Troubleshooting Playbooks

Step-by-step playbooks for the most common brewing problems, with root-cause decision trees, immediate containment actions, and next-batch prevention.

This page provides structured diagnostic playbooks for the most common brewing problems. Each playbook covers: how to confirm the problem, likely root causes in order of probability, immediate containment actions, and changes to make next batch.

For off-flavor diagnosis, also see Quality Control & Off-Flavor Diagnostics.

Brewfather Tip: Brewfather's batch Readings log (gravity, temperature, notes) and batch step annotations create a timestamped record that makes many of these diagnoses straightforward. Consistently logging OG, fermentation temperatures, and FG readings will let you quickly cross-reference against these playbooks.

---

Playbook 1: Low Mash/Brewhouse Efficiency

Confirm the Problem

• Measured OG is significantly below target OG (>3–5 points on specific gravity scale, e.g., measured 1.042 vs target 1.050).

• Pre-boil gravity is also below target.

Decision Tree

Is pre-boil volume higher than planned?
  → YES: Volume dilution is the cause. Boil longer to reduce volume and concentrate wort.
  → NO: Continue...

Is the grain crush adequate (husks mostly intact, endosperm well broken up)?
  → NO: Adjust mill gap (often ~0.9–1.1 mm for many two-roller mills; tune to your system).
  → YES: Continue...

Did conversion complete? (Iodine test: no blue/black = conversion complete)
  → Starch present (blue/black): Mash temp too low (<62 °C / 144 °F) or time too short.
  → YES, conversion complete: Continue...

Is mash/sparge pH and sparge temperature controlled?
  → Runoff pH rising toward/above ~6.0 and/or very hot sparge water: higher tannin extraction risk.
  → Mash pH >5.8: beta-amylase activity and fermentability can suffer.
  → Continue...

Is grain bill measured by weight, not volume?
  → Volume measurements of grain are unreliable. Always weigh.

Immediate Actions (Current Batch)

1. If pre-boil volume is high: extend boil time to increase gravity through evaporation.

2. If wort is in fermenter at low OG: add dry malt extract (DME) dissolved in boiling water and chilled; add to fermenter and mix well before pitching. (Calculate: ~0.45 kg / ~1 lb DME per 20 L raises gravity approximately 8–9 points.)

3. Note measured OG in Brewfather batch readings — yeast pitch rate calculations depend on actual OG.

Next Batch Prevention

• Calibrate and adjust grain mill; test crush visually.

• Verify equipment profile in Brewfather is accurate (mash tun dead space, trub loss, boil-off rate) — Brewfather uses these values to calculate expected efficiency.

• Perform iodine conversion test at 60 minutes.

• Check and correct mash water chemistry (target pH 5.2–5.4).

---

Playbook 2: Stalled or Stuck Fermentation

Confirm the Problem

• No visible airlock activity for 48+ hours when fermentation appeared incomplete.

• Gravity reading same as previous reading taken 24–48 h earlier.

• Gravity is significantly above target FG (>5+ points).

Important: Always confirm with a gravity reading. Airlock activity alone is not reliable — airlocks can leak or activity can slow while fermentation continues.

Decision Tree

Is the temperature within the yeast's recommended range?
  → NO (too cold, <15 °C / 59 °F for most ale yeasts): Warm to proper range.
  → YES: Continue...

Was the pitch rate adequate?
  → Under-pitched: Add a fresh, actively fermenting starter or re-pitch with fresh rehydrated dry yeast.
  → YES: Continue...

Was wort properly oxygenated before pitching?
  → NO: You cannot fully undo this now; focus on temperature control, gentle rousing, and (if needed) re-pitching healthy yeast.
  → YES: Continue...

Is the gravity stuck near the target FG?
  → YES (within 2–3 points): Fermentation may be complete; confirm with consistent readings 24 h apart.
  → NO, well above target: Continue...

Is the wort likely low in fermentability (e.g., very high mash temperature, high crystal/dextrin malt load)?
  → YES: You may be near the practical FG for this wort; verify recipe assumptions before aggressive intervention.
  → NO: Consider re-pitching with a healthy, beer-appropriate yeast strain with adequate attenuation for the style.

Immediate Actions (Current Batch)

1. Warm the fermentation vessel to the high end of the yeast's recommended temperature range (or a few degrees above).

2. Gently rouse the yeast cake by carefully swirling the fermenter — this can re-suspend settled yeast.

3. If stuck after 24–48 h of warming and rousing: re-pitch with fresh, active yeast (starter or properly rehydrated dry yeast) matched to the beer.

