I have been doing no sparge brews lately and I have been figuring the water additions but putting the whole volume of the mash water in the mash water volume field or split it up between the steps? i.e. does total mash volume include the all infusions?
The details
40 liters kolsch
18 lbs pils
2 lb munich
all RO water
35 liters first step
25 liters mashout
I was going to prepare all the water at the begining adding
If all of the water is going into the mash tun initially, then you should enter it that way in Bru’n Water. The RA of the water interacts with the malt acidity to estimate a mash pH. There is no advantage to entering a portion of the water as a sparge addition unless you are actually doing it that way.
I didn’t catch the fact that you are stepping. In that case, I recommend that you consider only the initial infusion as the mash volume. I assume that the first temp step is a sachrification rest. The later mash out step should be treated as a sparge addition.
The reason I recommend focusing on that first step and its water profile is that this initial step is when most of the starch conversion occurs. Get this step where you want it to promote the fermentability you want.
Given that it is only the amount of minerals in the water that affects pH (to a first order at least) you should be able to add all salts to the mash/strike water. The addition of more low mineral RO water will not change pH by much.