Troubleshooting Brew Day Problems

Problems Happen

Even experienced brewers encounter problems on brew day. Knowing how to diagnose and fix issues in real time saves batches and reduces frustration. Here are the most common problems and their solutions.

Stuck Mash

Symptoms: Wort stops flowing from the mash tun during lautering. The grain bed has compacted.

Causes: Too-fine crush, high percentage of wheat/rye/oats without rice hulls, draining too fast (excessive suction).

Fixes: Gently stir the top inch of the grain bed. Slow the drain rate. If it persists, underlet by gently pushing water up through the false bottom to re-float the grain bed. For future batches, add rice hulls (5-10% of grain weight) and adjust your mill gap.

Missed OG (Too Low)

Symptoms: Pre-boil or post-boil gravity is lower than the recipe target.

Causes: Poor mash efficiency (incorrect temperature, crush, or water ratio), short sparge, volume overshoot.

Fixes: Extend the boil to concentrate the wort (each additional 15 minutes reduces volume by about 0.5 gallon). Add DME — 1 pound of DME per 5 gallons raises OG by approximately 0.008. For future batches, check your crush, verify mash temperature with a calibrated thermometer, and adjust grain quantities.

Missed OG (Too High)

Symptoms: Gravity is higher than the recipe target.

Causes: Over-sparging, under-estimating evaporation, too much grain.

Fixes: Add water to dilute to the target gravity. This increases volume, so ensure your fermenter can hold the extra.

Boil-Over

Symptoms: Wort erupts over the kettle rim when reaching a boil or when adding extract/hops.

Fixes: Immediately reduce heat. Spray the foam with cold water. Lower the kettle off the burner. Once controlled, resume at a lower heat setting. Prevent by leaving 25% headspace in the kettle and watching closely during the first 10 minutes.

Slow Cooling

Symptoms: Wort takes more than 30 minutes to reach pitching temperature.

Fixes: Add more ice to the ice bath. Pre-chill cooling water by running it through a coil in an ice bucket. Stir the wort gently while chilling (movement improves heat transfer). Invest in a proper wort chiller for future batches.

Fermentation Does Not Start

Symptoms: No airlock activity or visible krausen 24-48 hours after pitching.

Causes: Yeast viability issues (expired, under-pitched, killed by hot wort), insufficient aeration, fermenter lid not sealed.

Fixes: Check the fermenter seal first. Take a gravity reading — fermentation may be occurring without visible signs. If gravity has not changed, pitch fresh yeast. Ensure wort was below 80 F before pitching.

Off-Aromas During Fermentation

Symptoms: Sulfur (rotten eggs), banana, solvent, or butter smells from the fermenter.

Causes: Temperature too high (fusel alcohols, excessive esters), yeast strain character (some produce sulfur normally), or stressed yeast.

Fixes: Lower the fermentation temperature by 2-3 degrees. Be patient — many off-aromas clean up during conditioning. Sulfur is common with lager yeast and usually dissipates.