Next Batch Prevention

• Calculate and achieve adequate pitch rate (Brewfather's Yeast Calculator tool estimates cells needed based on OG and volume).

• Oxygenate wort: ~8–10 ppm DO for ales; ~10–12 ppm for lagers and high-gravity beers.

• Control fermentation temperature during first 48–72 h.

---

Playbook 3: Haze (Unintended)

Confirm the Problem

• Beer is cloudy when clarity was intended.

• Haze persists beyond normal cold-crashing time or is not style-appropriate.

Decision Tree

Does haze clear when beer is warmed to room temperature?
  → YES: Chill haze (reversible protein-polyphenol complex). Cosmetic issue only.
  → NO: Continue...

Was beer cold-crashed (0–4 °C / 32–39 °F) for 48–72 h?
  → NO: Cold crash first, then reassess.
  → YES: Continue...

Does the beer taste off (tart, musty, medicinal)?
  → YES: Biological haze (contamination). See Playbook 6 (Contamination).
  → NO: Continue...

Is there visible particulate/floating matter (vs. uniform cloudiness)?
  → YES: Likely yeast in suspension. Increase cold-crash time or use a fining agent.
  → NO: Continue...

Was Irish moss/Whirlfloc added at the end of the boil?
  → NO: Lack of kettle finings allows more protein into fermenter.
  → YES: Continue...

Was a whirlpool performed after boil to separate trub?
  → NO: Large trub carryover contributes to persistent haze.
  → YES: Protein/tannin haze likely; consider fining agents.

Types of Haze Summary

Haze Type	Characteristics	Solution
Chill haze	Clears when warm, returns when cold	Gelatin or silica gel fining; extended cold conditioning
Yeast haze	Uniform cloudiness; yeast-like aroma	Cold crash; gelatin or isinglass fining
Protein haze	Persistent; may be fine/silky	Reduce mash temperature slightly; add Irish moss at boil; cold conditioning
Biological haze	Off-aroma/flavor present	Contamination — see sanitation guidance
Starch haze	Follows incomplete conversion	Confirm conversion with iodine test; extend mash time

Fining Agent Quick Reference

Fining	Use Stage	Notes
Irish moss / Whirlfloc	Last 15 min of boil	Kettle fining; reduces protein carryover
Gelatin	Cold-side (fermenter, keg)	Mix 1 tsp in 100 mL warm water; add to cold-crashed beer; 48–72 h
Isinglass	Cold-side	Attracts yeast cells; effective, fish-derived
Bentonite	Fermenter	Less common in beer than wine/cider; can strip haze-forming proteins but may also reduce some flavor/aroma intensity

Next Batch Prevention

• Add Whirlfloc or Irish Moss at 10–15 min before end of boil.

• Perform a proper whirlpool rest before transferring.

• Cold crash before packaging (Brewfather fermentation step: add a cold crash reading).

---

Playbook 4: Over-Carbonation

Confirm the Problem

• Bottles gushing on opening; foam fills the glass before liquid; high carbonation in packaged product.

⚠️ Safety: Over-carbonated bottles can explode. If you suspect significant over-carbonation, store bottles in a sealed container (cooler, box) in a cool area. Wear eye protection when opening. Check one bottle: if it gushes, do not serve others until diagnosed.

Decision Tree

Were bottles carbonated with priming sugar?
  → YES: Continue...

Was FG confirmed stable with two readings 24–48 h apart before bottling?
  → NO: Fermentation was incomplete; residual sugars + priming sugar = over-carbonation. Danger zone.
  → YES: Continue...

Was priming sugar calculated correctly for the target carbonation level?
  → NO (too much added): Over-carbonation likely. Refrigerate all bottles immediately — cold slows re-fermentation.
  → YES: Continue...

Was equipment sanitary? Could a wild yeast or bacteria have gotten in?
  → Possible: Biological over-attenuation (wild yeast ferments dextrins). Beer likely tastes off.
  → NO: Continue...

Were bottles conditioned warm (>24 °C / 75 °F)?
  → YES: Warmer storage accelerates carbonation and can amplify over-carbonation risk if FG or priming was misjudged.

Immediate Actions (Current Batch)

1. Refrigerate all bottles immediately. Cold significantly reduces further fermentation and CO₂ release.

2. Carefully open one cold bottle as a test. Listen for excessive pressure.

3. If pressure is excessive, carefully vent and re-cap bottles one at a time (with eye/hand protection), then keep cold.

Next Batch Prevention

• Always confirm FG is stable (two readings 24–48 h apart) before bottling.

