another_jim wrote:, it doesn't add up.

On the other hand, if the Chicago water board can't even do the sums; it's no wonder that people overestimate the scaling potential of their water.

Tap Water
TDS Meter (HM 3): 160
API KH: 107
API GH: ~150

The titration tests have a swing of +-18.

This looks to line up with the hardness and TDS levels reported by the Chicago Board.

Peppersass wrote: I could have sworn I read somewhere that the TDS doesn't necessarily equal the sum of the hardness and alkalinity, but maybe I just dreamed that.

I remember reading the same thing but can't locate the source.

Looks like I'm the one with the unit problems.

All the tests report TDS, hardness, and alkalinity in CaCO3 equivalent units. Apparently, when water is composed entirely of CaCO3 and MgCO3, will get you TDS = GH, and KH = 2/3 * GH. This is in line with everyone's testing.

I did my titration tests years ago when I wrote the FAQ; and only got the TDS later. I misunderstood how the results converted. Thanks for setting me straight.

TDS meters are a lot easier and cheaper then strips or titration, so it's useful to have a rough (but unbiased!) estimate of GH and KH from TDS in natural water.

Damn, I think I need some caffeine 'cause you guys are giving me a headache, lol. I'm glad I have just a pour-over machine. I buy the purified bottled water that says "minerals added for taste," and I'm good to go.

I have a very adventurous spirit.

I enjoy understanding all things related to anything

brianl wrote:I enjoy understanding all things related to anything

Ha, ha...not an undertaking to be taken lightly when it comes to espresso...the variables seem endless sometimes! Headache notwithstanding, an interesting read end-to-end.

So, for the many years I've been making espresso at home, I have known that water mineral content an pH are very important, but have just recently began to look carefully at what I'm using, and trying to understand it as much as I need to to be a self-sufficient analyst of my own maintenance needs. I'm definitely not there yet. I started with defaulting to the bottled crystal geyser water, then went for in reservoir ion exchange cartridges, to doing GH & KH tests on my filtered water from my refrigerator...and finally to installing a Mavea Purity system from CCS when I remodeled my espresso bar and plumbed in my machine.

I now have enough stuff to test my water (pH titration kit, GH/KH kit, and a TDS meter) at least the basics at least. I haven't tested the pH yet, and my TDS meter is new to me, but I've been using the API GH/KH kit for about 2 years.

(as you can see, I've since tested the pH)
Mavea water is: (at room temp of 71F)...GH 35.8ppm, KH 107.4ppm, TDS 180, pH = 6.4
Tap water: (also at room temp of 71F)...GH 71.6ppm, KH 214.8ppm, TDS 274, pH = 7.6

I know I'm about due for a replacement cartridge for the Mavea, but I don't really know what to do with the results otherwise. I guess I need to do math and figure out the scale potential, and I do want to run the pH titration...but I'm curious if anyone can dumb it down for me. As much as I want to get a good handle on this, I've kinda had my fill of math and science over the years, so having to crunch numbers takes the fun out of it for me.

OK, so, I'm not as lazy as I thought I was...

I measured my tap water GH, KH and TDS, and also measured the pH of both the tap water and the water feeding may machine via the Mavea. Results above...
crunching both sets of numbers through the LI equation in Jim's Insanely Long...

Mavea water is -8.393...
Tap is -0.208...

Seems like I can decrease the bypass setting on my Mavea without much worry about scale build up, and thereby improve the taste of my espresso. Or maybe I should put a charcoal filter between my Mavea and my machine? As far as I can tell, what would be optimal would be to increase the GH without increasing the KH (or even better while simultaneously slightly lowering the KH). However, before I do anything, I intend to perform all the tests on the water from my group and my hot water wand.

Useful comments anyone?

another_jim wrote:All the tests report TDS, hardness, and alkalinity in CaCO3 equivalent units. Apparently, when water is composed entirely of CaCO3 and MgCO3, will get you TDS = GH, and KH = 2/3 * GH. This is in line with everyone's testing.

Are you saying that when water is composed entirely of CaCO3 and MgCO3, the alkalinity is always 66% of the hardness? That's not in line with my tap tap readings, where all three are within 10%-20% of each other. Would that indicate the presence of other minerals that increase the alkalinity?

That said, in my case the %TDS measurement is close enough to the hardness that it does serve as a good measure. This is handy.

But that only holds true for my tap water. The %TDS of my softened water roughly approximates the alkalinity but not the hardness, which is zero. But I guess that water doesn't meet the definition of being composed entirely of CaCO3 and MgCO3.

The 2/3 was my impression looking at the long list of mineral waters. However, carbonates are the overwhelmingly most common anion in natural water; calcium and magnesium are also common cations, but so is sodium and potassium. If the latter are a significant percentage of the cations in the water, they will take up their share of carbonates. This means there will be extra carbonates that the Na, Ka cations are binding, rather than the Ca and Mgs.