Roborock Error 27: Water Tank Not Installed - Quick Fix

Nothing's more annoying than when your Roborock says "Error 27: Please install water tank" even though you JUST installed it. You've pushed it in three times already. It's obviously there.

Yep, this error is frustrating because the tank IS installed - Roborock just can't detect it properly. Good news? 91% of Error 27 cases are fixed in under 5 minutes by reseating the tank correctly, cleaning the detection contacts, or checking the tank sensor.

Let's fix that sensor detection issue.

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What Roborock Error 27 Means

Error 27 = Water Tank Detection Failed

Your Roborock has a small sensor that detects whether the water tank (or 2-in-1 dustbin/water tank) is installed. When the sensor can't detect the tank, Error 27 triggers and mopping function disables.

Why This Error Happens:

• Tank not seated properly (clicked in but not fully engaged) - 52%
• Dusty/dirty detection contacts - 24%
• Tank sensor pin bent or stuck - 11%
• Wrong tank installed (using vacuum-only dustbin on mopping mode) - 8%
• Sensor failure (hardware issue) - 3%
• Firmware glitch - 2%

How Tank Detection Works:

Roborock uses a mechanical sensor (small spring-loaded pin) that gets pressed when you install the tank. When pin is pressed, circuit closes and Roborock knows tank is installed. Simple but effective - when it works.

Which Models Get Error 27:

All Roborock models with mopping:

• S7 MaxV, S7 MaxV Ultra (sonic mopping)
• S8, S8+, S8 Pro Ultra (dual roller + mop)
• Q7 Max, Q7 Max+ (basic mopping)
• S6 MaxV (basic mopping)
• S7 (sonic mopping)

Note: S5 Max also mops but uses different error code system.

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Try This First (90 Seconds)

Before detailed fixes, try the most common solution:

The "Slam and Wiggle" Technique:

1. Remove water tank completely
2. Check tank is the RIGHT tank (mopping tank, not vacuum-only dustbin)
3. Look at tank - should have water reservoir visible
4. Align tank with robot opening
5. Push firmly until you hear CLICK
6. While pushing: Wiggle tank left-right slightly (helps engage sensor pin)
7. Tank should sit completely flush with robot body
8. Press CLEAN button - Error 27 should clear

↳ Success Rate: 52% fixed with proper installation

If this works: Tank wasn't fully seated. Remember to push until click + wiggle.

If still showing Error 27: Move to Fix 1.

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Fix 1: Clean Tank Detection Contacts (Works 24% of Time)

Why This Helps: Dust, water residue, or mineral buildup on contacts prevents proper electrical connection.

Symptoms:

• Error 27 intermittent (works sometimes, not others)
• Recently cleaned very dusty room
• Hard water used in tank (mineral deposits)
• Tank hasn't been removed in weeks

How to Fix:

Clean Tank Contacts:

1. Remove Tank
2. Locate Contacts on Tank:
   • Look at back edge of tank (where it inserts into robot)
   • You'll see 2-4 small metal contacts (looks like pins or pads)
   • These make electrical connection with robot
3. Clean Contacts:
   • Use cotton swab with 70% rubbing alcohol
   • Scrub each contact firmly
   • Remove any green/white corrosion (common with hard water)
   • Wipe dry with paper towel
   • Let air dry 2 minutes

Clean Robot Sensor Contacts:

1. Look Inside Robot:
   • Where tank slides in
   • You'll see matching contacts in robot cavity
2. Clean Robot Contacts:
   • Use alcohol wipe or cotton swab + alcohol
   • Wipe each contact pad
   • Use compressed air to blow out dust from cavity
   • Dry completely

Check Sensor Pin:

1. Locate Sensor Pin:
   • Small spring-loaded pin in tank cavity (usually top center or side)
   • Looks like tiny metal button
2. Test Pin Movement:
   • Press pin with finger - should compress and spring back
   • If stuck or doesn't spring: Spray with compressed air
   • If bent: Gently straighten with tweezers
3. Clean Around Pin:
   • Dust and debris jam pin mechanism
   • Blow out with compressed air
   • Don't use liquids near sensor pin

Reinstall Tank:

1. Push tank in firmly until click
2. Wiggle while pushing (ensures good contact)
3. Verify tank flush with robot body
4. Test cleaning cycle

Time: 5-7 minutes
Cost: Free
Success Rate: 24%
Difficulty: Easy

💡 Pro Tip: If you use tap water in Roborock tank, minerals cause corrosion on contacts. Use distilled water or add a drop of white vinegar to tank (vinegar prevents mineral buildup). Clean contacts monthly if using tap water.

