Brupaks AMS Carbonate Reducing Solution (previously known as CRS) is a water treatment solution specifically designed to reduce the hardness and alkalinity of water to be used in full grain brewing and is used as an alternative to having to boil the liquor to drive out the dissolved carbonates.
The amount to be used will depend upon the hardness and alkalinity of your own source water (this information can be obtained from your local water authority) and the type of beer being brewed. A full description of the major constituents in brewing water and their importance to the brewing process is available on the website of "Murphy and Son", the manufacturers of AMS, DWB and many other chemicals and additives used by the brewing industry, and can also be downloaded HERE.
The following material, quoted from the Brupaks website, explains how CRS should be used:
"Before you can start to treat your water you should first contact your water supply company and request the total alkalinity of your water in p.p.m. Unfortunately this is not as clear cut as it should be. Water authorities usually express alkalinity as HCO3 (hydrogen carbonate) whereas the brewing industry uses the traditional CaC03 (calcium carbonate). To use the tables below you will need to know the alkalinity expressed as CaC03. As you will probably have only the HC03 value, you can convert it to CaC03 simply by dividing this figure by 1.22. From this figure it is possible to determine the required amounts of CRS and DLS to be added for all styles of beer. An average Bitter or Pale Ale requires the water to have a total alkalinity of 30-50 p.p.m. and a calcium content of 180-220 p.p.m. If the total alkalinity of your water is below 50 p.p.m. you will not need to use CRS but will most probably need to increase the calcium with DLS.
Example: You are brewing a Bitter and the total alkalinity of your water as CaC03 is 195 p.p.m. In order to bring it within the target range of 30-50 p.p.m. you will need to reduce the alkalinity by 145-165 p.p.m. From the following table you can calculate the amount of CRS to be added. N.B. All brewing liquor should be treated with CRS, not just that used for mashing.
CRS in millilitres per litre
The table shows that to reduce the alkalinity by 160 p.p.m. CRS should be added at a rate of 0.87ml per litre. Thus for a standard 25 litre brew, which will probably require 30 litres of liquor, 30 x 0.87 = 26mls of CRS should be added. After adding CRS, several minutes standing time should be allowed to release the carbon dioxide produced by the neutralisation of the excess acid.
Now that the carbonate level has been adjusted, you now have to correct the calcium content. Fortunately a close approximation of the amount of calcium present can be obtained by a simple piece of arithmetic:
Original alkalinity in ppm x 0.4 = Calcium in ppm
In the above example you have an original alkalinity of 195 p.p.m. Using the above formula the calcium content can be calculated as follows: 195 x 0.4 = 78 p.p.m.
A typical Bitter requires a calcium content of 180-220 p.p.m. As you already have 78 p.p.m. you will need an extra 102-142 p.p.m."
These are the recommended alkalinity and calcium levels for the most common beer styles.
Bitter and Pale Ale. Alkalinity as CaC03 - up to 50 p.p.m. Calcium - 180 to 220 p.p.m. Mild Ale. Alkalinity as CaC03 - 100 to 150 p.p.m. Calcium - 90 to 110 p.p.m. Porter and Stout. Alkalinity as CaC03 - 100 to 150 p.p.m. Calcium - 100 to 120 p.p.m. Pale Lager. Alkalinity as CaC03 - up to 30 p.p.m. Calcium - 100 to 120 p.p.m.
The Calcium levels are adjusted by adding Brupaks DWB powder, formerly known as DLS.
A full explanation of the the procedure, and details of other Brupaks products that may prove useful, can be found on the Brupak website or in this AMS technical Information sheet available from Murphy's website.
After adding the CRS solution, the liquor should be left for a few minutes prior to use to allow any CO2 produced to disperse.