4th AG batch learned alot from the first 3. All of them had horrible efficiencies. I am able to explain them all and again I learned from the mistakes. My 4th went very well, 1 hour mash at 155. 173 deg sparge water. I fly sparged for 75 minutes. I got 6.5 gal in the BK. I used a refractometer and the gravity reading at the end was 1.010. So I am assuming I got most of the sugar out. Beersmith says OG should be 1.064. I did a 105 minute boil and was left with 5 gallons. The problem is my OG is 1.049. I read it with the hydrometer and with the refractometer and they both said the same thing. The only thing that was different is I used some phosphuric acid to lower the pH in the HLT before I heated and sparged. If my sparge water has too low a pH can it effect efficiency???