• Use Brewfather's Carbonation Tool (Tools → Carbonation) to calculate the exact priming sugar weight for your batch volume, desired CO₂ volume, and current beer temperature.

• Measure priming sugar by weight, not volume.

• Consider kegging for precise pressure carbonation control.

---

Playbook 5: Under-Carbonation

Confirm the Problem

• Beer pours flat or with very little head; low CO₂ evident.

Decision Tree

Was the correct amount of priming sugar added (confirmed by weight)?
  → NO: Too little sugar added. Cannot fully correct in-bottle; see below.
  → YES: Continue...

Was conditioning temperature adequate (18–24 °C / 64–75 °F)?
  → NO (too cold): Move bottles to a warmer location for 1–2 weeks.
  → YES: Continue...

Has sufficient conditioning time elapsed (minimum 2 weeks at 20 °C)?
  → NO: Continue conditioning.
  → YES: Continue...

Is yeast in suspension likely too low? (Very clear beer, highly flocculant strain, long cold storage before bottling)
  → YES: For future batches, add a small dose of fresh yeast at bottling.
  → Continue: Priming sugar may have been under-calculated or unevenly mixed.

Immediate Actions (Current Batch)

• Move bottles to 20–22 °C (68–72 °F) and wait 1–2 more weeks before evaluating.

• If still flat after 4 weeks at proper temperature: consider a controlled re-yeast/re-prime procedure bottle-by-bottle with strict sanitation and measured sugar dosing.

Next Batch Prevention

• Use the Brewfather Carbonation Tool — input actual beer temperature at time of bottling, batch volume, and target CO₂ volumes for your style.

• Ensure at least a small amount of active yeast is present at bottling (do not filter before bottling without adding fresh yeast).

---

Playbook 6: Oxidation

Confirm the Problem

• Cardboard, papery, stale, or sherry-like notes developing after packaging or over time.

• Flavors worsen with age (vs. improving or staying stable).

Decision Tree

When did oxidized flavors appear?
  → Immediately after kegging/bottling: O₂ pickup during transfer.
  → Appearing/worsening over weeks: Oxygen ingress via packaging seals or caps.
  → After dry-hopping: Dry-hop addition introduced O₂.

Immediate Actions (Current Batch)

• Oxidation is largely irreversible once present.

• Drink the beer young/fresh rather than aging; oxidized beer does not improve.

• Evaluate whether the flavor is severe enough to affect enjoyment.

Next Batch Prevention

• Closed transfers: Use CO₂ pressure to push beer between vessels rather than gravity/siphon-with-air.

• Purge all vessels with CO₂ before filling.

• Minimize splashing at any point post-fermentation.

• For dry hopping: minimize O₂ exposure when adding hops — pre-purge the hop vessel; use a CO₂-purged container or hop spider.

• Use oxygen-absorbing bottle caps and properly torque crown caps.

---

Playbook 7: Hop Harshness / Harsh Bitterness

Confirm the Problem

• Bitterness is harsh, astringent, lingering, or unpleasant rather than clean and balanced.

• IBU calculation suggests bitterness should be balanced, but taste says otherwise.

Decision Tree

Is there also astringency (dry, puckering, tea-like sensation)?
  → YES: Tannin extraction is contributing — see Playbook 1 (mash/sparge temperature and pH).
  → NO: Continue...

Are hops old or of uncertain freshness?
  → YES: Oxidized alpha acids produce harsher bitterness than fresh iso-alpha acids.
  → Use Brewfather's Hop Freshness tool to estimate HSI (Hop Storage Index) and alpha acid degradation.

Did the beer have minimal or no cold-conditioning?
  → YES: Conditioning softens perceived bitterness; lager especially requires weeks of cold conditioning.
  → NO: Continue...

Is the water sulfate level very high (>200 ppm SO₄)?
  → YES: Sulfate accentuates hop dryness and sharpness; reduce for softer bitterness.
  → NO: Continue...

Is the IBU:OG ratio (BU:GU) very high for the style?
  → YES: Recipe is imbalanced for the style; reduce bittering hop additions or increase OG.
  → NO: Consider that perceived bitterness is influenced by residual sweetness (FG), attenuation, and water chemistry.

