water treatment

When treating water, do you treat all the water ( ie ) 33 L  or just the mash water in my case that would be 17L leaving 16 L for sparge, I am using a grainfather.
I have read somewhere that you should test the mash wort for a ph reading and then add acid to bring down the ph if needed, this is the reason I’m asking about treating all the water or just the mash water,
Would it be ok to treat all the water and then test the wort for the ph, or would adding acid to the already treated water be a problem

I treat both mash and sparge water because the water I use is too high in pH and doesn't contain all the desirable minerals that I need for the styles I brew.

Before delving into manipulating your water, check out Bru'n Water. Read his water knowledge page, if you haven't already. He also has a spreadsheet you can use to calculate everything, but you'll want to know the mineral content of your water first. He offers a free spreadsheet. But if you make a small donation via PayPal, he'll send you a more up-to-date version that I feel works a little better than the free one.

Ultimately, you want to dough in and test the pH after 5 or 10 minutes. If it's too high, you can add lactic acid, test and remix. Fortunately, Bru'n Water can help you determine the amount of lactic acid to add. The latest version of Beersmith also does this, I believe.

many thanks for your reply, it seems that what your saying is on the same lines as I was thinking, just needed the confirmation, I have looked up Bru' n water and I will now give a donation thanks again for your help