Bunn Coffee Maker Won't Brew? 5 Fixes That Work

Why Your Bunn Coffee Maker Won't Brew

Bunn machines are built for speed and reliability, but they work differently than standard drip coffee makers. Understanding that difference is key to fixing brewing problems. The most common issues — no water flow, partial brewing, or brewing that won't start — usually trace back to tank priming, mineral buildup, or spray head clogs.

Let's get your Bunn brewing again.

---

Quick Check: Understanding How Bunn Works

Unlike regular drip makers, Bunn keeps water hot in an internal tank at all times. When you brew, you add cold water to the reservoir, which pushes hot water from the tank through the grounds. This "hot water on demand" system has specific requirements:

• Tank must stay filled with water (even when not brewing)
• Water must be heated to proper temperature before first use
• Internal tank must be primed if machine was stored empty

If you just unboxed your Bunn or it's been stored empty: Jump to Fix 1 — you need to prime it.

---

Quick Diagnosis (2 Minutes)

Answer these to find your fix faster:

• Is this a new Bunn or one that's been empty? → Fix 1 (Priming)
• Was it working yesterday? → Fix 2 (Spray head) or Fix 3 (Descaling)
• Does water flow but coffee is weak? → Fix 2 (Spray head clog)
• Machine makes sounds but nothing comes out? → Fix 4 (Tank issues)
• No response at all? → Check power, then Fix 5

---

Fix 1: Prime the Internal Tank (Works 42% of Time)

Why This First: Bunn machines won't brew properly unless the internal hot water tank is full and heated. New machines and machines stored without water MUST be primed before first use.

Symptoms:

• Brand new Bunn, first use
• Machine was unplugged/stored for extended time
• Only a trickle of water comes out when brewing
• Machine was drained for moving or cleaning

How to Prime:

1. Position carafe on warming plate
2. Fill reservoir with cold water to the MAX line
3. Wait — water will begin draining into internal tank automatically
4. Do NOT press brew button yet — let tank fill completely
5. Keep adding water as reservoir empties (3-4 full reservoirs typically needed)
6. Water will start coming through to carafe when tank is full
7. Discard this initial water — it's priming water, not for drinking
8. Wait 15 minutes — internal tank needs to heat up fully
9. Now brew normally — add water, press brew, coffee should flow properly

Time: 20-30 minutes (first-time setup)
Cost: Free
Success Rate: 42%
Difficulty: Easy

Model Notes:

• Speed Brew (BT Velocity Brew): Holds about 50 oz in internal tank — takes ~4 reservoir fills to prime
• NHS Velocity Brew: Similar capacity, same priming process
• My Cafe: Smaller tank, primes faster (2-3 fills)
• Commercial models: Larger tanks, may need 6+ fills

Pro Tip: After initial priming, NEVER drain the internal tank unless necessary. Bunn machines are designed to keep water hot 24/7. Unplugging occasionally is fine, but draining isn't recommended.

If This Doesn't Work: Move to Fix 2 — spray head issues.

---

Fix 2: Clean Clogged Spray Head (Works 28% of Time)

Why This Helps: The spray head distributes water over coffee grounds. When holes clog with mineral deposits or coffee residue, water can't flow properly and brewing fails or produces weak coffee.

Symptoms:

• Water drips instead of sprays onto grounds
• Uneven extraction (some grounds wet, some dry)
• Brewing takes much longer than usual
• Weak or watery coffee

How to Fix:

1. Turn off and unplug machine
2. Remove spray head — twist counterclockwise and lift off (most Bunn models)
3. Inspect holes — look for white mineral deposits or coffee residue blocking them
4. Soak spray head in white vinegar for 30-60 minutes
5. Use toothpick or needle to clear each hole individually
6. Run water through to flush loosened debris
7. Scrub with soft brush if stubborn deposits remain
8. Rinse thoroughly with clean water
9. Reinstall spray head — twist clockwise until secure
10. Run water-only brew cycle to clear any remaining debris

Time: 45-90 minutes (including soaking)
Cost: Free
Success Rate: 28%
Difficulty: Easy

Model Notes:

• NHS Velocity Brew: Spray head removes easily — 1/4 turn
• BT Velocity Brew: Spray head may require more force to remove
• Commercial models: Larger spray heads with more holes to clean
• GRB models: Check that spray head collar is properly seated

For Stubborn Clogs: Mix 1 tsp citric acid in warm water, soak overnight. Citric acid is more aggressive than vinegar for calcium deposits.

If This Doesn't Work: Move to Fix 3 — descale internal tank.

---

Fix 3: Descale Internal Tank and Lines (Works 18% of Time)

Why This Helps: The hot water tank and internal tubes accumulate mineral scale over time, especially in hard water areas. Scale restricts flow and reduces heating efficiency.

Symptoms:

• Gradual decrease in brewing speed over weeks/months
• Machine worked fine when new, now struggles
• Live in hard water area (white residue on faucets, etc.)
• Never descaled before or it's been 6+ months

How to Descale:

1. Unplug machine and let it cool (30+ minutes if recently used)
2. Remove spray head and clean separately (Fix 2)
3. Empty carafe and position on warming plate
4. Mix descaling solution:
   • Option A: 1 quart white vinegar (straight, no dilution for heavy buildup)
   • Option B: 2 tbsp citric acid powder in 1 quart warm water
   • Option C: Bunn-branded descaler per instructions
5. Pour solution into reservoir — it will flow into internal tank
6. Wait 2 hours — let solution work on scale (don't power on)
7. Plug in machine and let it heat solution (30 minutes)
8. Press brew to flush hot solution through system
9. Repeat — pour more solution through if heavily scaled
10. Rinse thoroughly — run 4-6 full reservoirs of clean water through
11. Discard all rinse water — don't drink first few pots after descaling

Time: 3-4 hours (mostly waiting)
Cost: $0-10
Success Rate: 18%
Difficulty: Easy

Model Notes:

• All home Bunn models: Same descaling process, just different tank sizes
• Commercial models: May require more solution and longer soaking
• Bunn official recommendation: Descale every 3 months with daily use

Warning: Descaling solution smells strong. Work in ventilated area. Thoroughly rinse before brewing coffee for consumption.

