Magnesium level in Severn Trent water

[Eric]

I bought a TDS meter when you replied to this last year and it has consistently been around the 250-290 level when I tested last year but today it was 158 but that was the first time I tested it this year.
Severn Trent are going to ring me on Thursday to discuss the water profile.

A single reading of your own has as much value as a water company's sample readings, they may be right only if their supply is consistent.

Water treatment for brewing isn't that complicated. If you want to be in control from the start, preadjust the level of alkalinity in your water to near that best suited for the type of beer you wish to brew. Pale beers require low, sometimes no alkalinity to avoid a too high mash pH, while beers with lots of dark and/or crystal malts will withstand or demand more alkalinity to avoid pH being too low.

Alkalinity in whatever form raises mash pH, and when mash pH gets too high, tannins and phenols will be extracted along with the sugars. If mash pH is too low, conversion of malt takes longer, potentially more than a standard period, and can produce a less fermentable wort to cause stuck fermentation.

Calcium has many beneficial influences like protecting enzymes from heat, depositing oxalates, phosphates and others while raising pH. Magnesium has similar influences to a lesser degree, but being more soluble is more influential during boiling than in the mash and also when little calcium is present. When used for brewing salts they will add sulphate and or chloride, both of which influence our perception of taste. Sulphate dries a beer which reduces the perception of malt type flavours, enabling hops to become more prominent, while chloride enhances malt type flavours, most especially kilned and roasted flavours. Pale ales are generally sulphate forward for hop influence and those with dark malts used for flavour rather than just a bit of colour are usually chloride forward. If you don't like the taste of beer, or prefer a softer taste, try calcium at 100ppm or less, otherwise get it above 100ppm.

It may be your supply is now ringed with other sources, this is becoming more commonplace. This can in some cases make it difficult to build exact profiles, but good brewing techniques will still produce a good beer.

[cc986]

I've just done another TDS reading and it is exactly the same as yesterday - 158. I also did another alkalinity reading and the level on the syringe was 0.74 which according to the Salifert table gives a dKh reading of 3.8. I multiply that by 17.9 (to convert to ppm) and I get 68.02.
Now, Brewfather does not let me add the alkalinity reading - it works it out from the bicarbonate level from what I can see - so if I manipulate the bicarbonate level until the alkalinity is 68, I discover that the bicarbonate level is 82. Which is a long way off anything that ST have ever given me.

[Eric]

Your conversion calculations on alkalinity are correct. Alkalinity as HCO3 (bicarbonate) = 1.22 X alkalinity as CaCO3.

Looking at the figures by your supplier, your water will vary significantly, but also there is no way that the given figure for hardness fits with the average figures for other major ions and worse, the reading you took with the Salifert kit today doesn't seem to fit either.

Have I got this right? Yesterday you took a TDS reading and measured alkalinity at 160 mg/l. Today the TDS meter reading was the same as before but alkalinity was 68mg/l. That can't be right, can it?

[MashBag]

Eric, on the subject of brewing salts... Do you add before or after boiling? Or put another way is the boil detrimental to DWB?

[cc986]

Your conversion calculations on alkalinity are correct. Alkalinity as HCO3 (bicarbonate) = 1.22 X alkalinity as CaCO3.

Looking at the figures by your supplier, your water will vary significantly, but also there is no way that the given figure for hardness fits with the average figures for other major ions and worse, the reading you took with the Salifert kit today doesn't seem to fit either.

Have I got this right? Yesterday you took a TDS reading and measured alkalinity at 160 mg/l. Today the TDS meter reading was the same as before but alkalinity was 68mg/l. That can't be right, can it?

That was my mistake. I don't think I had understood the calculation at that point. Also, I couldn't make up my mind whether the syringe reading was 0.77 or 0.78 and as the Salifert table doesn't show 0.77 I went with 0.78. I now know that the calculation should have been 3.2 dKh x 17.9 giving 57.28ppm. Had I gone with 0.77 the dKh would have been around 3.3 or 3.4 giving a ppm of 59 or 60.

If I boiled my water before brewing (which I used to do) wouldn't that at least partially remove the issue of fluctuating or unknown bicarbonate levels? I think I read somewhere that boiling for at least 30 mins reduces the level to around 30-40ppm. So even if I'm not sure what it starts off as, after boiling I could assume that it would be around 30-40ppm. Is that right?

[Eric]

Eric, on the subject of brewing salts... Do you add before or after boiling? Or put another way is the boil detrimental to DWB?

I use acid instead of boiling.

If you boil your water to reduce alkalinity, calcium carbonate will be deposited. The result is less calcium by an unknown amount and limescale deposit on the elements and/or vessel surface. By using acid, calcium level remains unchanged and depending upon the amount of acid used, the alkaline anion is replaced by a salt anion.