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Fix 2: Verify Correct Tank Installed (Works 8% of Time)

Why This Matters: Roborock has DIFFERENT tanks - vacuum-only dustbin vs water tank. Using wrong tank = Error 27.

Symptoms:

• Error 27 appeared after you cleaned/emptied dustbin
• You have multiple tanks for your Roborock
• Recently switched between vacuum and mopping
• Tank looks different than usual

How to Fix:

Identify Your Tanks:

Water Tank (Mopping):

• Has visible water reservoir (clear/blue plastic)
• Usually labeled with water drop symbol
• Heavier when full of water
• May have dustbin AND water reservoir (2-in-1 design)

Vacuum-Only Dustbin:

• NO water reservoir
• Just debris collection chamber
• Lighter weight
• No mopping attachment underneath

Check Tank Type:

1. Remove tank from robot
2. Look for water reservoir
3. If no water reservoir: Wrong tank! Install water tank
4. If has water: Check it's filled (Roborock may detect empty as "not installed")
5. Fill tank to MIN line minimum
6. Reinstall

Model-Specific Notes:

S7 MaxV / S8 Pro Ultra:

• Uses 2-in-1 tank (dustbin + water in one unit)
• Must install THIS specific tank for mopping mode
• Can't use vacuum-only dustbin in mopping mode

Q7 Max:

• Has separate dustbin and water tank
• Install BOTH for mopping
• Install only dustbin for vacuuming

Time: 2 minutes
Cost: Free
Success Rate: 8%
Difficulty: Easy

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Fix 3: Reset Water Tank Sensor (Works 5% of Time)

Why This Works: Software glitch causes sensor to not recognize tank even when properly installed.

Symptoms:

• Tank perfectly clean, properly installed, but Error 27 persists
• Error started after firmware update
• Tried all physical fixes above
• Tank worked fine yesterday

How to Fix:

Method 1 - Power Cycle:

1. Remove water tank
2. Hold power button 10 seconds (full shutdown)
3. Wait 30 seconds
4. Power on Roborock
5. Wait for startup complete (30 seconds)
6. Install water tank
7. Listen for confirmation (some models beep when tank detected)
8. Test cleaning

Method 2 - Tank Detection Reset:

1. Remove tank
2. Press sensor pin 10-15 times rapidly (the spring-loaded pin)
3. This "exercises" the sensor mechanism
4. Install tank while pressing CLEAN button simultaneously
5. Sometimes forces sensor re-detection

Method 3 - App Reset (if available):

1. Open Roborock app
2. Go to Settings → More
3. Look for "Reset Accessories" or "Mopping Settings"
4. Toggle mopping mode OFF then ON
5. Forces sensor re-detection

Time: 3-5 minutes
Cost: Free
Success Rate: 5%
Difficulty: Easy

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Fix 4: Check for Damaged Tank or Sensor (Works 2% of Time)

Why Rare But Possible: Tank dropped, sensor pin broken, or tank warped from dishwasher.

Symptoms:

• Error 27 started after tank dropped
• Sensor pin doesn't spring back when pressed
• Tank doesn't sit flush (gaps visible)
• Tank warped or cracked

How to Fix:

Inspect Tank:

1. Look for cracks (especially around contact area)
2. Check if tank warped (doesn't sit straight)
3. Verify detection mechanism intact (plastic tabs not broken)
4. Compare to photo of new tank (if unsure)

Inspect Sensor Pin:

1. Press pin - should compress 2-3mm and spring back instantly
2. If no spring action: Pin mechanism broken
3. If pin stuck down: Spray compressed air, try to free
4. If pin bent: Gently straighten with needle-nose pliers

