Why is my effeciency getting worse?

[jacksonbrown]

When I first built my MLT cooler I was getting 85%-92% efficiency from my first five batches. Then it started dropping to the mid 70's. now I feel lucky if I hit 65%. My method hasn't changed. I've been using different base malts in different batches, so I can't see it being a single malt causing it. What in the world can be causing such a drastic drop over time the past 9 months?

 

[k1v1116]

grain crush is the first thing to check. Its possible your mill or the HBS mill is not tightened and the gap has been steadily increasing.

 

[lamarguy]

Does your thermometer need recalibrating? Mash temperature is critical. Are you tasting the spent grains to see if there are residual sugars not being rinsed well?

Have you checked the mash pH lately? Mash pH is critical and will change with city water fluctuations and different base malts.

Are you brewing bigger beers than in the past? If you're batch sparging, higher gravity translates to lower efficiency.

Has your crush changed? You may want to check the gap on your mill.

Just some things to check...

 

[jacksonbrown]

I check my mill every 4-5 brews to keep it consistent. I checked my thermometer today and it's still good (well, off by 2 deg which I already knew). I have not been checking my pH, but I 5.2, so I didn't think it was needed. I guess I can do that next time. I have brewed bigger beers, but I've also been doing standards (1.045-1.060). I guess it could be the city water. Although, I did make a batch with store bought spring water, and it was the same result. So, I don't know.

 

[BarleyWater]

What are you using for your MLT, and could it be possible that it is losing heat somewhere now that it wasn't before due to age and wear? If you mash temp is falling a lot throughout the mash, you could be missing out on some conversion.

 

[jacksonbrown]

It dropped 2 deg today from start to finish.

 

[bohdan987]

its a beat up grain mill, i am having same problem with a brew store mill! do you have own mill or you use store mill?
if you have your own mill, tune it up.
if you using a store mill, dont crush or buy grain from there(thats what iam doing)!
if store cant keep their grain mill in a desent shape, they should be in a buisnes.

 

[david_42]

Even though you've been checking your mill, I'd try reducing the gap for the next run. The running gap and the static gap may not be the same.