Troubleshooting Common Homebrew Problems — Causes and Fixes

Why is my home brew not fermenting?

If there's no airlock activity after 48 hours, the most likely cause is temperature — below 15°C and most ale yeasts are inactive. Move your fermenter to a warmer location (18–24°C is ideal). Also check the lid is properly sealed and the airlock is correctly filled with water. If temperature isn't the issue, pitch a fresh sachet of Gervin GV12 Ale Yeast or use GV7 Restart Yeast.

Why is my home brew beer flat?

Flat bottles are almost always caused by: fermentation wasn't complete when bottling, insufficient priming sugar, or crown caps not fully sealed. Always confirm fermentation is done with a hydrometer before bottling. Use one Carbonation Drop per 500ml, and check caps are fully crimped. Condition at room temperature for at least 2 weeks. See our conditioning guide.

Why is my home brew cloudy?

Cloudiness is usually yeast still in suspension, protein haze, or chill haze. Add Young's Beer Finings 48 hours before bottling and cold crash if possible (2–4°C for 48 hours). For future batches, add Protafloc Tablets in the last 15 minutes of the boil to prevent protein haze forming.

Why does my home brew taste like vinegar?

A vinegary taste is bacterial contamination — specifically acetobacter converting alcohol to acetic acid. This is caused by insufficient sanitation or oxygen exposure during fermentation or transfer. Unfortunately there's no fix once it's happened — the batch should be discarded. Use Young's Steriliser on every surface that contacts your beer, every time. See our sanitation guide.

Why does my home brew taste cidery or of apples?

Cidery or green-apple flavour is acetaldehyde — a fermentation byproduct yeast cleans up with sufficient time. It usually means the beer was bottled too early, fermented too warm, or used too much plain white sugar. Condition in the bottle for at least 3 weeks. For future batches, replace plain sugar with Brew Enhancer 2. See our Brew Enhancer guide.

Why is my home brew fermentation stuck?

A stuck fermentation (gravity stopped above expected FG) is most commonly caused by low temperature or nutrient deficiency. Warm the fermenter to 20–22°C and wait 48 hours. If it still doesn't restart, add Gervin GV7 Restart Yeast with a teaspoon of Yeast Nutrient. Always confirm with a hydrometer before concluding fermentation is stuck.

Why are my bottles over-carbonated or gushing?

Over-carbonation means fermentation wasn't complete when bottling, too much priming sugar was used, or bottles were stored too warm during conditioning. Check your FG with a hydrometer before bottling every time — this is the single most preventable home brew problem. For future batches, use Carbonation Drops (one per 500ml) to eliminate measuring errors.

For answers to more common questions, see our complete home brew FAQ. Browse home brew equipment and ingredients at BrewCo UK.