To fully diagnose efficiency issues, the following measurements are needed:
- Grain bill weight
- Strike water volume (everything prior to initial run off)
- SG of wort at end of mash, or first runnings SG
- Sparge process (fly, batch, none)
- Sparge water volume (for each batch sparge if more than one)
- Pre-boil volume
- Pre-boil SG
- Weight & type of any sugar added to the boil
- Post-boil volume
- Post-boil SG (OG)
- Volume into fermenter
Accurate measurements are critical, since the efficiency calculations cannot be better than the measurement accuracy. All volumes should be corrected for thermal expansion to 68˚F, or the volume measurement temperature reported, so that corrections can be made. Hydrometer measurements should be taken with the wort temp within 20˚F of the hydrometer's calibration temperature, and then corrected for the temperature at which the measurement was made.
Mash Efficiency = Conversion Efficiency * Lauter Efficiency
Brewhouse Efficiency = Mash Efficiency * Fermenter Volume / Post-boil Volume
With the measurements listed above, all of the factors in the above equations can be calculated. Conversion efficiency should be greater than 95%. Lauter efficiency is a function of sparge process and grain weight to pre-boil volume ratio, and maximum achievable can be predicted (but not as accurately for fly sparge.) Once you know which efficiency factor is lower than what should be achievable, then you know what part of your process needs to be addressed.
If your efficiency is really as low as 30% (and there is no way to double check that since none of the information above was supplied) you are almost certainly having problems with conversion. It would be very difficult to lauter poorly enough to explain that low an efficiency.
Too coarse a crush is very often the major problem with conversion efficiency, but even with poor crushes, brewers can get 50% - 60% efficiency or higher. So you must have something contributing besides just crush.
Mash temperature being way off (due to an uncalibrated thermometer) is one likely cause. Check your thermometer's readings in boiling water (should be 212˚F, unless you are at high elevation), and in a glass
full of crushed ice with little water (should be 32˚F.)
Mash pH could be contributing to lower conversion efficiency. What is your water source, and do you have a mineral and alkalinity report for it? Are you doing any mineral or acid additions to your water, and if so, how are you determining what you add?
With more information, the HBT community should be able to recommend more specific actions to improve your efficiency.
Brew on