Help with low efficiency

[u/BlizardLizardWizard]

Hi,

I've been brewing for a bunch of years now, but more recently started actually calculating out my efficiency for all grain brews. I've noticed that for the few I've done this for, my calculated efficiency has been unexpectedly low. I was hoping r/homebrewing might be able to help me figure out why.

As an example, my most recent recipe was a DIPA. I used 12lb pearl malt, 1lb wheat, 1lb, caramel 20L.

Mash water: 14lbs/grain x 1.4qt/lb = 4.9 gal
Water temp: 167F
I preheat my mashtun (large blue Igloo) with 175F water, which I then discard.
I add the 167F water to my mashtun and slowly stir in the grain.
Temp check reads 154F.
Steep 120 mins. Temp remains relatively stable, but at 85 mins, the temp dipped to 148, and I added 1/2 gal 175F water to bring it back up to 151F. Temp check at mashout was 149.5F.
I vorlauf and lauter, then fly sparge with 170F water to bring the pre-boil volume to 7 gal.

I measured a brix of 11.1 with a refractometer, which I converted to a gravity of 1.048.

Efficiency Calculation:
PPG = (Vpreboil x gravity points)/lbs grain = (7gal x 48)/14lbs = 24
Efficiency = PPG/PPGmax = 24/37.7 = 64%

I used table on typical malt yields in How to Brew to estimate the PPG max.

Wondering if it's the extra 1/2 gal used to temp adjust or if I'm not calculating the value correctly. Any input is appreciated.

[u/Indian_villager]

As others have mentioned, there are a heap of knobs for efficiency.

1) Crush - Easily your biggest knob, Morebeer will crush a little wide so that all the newbies who didn't invest in rice hulls aren't complaining about stuck mashes.

2)Water volumes - Run your mash a little thicker, this way you move more water to the sparge volume to rinse the grains off.

3) Mash pH - I have had better efficiency by targeting 5.4-5.5 as measured at room temperature.

4) Sparge technique - There are some folks who will argue that you need to constantly maintain 1" of liquid above your grain bed. I will completely argue against this. Before you introduce your sparge water drain off wort until the very tops of the grain is peaking out, I mean barely 2mm of grain sticking out. Then while draining, fly sparge in your sparge water until you are about 1/2" above the grain bed. Stop your sparge water, and let the very top of the grain bed peek out again. From here sparge normally. What this does is to prevent what is essentially a serial dilution in that headspace above your grainbed, this way you are boosting the concentration gradient between your grain bed and your sparge water. Then once you get half of your preboil volume collected in your kettle, pause the mash tun outlet and the sparge water inlet for 3 mins. After that rest, continue sparging as normal. With all this I am still able to sparge out in 20 mins for a 5 gallon batch, and I am regularly in the upper 80s for total brewhouse efficiency.