My water contains more sulphate than chloride like the OP's water, so mostly use hydrochloric acid and the bicarbonate that provides alkalinity is replaced by chloride. I also have sulphuric acid (for drier pale ales), phosphoric acid, and CRS. Phosphoric acid can leave a deposit of calcium phosphate, as boiling does. Using the other acids means the elements and boiler wipes clean with a soft cloth, sponge and warm water except for around the rim of the boiled wort.

I add salts to the grain or during the mash and recirculate or into the boiler.

cc986, alkalinity that low does not correlate with either the hardness given by ST, nor does it easily balance with the individual ion levels given. It matters not if the alkalinity measures 3 or 3.5 dKH, that seems to be about half the level for an ion balance.

I need more time to recheck my figures. You didn't just do a 2ml test rather than 4ml, did you?

[cc986]

No, defintely the 4ml test.

[Eric]

No, defintely the 4ml test.

It seems your water currently has less mineral content than given on the ST site.

ST's figures for 52 conductivity tests are less variable than are ion content, yet conductivity is usually an arithmetic function of ion content. I suggest they are more consistent with recording electronic meter readings than analysing mineral content of water, a problem you appear to be facing.

Did you record any early TDS meter readings you took? Those compared to the current reading of 158ppm (calibrated for common salt) would be of value.

It is possible to make a water profile with your TDS and alkalinity readings with the ST average figures, but it doesn't look at all practical even though it would be possible.

[cc986]

My TDS readings from last year were all between 249 and 292.

However, I have had two phone calls from them today and they agreed to run another report. This one was based on readings taken between 1st Feb - 16th Feb:
Calcium 51 Mg Ca/L
Chloride 32.1 Mg CI/L
Magnesium 9.21 Mg Mg/L
Bicarbonate (HC03) 157.84 mg/L
Sodium 37.5 Mg Na/L
Sulphate 57.7 Mg/L

So it looks like the Magnesium really has dropped from 42 to 9, but they were way off with the bicarbonate.

But even that is concerning because here is what they told me on 10th February (obviously within the same time frame)
Calcium - 69.6
Magnesium - 42.2
Sodium - 36.1
Chloride - 39.9
Sulphate - 70.2
bicarbonate - 212.4

[Eric]

That with 42.2 magnesium is impossible by a long margin. Reducing the magnesium to 12ppm provides a near balance. I think they might have a problem measuring magnesium.

The first profile has a reasonable ion balance and it isn't that far out from your TDS meter reading. What is out is your finding for alkalinity. Someone, I think it might have been Jocky, reported getting a Salifert kit that was well out of spec. and wonder if that is the cause of most of your troubles.

Do you have CRS, a calibrated 1ml syringe and kitchen scales? If so, weigh a kg of water and charge the syringe with 1ml of CRS/AMS. Stir the water well to release any surplus CO2, then add 0.3ml of CRS and stir vigorously again to complete the reaction and remove CO2 produced by the acid reacting with the alkalinity.
Take a small sample (1ml is more than enough) and add to it one drop of the Salifert indicator. If the sample goes pink after swirling, it likely contains less than 55mg/l alkalinity as CaCO3, 67ppm bicarbonate. If the sample turns blue, add a further 0.1ml to what remains of the kg of water and repeat the previous procedure. Continue until a small sample turns pink with a single drop of indicator.
When a sample turns pink and stays pink, multiply the volume of CRS in ml added to the water by 183 to get a measurement in mg/l that exceeds the amount of alkalinity in that sample.
If after 0.3 ml the sample is colourless or pink your Salifert reading is correct. If it happens after adding 0.7 ml of CRS, ST's latest figure for alkalinity seems to be correct.

[cc986]

Thanks Eric!
After the first 0.3 of CRS it turned blue. I repeated the process with another 0.1 of CRS and it turned pink. So, 0.4 x 183 = 73.2.

[Eric]

Thanks Eric!
After the first 0.3 of CRS it turned blue. I repeated the process with another 0.1 of CRS and it turned pink. So, 0.4 x 183 = 73.2.

So definitely a lower mineral level than ST advise.

If it's not too late, keep the sample that turned pink, and watch it for a few days in case there was excess CO2 present, in which case it will turn clear or blue.

[Jocky]

Yes I had the terrible Salifert kit.

It was the acid in the kit that was the problem, not the blue indicator reagent.

[cc986]

Thanks Eric!
After the first 0.3 of CRS it turned blue. I repeated the process with another 0.1 of CRS and it turned pink. So, 0.4 x 183 = 73.2.

So definitely a lower mineral level than ST advise.

If it's not too late, keep the sample that turned pink, and watch it for a few days in case there was excess CO2 present, in which case it will turn clear or blue.

I have kept the sample and will see what happens.

What does that test tell me - that the alkalinity is 73.2? If I put ST's values into Brewfather it says the alkalinity is 129. If I adjust the bicarbonate level down to 89 from STs 157 it shows the alkalinity as 73. Is that what I should do, or have I got that completely wrong!

[Eric]

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