Brew Water for Czech Pilsner

Hey everyone! I plan on brewing a czech style pilsner tomorrow which will be my first lager... I have the fridge all set up and ready to go with a temp control unit. I also figure that this is an appropriate batch to take water quality into effect for the first time. I just got a local quality report for my location, San Luis Obispo, CA. Here it is:

Ca++= 40ppm
Mg++= 35ppm
Na+ = 30ppm
HCO3- = 240ppm
SO4- = 70ppm
Cl- = 25ppm
Hardness= 240ppm

And John Palmer's report on pilsen's water is:

Ca++= 10ppm
Mg++= 3ppm
Na+ = 3ppm
HCO3- = 3ppm
SO4- = 4ppm
Cl- = 4ppm

I was wondering what the general consensus is for what I should do to change my quality to imitate that of pilsen. I will be brewing an all grain batch and will use about 8 gallons total of water. Based on beer tools water chemistry calculator I was just going to use 7 gallons of Deionized water and one gallon of local tap water. What do you think?

That's exactly the route i would start out with. I'd probably be inclined to increase the numbers a little more for yeast health - at least the Ca (target 20-30ppm).

Thanks. I ended up doing what I said before in addition to adding 7 grams of calcium carbonate to drop my mash pH significantly.... Hopefully this works.

How did this Pilsner turn out? I want to do one and I have been afraid that if I went with Palmer's numbers the yeast would not Flocculate.

nathanmunn said:

How did this Pilsner turn out? I want to do one and I have been afraid that if I went with Palmer's numbers the yeast would not Flocculate.

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You need to add Ca+. Yes, those are traditional Pilsen water numbers but it's way too low in Ca+ to mash modern malts with basic techniques. The historical Czech pils were mashed with four step decoctions with an acid rest to keep the pH down and extended low temperature rests to help convert the under-modified malt. Simple answer is to keep the CO3 and SO4 levels way down and use a calcium chloride addition to get your Ca+ number up to 50-75ppm.