A big ask...

[RustyHorn]

I'm a tad confused after reading my water report and was wondering if someone could help decipher the contents? It's not showing the minerals the same way as my EZ water spreadsheet does do I can't find what I'm looking for.
It's a big ask, but if you think you can help, and have the time, my water report can be found here: https://secure.thameswater.co.uk/water-quality-reports/2015 WQ Report_Z0265_kingston north.pdf

 

[Gnomebrewer]

This report isn't overly useful for brewing purposes, it's more about drinking water quality. We can get the following from the report though:

Approximate values (ppm):
Chloride = 50
Sulphate = 50
Hardness as CaCO3 = 250
Sodium = 32
(interestingly, they give a comment about the units for alkalinity, but don't report alkalinity).

From these, a few things can be deduced and estimated:

Ca (ppm) = Ca hardness / 2.5
Mg (ppm) = Mg hardness / 4 (approx.)
Because we only have total hardness, we can only get upper-values for these: Ca could be as high as 250/2.5 = 100ppm (if Mg = 0); Mg could be as high as 250/4 = about 60ppm (if Ca = 0). It is likely that Calcium is higher than Magnesium, but that there is some of each. You are likely to have between 50 and 100ppm Ca, and Mg between 0 and 30ppm.

You could also estimate your alkalinity by adding the mEq's of your Cations (assume all hardness is Ca and that there is no Mg...it doesn't affect the alkalinity calculation), subtracting the mEq's of your known anions (Chloride and Sulfate) to get the mEq's of bicarbonate. Your result will be in the moderate to high range (there are significant, but not massively high, amounts of any cation). However, you'd be better off contacting the water authority and asking specifically for the Calcium, Magnesium and alklalinity (or carbonate/bicarbonate) levels in your water.

 

[Gnomebrewer]

By my calculations (which may or may not be correct):

Cations (Ca, Mg, Na) = 100/40*2 + 32/23*1 = 6.4mEq/L (note - I'm ignoring the minor concentrations of other cations).
Anions (Cl, SO4) = 50/50*1 + 50/96*2 = 2.4mEq/L

We can assume the remainder is mostly due to bicarbonate, so there are about 4mEq/L of bicarbonate
4mEq/L HCO3 = 4*61 = 244ppm bicarbonate or
4mEq/L HCO3 = 4*50 = 200 alkalinity as CaCO3.

This puts you in the range of brewing dark beers, or adding acid for mid-range beers. You'll need to dilute (with RO water) or boil your water (to remove hardness and alkalinity) for lighter coloured beers. If you preboil your water, you should get down to roughly 60 to 80ppm bicarbonate (with a concurrent loss of 3mEq/L Calcium and/or Magnesium).

 

[ajdelange]

Gnomebrewer is on the right track.

First, the hardness in ppm as CaCO3 is the total positive ion charge less sodium, potassium etc. which are not picked up by the test. Other cations (iron etc will be picked up by it however) Thus total hardness of 250 implies a cation charge of 247/50 = 4.94 mEq/L. Add to that the charge on sodium which is 32/23 = 1.39 for a total cation charge (less potassium...) of 6.33. The total anion charge must equal this. The report gives us 51 mg/L for chloride. The equivalent weight of chloride is 35.15 so we have 51/35.15 = 1.45 mEq/L from that. Sulfate is reported at 51.8 and it has equivalent weight 46 for 51.8/46 = 1.12 mEq/L. The other anion of significance in nitrate at 26.4 mg/L. With its equivalent weight of 62 that's another 0.43 mEq/L. Sulfuric, hydrochloric and nitric acids are strong acids whose anions will not be protonated at pH 4.3 in the alkalinity test and which, therefore, will not be detected by the alkalinity test. We assume
1)That other strong acids (nitrous) are present in insignificantly small quantities
2)That all other acid (phosphoric, silicic, carbonic) anions plus hydroxyl ion will be detected in the alkalinity test.
Thus the sum of the known cations less the sum of the known anions must be the alkalinity:
6.33 - 1.45 - 1.12 - 0.43 = 3.33 mEq/L
Multiplying by 50 gives the alkalinity as 166.5 ppm as CaCO3

This is probably a pretty good estimate of the average alkalinity as the data on the other ions which are present in significant quantity (assuming I didn't overlook something) is quite complete. Potassium is the notable exception but probably insignificant because it is usually present at the level of a mg or 2 per liter and it has a pretty high equivalent weight (39).

But do take note that it is an average value. Examination of the ranges in this report suggest that the standard deviations are small meaning that this water is pretty stable over time.

To use this data with the typical home brewer's spreadsheet you will have to WAG the calcium and magnesium from the hardness. I would guess 2.5 mEq/L for each. Convert 2.5 mEq/L Ca++ to 50 mg/L (multiply by 20) and 2.5 mg/L Mg to 30 mg/L (that's kind of high so you might want to try a 2/3 - 1/3 split instead).

As you can probably deduce from the above discussion these problems are best dealt with using mEq but the writers of homebrewer's spreadsheets haven't figured this out yet. Therefore, most spreadsheets will ask that you specify the bicarbonate content. At your pH of 7.7 you can just multiply the alkalinity by 61 and use that (3.33*61 = 203.13). You are already subject to some error in making arbitrary assignments of hardness to calcium and magnesium and the error incurred by the programs in taking alkalinity data as bicarbonate will be small.

 

[RustyHorn]

By my calculations (which may or may not be correct):

Cations (Ca, Mg, Na) = 100/40*2 + 32/23*1 = 6.4mEq/L (note - I'm ignoring the minor concentrations of other cations).
Anions (Cl, SO4) = 50/50*1 + 50/96*2 = 2.4mEq/L

We can assume the remainder is mostly due to bicarbonate, so there are about 4mEq/L of bicarbonate
4mEq/L HCO3 = 4*61 = 244ppm bicarbonate or
4mEq/L HCO3 = 4*50 = 200 alkalinity as CaCO3.

This puts you in the range of brewing dark beers, or adding acid for mid-range beers. You'll need to dilute (with RO water) or boil your water (to remove hardness and alkalinity) for lighter coloured beers. If you preboil your water, you should get down to roughly 60 to 80ppm bicarbonate (with a concurrent loss of 3mEq/L Calcium and/or Magnesium).

Thank you for doing that for me
I did figure that my water would suit dark beers as it's Thames Water (London), which is the home of porter/stout. The London water profile can be found on brewers friend but I wanted to be sure of its accuracy. I'll email the water company again. They didn't reply last time.