Creating water recipes or concentrates is like dividing skill-points.
Like for KH you probably want something which works between 10-50 KH for filter coffee (20-60 KH for espresso)
So you have 10-50 skill-points to give, which you can split between NaHCO3, KHCO3, CaCO3, even Ca3C12H10O14 (calcium citrate) and Na3C12H10O14 (sodium citrate) if you have those.
At the lowest level you probably want at least 1ppm KH from NaHCO3 and on max level or slightly below max level, like Lv80 of 100 15ppm KH from NaHCO3 and 10ppm KH from KHCO3.
If you Buffer is on level 80 (or 100) you've put 15 skill points on NaHCO3 (+structure, +brightness +juicyness) and 10 skill points on KHCO3 (-acidity, +roundness, +chocolate enhancer)
Now you still have 25 of 50 skill points left you can divide on the other minerals.
And then you got the Skill tree for GH which is split into CaCl, CaSO, MgCl and MgSO where you have like 10 GH on Level 10 and 90-130 GH on level 100.
Like different water recipes are different classes wich are better or worse at certain skills and the coffee you're brewing is like the weapon you're equipping your character with. Some weapons will work better with some classes than with others.
And that's for concentrates.
Concentrates gives you flexibility.
Your coffee is too sour? Add more KH, your Coffee tastes boring and dull? add less KH, is it weak but you want a more intensive and juicy cup? Add more GH, or is it too much, too overwhelming and you'd prefer something more tea-like and delicate? Then add less GH.
It won't make.the perfect cup bit it will get you into the right direction.
If you wanna brew something for World Brewers Cup you have to tailor every mineral for GH & KH for a specific value which works best with the coffee you're brewing and your brewing recipe.
Ant if that's all too much just make some Holy Water which works great for 90% of all filter coffees.
I made a new water recipe which contains a base (5000g, 35GH/15 KH), buffer concentrate (90g, 1g/L = 5ppm KH) and booster concentrate (90g, 1g/L = 10ppm GH)
The base can be used without the buffer or booster, but I can add then to tailor my water if I need more KH to buffer acidity or if I want to enhance some fruity and floral notes via the booster. I thought about a good balancing between MgCl2 and MgSO4 for the buffer to add up to 100ppm GH to my water (but I still have to test how high I can go with the GH before getting bitter or salty tastes.
The Buffer minerals should also be balanced I guess, but I don't know at what amount Sodium Citrate starts to taste unpleasant yet(or adding unwanted citrus notes).
Buffer 5ppm/g KH
NaHCO3: 120ppm (0.202g)
KHCO3: 120ppm (0.240g)
C6H5Na3O7: 210ppm (0.618g)
Water: 90g
Booster 10ppm/g GH
MgCl2 : 600ppm (1.245g)
MgSO4 : 300ppm (0.739g)
Water: 90g
Base Water 35ppm GH/15ppm KH
CaCO3 10ppm GH/KH (0.050g)
CaCl2 15ppm GH (0.110g)
CaSO4 10ppm GH (0.086g)
NaHCO3 5ppm KH (0.042g)
Water: 5000g terracore
I can also make a concentrate for the base, but I have to shake or stir the crafted water up for a bit to dissolve the CaCO3 (which is mainly added to increase GH & KH without increasing Cl & SO, so I can get a bit higher ppm levels of GH/KH).