Originally Posted by mklojay
I did not have a pH meter to verify the mash pH. But shouldn't the chemistry of the water with the pale malt bring the ph down to the mid to low 5s?
No. You need to add acid for that traditionally in the form of sauermalz or sauergut. This is especially important with Pils as the water is soft (no pH lowering calcium) and the little bit of Carapils isn't that effective. See the Primer.
Unfortunately you did the opposite of what you should have done i.e. you added alkali in the form of bicarbonate. You added 400 mg icorresponding 400/61 = 6.6 mEq. Pilsner malt has buffering capacity of 25 - 45 mEq/kg-pH and you used 4.4 kg so that the buffering of the ash (from that alone) is 110 - 200 mEq/pH so your pH shift from the bicarbonate would be 0.03 - 0.06 which isn't too bad but it is in the wrong direction.