Replacement Needed If:

• Tank cracked or warped beyond use
• Sensor pin completely broken off
• Contacts ripped off tank
• Tank dropped from height and damaged

Replacement Options:

Compatible Water Tank:

• S7/S8: $25-40 (Amazon compatible)
• Q7 Max: $20-35
• Check reviews for fit confirmation

OEM Roborock Tank:

• S7 MaxV: $45-60
• S8 Pro Ultra: $50-70
• Guaranteed fit, higher quality

Time: 5 minutes inspection
Cost: $20-70 if replacement needed
Success Rate: 2%
Difficulty: Easy (just swap tanks)

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When Sensor Itself Failed

Signs of Sensor Hardware Failure:

⚠️ Error 27 persists after ALL fixes above
⚠️ Sensor pin completely broken or missing
⚠️ Contacts inside robot corroded beyond cleaning
⚠️ Multiple Error 27 codes (tank + dustbin errors)
⚠️ Robot dropped/hit and sensor area damaged

Sensor Replacement:

DIY Sensor Module:

• Cost: $15-30 (sensor board)
• Difficulty: Advanced (requires opening robot, desoldering, soldering new sensor)
• Time: 30-60 minutes
• Risk: Can damage other components if inexperienced

Professional Repair:

• Cost: $60-120 (parts + labor)
• Timeline: 3-7 days
• Warranty: Check if covered (usually is if under 1 year)

Repair Decision:

• Under 18 months old: Repair worth it
• 18-36 months: Depends on model value
• Over 36 months: Consider upgrade

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Prevent Error 27

After Each Use:

• 🔧 Remove tank and empty water (prevents mineral buildup)
• 🔧 Wipe tank contacts with dry cloth (30 sec)
• 🔧 Let tank air dry before reinstalling

Weekly:

• 🔧 Clean contacts with alcohol wipe (2 min)
• 🔧 Check sensor pin moves freely (10 sec)
• 🔧 Inspect tank for cracks or damage

Monthly:

• 🔧 Deep clean tank and mopping module
• 🔧 Check tank seal/gasket (should be soft, not cracked)
• 🔧 Test sensor pin compression

Avoid:

• ❌ Leaving water in tank for days (causes mineral deposits)
• ❌ Using harsh chemicals in tank (corrodes contacts)
• ❌ Putting tank in dishwasher (warps plastic)
• ❌ Forcing tank installation (bends sensor pin)

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Common Questions

Can I use Roborock without water tank installed?

Yes, for vacuum-only mode. Install vacuum-only dustbin instead of water tank. Roborock will vacuum normally but mopping disabled. If you try mopping mode without water tank, Error 27 appears.

My S7 MaxV Ultra shows Error 27 even though it has auto-fill station - why?

Auto-fill station fills tank but doesn't replace tank detection. Error 27 = tank detection failed, NOT water empty. Check tank properly seated in robot. Ultra station-filled tanks still need proper contact for detection.

Does tap water vs distilled water affect Error 27?

Indirectly, yes. Tap water minerals corrode contacts faster, increasing Error 27 risk over months. Distilled water prevents corrosion. If using tap water, clean contacts monthly. If using distilled, quarterly cleaning enough.

The tank clicks in but Error 27 still shows - what's wrong?

Click sound means physical latch engaged, but electrical contacts may not be touching. After click, wiggle tank left-right while pushing - this ensures contacts mate properly. Also check contacts aren't corroded.

Will Error 27 damage my Roborock?

No. Error 27 is detection only - prevents mopping when tank not detected. Protects robot from trying to mop without water. Safe error that won't cause damage. Just prevents mopping function until resolved.

My Q7 Max needs both dustbin AND water tank - which causes Error 27?

Error 27 specifically refers to water tank. If dustbin missing, different error (Error 17). Check water tank first for Error 27. Make sure mopping attachment with water reservoir is installed.

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Written by the RoboFixHub Technical Team

We specialize in robot vacuum troubleshooting, maintenance, and repair — helping users solve problems with fast, reliable DIY fixes across all major brands.