Troubleshooting Bru'n water

[SEndorf]

Long time user. Normally within a couple points. But last several brews I'm way off.
Simple pale ale recipe:
11 lbs Rahr 2 row (adjusted to 5L pr BW notes)
4 lbs Bonlander Munich 10L (12.8SRM)
4 lbs White Wheat Malt 3L (3.3 SRM)
12 oz. Caramunich III 57L (76 SRM)

On the water adjustment tab, I calculate salts based on my mash of 8.25 Gallons.
In this case, for gram/gal:
0.40 Gypsum
0.25 Cal Chloride
0.40 Epsom
0.18 Lactic (1.50 ML)
Gives me Estimated Ph of 5.33

Using 100% RO water, I add all salts to HLT with exactly 20 gallons, (except lactic)
So I temporarily change the mash water volume to 20 and get:
8 Grams Gypsum
5 Grams Calcium Chloride
8 Grams Epsom

Transferred 8.25 gallons from HLT to mash tun and added 1.50 ML lactic
Readings at 15 min and 30 min were 5.13 and 5.18 respectively.

Using Milwaukee 102 meter tested and calibrated.
Can't figure out where I'm going wrong. Any tips appreciated.

 

[ScrewyBrewer]

I like to prepare my RO water, adding salts and acid, the night before brew day. In my mind this gives the water properties plenty of time to stabilize before being introduced to the grains during the mash.

On brewday I take pH samples cooled to ~75F at 30 minutes from the start of the mash. I realize I’m making more of an observation than giving an answer to a specific question. But I feel the consistency in water preparation and pH sampling routines at least eliminates those variables. And that is a good thing when it comes to predicting mash pH.

 

[Big Monk]

Long time user. Normally within a couple points. But last several brews I'm way off.
Simple pale ale recipe:
11 lbs Rahr 2 row (adjusted to 5L pr BW notes)
4 lbs Bonlander Munich 10L (12.8SRM)
4 lbs White Wheat Malt 3L (3.3 SRM)
12 oz. Caramunich III 57L (76 SRM)

On the water adjustment tab, I calculate salts based on my mash of 8.25 Gallons.
In this case, for gram/gal:
0.40 Gypsum
0.25 Cal Chloride
0.40 Epsom
0.18 Lactic (1.50 ML)
Gives me Estimated Ph of 5.33

Using 100% RO water, I add all salts to HLT with exactly 20 gallons, (except lactic)
So I temporarily change the mash water volume to 20 and get:
8 Grams Gypsum
5 Grams Calcium Chloride
8 Grams Epsom

Transferred 8.25 gallons from HLT to mash tun and added 1.50 ML lactic
Readings at 15 min and 30 min were 5.13 and 5.18 respectively.

Using Milwaukee 102 meter tested and calibrated.
Can't figure out where I'm going wrong. Any tips appreciated.

So you dose minerals for 20 gallons and only transfer the strike? Are you sure it was mixed well? You may be sending a disproportionate amount of the Ca and Mg salts to the mash tun and lowering the pH.

 

[SEndorf]

So you dose minerals for 20 gallons and only transfer the strike? Are you sure it was mixed well? You may be sending a disproportionate amount of the Ca and Mg salts to the mash tun and lowering the pH.

Good point but mixed well.
Electric system with constant recirculation. As the HLT heats to strike temp I stir often to prevent any settling of salts on the bottom.

 

[Silver_Is_Money]

Did you take your pH readings at around 75 degrees F., or did you take them at mash temperature?

 

[SEndorf]

I cool the sample to 68-70 F

 

[Silver_Is_Money]

Seems as if it should have mashed at right close to 5.4 pH.

 

[ScrewyBrewer]

I cool the sample to 68-70 F

@SEndorf when the predicted pH and the actual mash reading differ by 0.15 pH I'd consider that as being a win. Especially if that's your first time brewing this recipe.