CRS dosage question

[SiHoltye]

Hello,

Am brewing tomorrow, and I'm not sure I'm using Graham's Wheeler's water calc right. The alkalinity info I have is this:

2008 to date Min Ave Max No.of test

Calcium 51.5 52.7 54.6 3

Magnesium 5.4 5.4 5.5 3

Total Alkalinity 52 82 117 121

(Please note, we measure alkalinity in mg/l HCO3, but multiplying the values by 1.6 converts them to CaCO3)

Sorry about the formatting. So I've input the 'ave' using the HCO3 selected and then the CaCO3 (HCO3 multiplied by 1.6) selected and it changes everything. What have I done wrong?

Anybody help?

 

[Aleman]

I've just had a look at my instructions, which say to use the value as CaCO3 so that is

82/1.219 = 67.

Now you want to reduce that to 25 . . . . and the important bit is that 1ml of CRS will reduce the alkalinity by 180mg so you need
(Total Alkalinity - Residual Alkalinity) * Vol To Be Treated
180

Which is ((67-25)/180)*35 = ( 42/180)*35 = 0.23*35 = 8.2ml of CRS

which is what there is in the second screen shot.

Personally I would put the converted figure of 67 in the alkalinity box AS CaCO3, then enter all my figures and with any luck they shouldn't change

Edit: I've revised the figures cause they looked a little high . . . and then discovered that to convert from HCO3- to CaCO3 you divide by 1.219 not multiply by 1.6 No idea where they got that from sorry

 

[SiHoltye]

Cheers Aleman,

The info about x1.6 for HCO3 to CaCO3 came from
xxxx xxxxxxx
Process Scientist
Sutton and East Surrey Water plc
Phone: 01737 785882
Fax: 01737 785865

Very kind of them to provide the info, but perhaps it should have been left at that though eh?

I made the correct additions concurring with your advice so thanks. Got 85% brewhouse efficiency, and 88% effiiciency by volume. What's best is after the last brew I planned for 85% so have the BU:GU correct this time