hot tap water to help mitigate this. I rinse all my paper filters off the hot water tap of my Strega just so that I'm purging more water thru the boiler, rather than just the tad bit used for extractions, and steaming.

January 18th, 2014, 10:58 am

Thanks for the response and explanation Tom. I do regularly drain water from the boiler to warm cups and make Americano's which is why I was surprised by the pH reading. I drained and refilled the boiler three times (testing after each refill) and still had a pH reading of 9 (my test kit only goes as high as 9 so I will have to find one that measures higher). This was time consuming and frustrating because I would have to wait for the boiler to heat the water back up to pressure to drain each time. I then got my little air compressor and used the steam wand to pressurize after each refill and then drain without having to wait for it to heat up. Eventually I got it down to a pH of 7. About four days later I tested it again and it was back up to 9 pH.
This is funny since I originally had a Claris water filter/softener and was concerned about the pH of 6 that it was delivering to my machine and it's affect on taste (and corrosion of copper) of the brew. I know this is not the case now with the brew since the softener I use doesn't change the pH but from what I understand a base can corrode just as an acid can. At what level of pH on the basic side should I be concerned about damage to the copper boiler?