Immediate Actions (Current Batch)

• Extended cold conditioning (weeks to months at 0–4 °C / 32–39 °F) will soften bitterness.

• If in fermenter: adding a small amount of gelatin fining can reduce some polyphenol-based harshness.

Next Batch Prevention

• Use fresh hops; store hops vacuum-sealed in a freezer. Use Brewfather's Hop Freshness Tool to estimate alpha acid viability.

• Adjust water chemistry: for soft, round bitterness, reduce sulfate (< 100–150 ppm); for dry, crisp bitterness, use 150–250 ppm SO₄.

• Allow adequate cold conditioning time.

• Cohumulone is only one contributor to bitterness quality; prioritize overall hop freshness, recipe balance, and process control over single-metric hop selection.

---

Playbook 8: Contamination (General)

Confirm the Problem

• Off-flavors: sour, vinegar, musty, medicinal, rope-like, slimy texture.

• Visible signs: floating pellicle (film on surface), visible mold, unusual turbidity with off-aroma.

Decision Tree

Is there a visible pellicle (ropey, white/tan film on beer surface)?
  → YES: Wild yeast (Brettanomyces) or Lactobacillus/Pediococcus contamination.

Is the flavor sour/acidic?
  → Lactic + vinous: Lactobacillus or Pediococcus.
  → Acetic/vinegar: Acetobacter (requires oxygen; check for O₂ exposure during fermentation).

Is the flavor medicinal/band-aid?
  → Chlorophenols (chlorinated water + phenolics) or wild yeast. Check water treatment.

Is there visible mold (colored growth — green, black, pink)?
  → Mold contamination. Discard the batch. Do not consume.

Immediate Actions (Current Batch)

• Mold visible: Discard the batch — molds can produce mycotoxins.

• Bacterial/wild yeast contamination: Evaluate flavor. Mild lactic sourness may be palatable; acetic/vinegar usually is not. If flavor is objectionable, discard.

• Identify and remove contamination vector before next batch.

Contamination Sources

• Scratched plastic equipment (replace any scratched fermenters, tubing, or autosiphons)

• Inadequate sanitizer contact time or concentration

• Residual organic matter (incomplete cleaning before sanitizing)

• Airborne contamination (open fermenters near composting material, fruit, etc.)

• Untreated chlorinated/chloraminated water (chlorophenol risk)

Next Batch Prevention

• See Cleaning, Sanitation & Safety for full process.

• Audit all plastic equipment for scratches; replace suspect items.

• Confirm sanitizer concentration and contact time.

• Treat water with Campden/metabisulfite at an appropriate dose to remove chlorine/chloramine before brewing.

---

Quick-Reference Diagnostic Cheat Sheet

Symptom	Most Likely Cause	Quick Check
Low OG	Efficiency loss	Check crush, mash conversion, volume
Gravity not dropping	Stalled fermentation	Check temp, rouse yeast
Butter/butterscotch	Diacetyl	Raise temp, diacetyl rest
Green apple	Acetaldehyde	More conditioning time
Cooked corn	DMS	Boil uncovered, faster chill
Solventy/hot	Fusel alcohols	Lower fermentation temp
Band-aid/medicinal	Chlorophenol / wild yeast	Treat water; check sanitation
Cardboard/papery	Oxidation	Closed transfers, CO₂ purge
Sour/acidic	Bacterial contamination	Audit sanitation and equipment
Gushing bottles	Over-carbonation	Check FG stability, priming calc
Flat beer	Under-carbonation	Check priming calc, temp, time
Persistent haze	Protein / yeast	Cold crash, finings, Irish moss
Harsh bitterness	Old hops, tannins, water	Hop freshness, water chemistry

---

Sources

• Palmer, J.J. (2017). How to Brew: Everything You Need to Know to Brew Great Beer Every Time (4th ed.). Brewers Publications.

• White, C. & Zainasheff, J. (2010). Yeast: The Practical Guide to Beer Fermentation. Brewers Publications.

• Fix, G. (1999). Principles of Brewing Science (2nd ed.). Brewers Publications.

• Bamforth, C.W. (2003). Beer: Tap into the Art and Science of Brewing. Oxford University Press.

• Briggs, D.E. et al. (2004). Brewing: Science and Practice. Woodhead Publishing.

• Daniels, R. (1996). Designing Great Beers. Brewers Publications.

• American Homebrewers Association (AHA): troubleshooting and sanitation guidance.

• Brewers Association: Draught Beer Quality Manual (packaging, oxidation, and dispense-related quality risks).