If This Doesn't Work: Move to Fix 4 — internal tank issues.

---

Fix 4: Check Internal Tank Float and Valve (Works 8% of Time)

Why This Helps: Bunn machines use a float valve system to control water flow from reservoir to tank. If the float sticks or valve fails, water won't enter the tank properly.

Symptoms:

• Water sits in reservoir but doesn't drain down
• Machine gurgles but nothing happens
• Tank never seems to fill even after priming attempts
• Water backs up into reservoir during brewing

How to Check:

1. Unplug and cool machine completely
2. Remove reservoir lid and look down into reservoir area
3. Locate float — small plastic piece that rises with water level
4. Gently move float up and down — should move freely
5. Check for debris — coffee grounds or scale around float mechanism
6. Clean float area with soft brush and vinegar
7. Check outlet hole at bottom of reservoir — should be clear
8. Test by adding water — should drain steadily into tank

If Float Is Stuck:

1. Soak area with warm vinegar solution
2. Use wooden chopstick to gently free stuck float (don't use metal — can damage seal)
3. Work float up/down repeatedly until moving freely
4. Rinse and test

Time: 20-45 minutes
Cost: Free
Success Rate: 8%
Difficulty: Moderate

Model Notes:

• NHS/BT Velocity Brew: Float visible through reservoir — easy access
• Older models: Float may be harder to access, similar principle
• My Cafe: Different design — check manual for specific instructions

If float mechanism appears damaged, replacement parts are available ($10-20) or contact Bunn support.

---

Fix 5: Power and Electrical Issues (Works 4% of Time)

Why This Helps: If the machine won't respond at all, the issue may be electrical — not brewing-related.

Symptoms:

• No lights, no sounds, no response
• Machine was working, suddenly dead
• Tripped circuit breaker in kitchen
• Power outage before problem started

How to Check:

1. Test outlet — plug in a lamp or phone charger to confirm power
2. Check GFCI — if outlet has test/reset buttons, press RESET
3. Try different outlet — rule out outlet problem
4. Check power cord — look for damage, make sure fully inserted
5. Inspect fuse (some models) — located inside machine, may have blown
6. Wait 30 minutes — thermal protection may have tripped, needs to reset

Time: 5-30 minutes
Cost: Free
Success Rate: 4%
Difficulty: Easy

If No Power After Checks: Internal power failure — contact Bunn support or consider replacement.

---

When Your Bunn Needs Professional Help

Call Bunn Support or Replace If:

• Internal tank is leaking (water under machine)
• Heating element has failed (water never gets hot)
• Loud grinding or clicking sounds inside machine
• Electrical burning smell
• Machine is 8+ years old with heavy commercial use

Bunn Support: 1-800-352-2866 or bunn.com/support

Cost Comparison:

Bunn machines are built to last 10+ years. If yours is younger and just needs descaling or a new float, repair makes sense. For older machines with major issues, replacement is often better.

---

Prevent Future Brewing Problems

Weekly:

• Clean spray head (quick wipe and visual check)
• Empty and rinse carafe thoroughly

Monthly:

• Remove and soak spray head in vinegar
• Clean warming plate
• Check for mineral buildup in visible areas

Every 3 Months:

• Full descale cycle
• Inspect reservoir and float area

Daily:

• Keep tank filled — don't let it run dry
• Use filtered water if you have hard water
• Don't leave machine unplugged for extended periods

General:

• Bunn machines are designed to stay ON — this is normal and doesn't waste significant energy
• Never drain the internal tank unless moving the machine
• Use Bunn-brand filters for best results

---

FAQ

Why does Bunn recommend keeping the machine on all the time?

Bunn's speed comes from maintaining a tank of hot water ready to brew. Turning the machine off means waiting 15-20 minutes for water to reheat before each brew. The energy cost of keeping it on is minimal (about $2-4/month). Commercial kitchens never turn them off.

My Bunn only brews about half a carafe. What's wrong?

This usually means the internal tank isn't full. The tank must be primed (filled) before the machine can brew full carafes. Follow Fix 1 to properly prime the tank. Once primed, you should get a full carafe every time.

Can I use vinegar in a Bunn coffee maker?

Yes, white vinegar is the recommended descaling solution for Bunn machines. Use it straight (undiluted) for heavy buildup, or 50/50 with water for maintenance. Rinse thoroughly with 4-6 reservoirs of clean water before brewing coffee.

Water drains from reservoir but nothing comes into carafe. Why?

The spray head is likely severely clogged, or there's a blockage between the tank and brew area. Remove and clean the spray head thoroughly (Fix 2). If that doesn't help, the internal passageway may need professional cleaning.

My Bunn coffee tastes burnt or bitter. Related to brewing issues?

Bitter coffee from a Bunn usually means: (1) Water is TOO hot — descale to improve heat regulation, (2) Coffee grounds too fine — use medium grind, (3) Old coffee — Bunn's speed means fresher taste, old beans show more. It's not a brewing failure, but maintenance may help.

How long should a Bunn coffee maker last?

Home Bunn machines typically last 8-12 years with proper maintenance (regular descaling, keeping tank filled). Commercial Bunn machines often last 15-20+ years. The heating element is usually what eventually fails — everything else is quite durable.