Most Mars caravans are fitted with a Dometic cassette toilet (commonly the CTS 4110). The toilet sits inside the bathroom; the waste cassette slides out from an external service door so you can roll it to a dump point. This is the full reference — use it the first time, then keep the quick-reference Cassette Toilet Quickie bookmarked for trips.

Quick Highlights

• Cassette capacity: 19L
• Power: 12V DC (flush and control panel)
• Bowl: scratch-resistant ceramic inlay
• Cassette access: external service door on the side of the van
• Minimum water pump output for flushing: 7 L/min
• Max user weight: 130 kg

Know the Main Parts

• Flush button and level indicator panel (inside the bathroom)
• Blade/slider handle — opens and closes the drop into the cassette
• External service door — where you remove the cassette
• Cassette pour spout and cap
• Vent button — lets air in so the cassette drains smoothly
• Pull-out handle and wheels — roll the cassette to the dump point

What You'll Need

• Disposable gloves and hand sanitiser
• Approved dump point access
• Fresh water for rinsing
• Approved sanitary additive for cassette toilets
• Mild, non-abrasive cleaner and a soft cloth
• Silicone-based grease or spray for seal maintenance

Before First Use (1-Minute Setup)

1. Open the external service door.
2. Push the cassette lock upwards to release.
3. Pull the cassette out to the stop, then lift it fully out.
4. Stand it upright, rotate the pour spout up about 90°, remove the cap, and add an approved tank treatment via the spout (follow product dosing).
5. Refit the cap and return the spout to the stored position. Do not rotate the spout more than 90° — on some models it can come off.
6. Slide the cassette back in until it stops. The lock should close automatically — always confirm it's firmly seated.
7. Close and lock the service door.

Everyday Use

1. Open the blade: pull the blade handle forwards.
2. Pre-wet the bowl: briefly press the flush button to put a little water in.
3. Use the toilet: leave the blade open during use.
4. Flush: press the flush button to rinse.
5. Close the blade: push the handle back to close.

Travel rule: the blade must be closed while towing, and no liquid should sit above the closed blade.

Tip: If you can, use fast-dissolving RV toilet paper — household paper raises the risk of clogging and false "full" readings.

Control Panel Icons

• Flush button — activates the flush
• Cassette removed — cassette isn't seated correctly
• Fill fresh water tank — flush water supply is low (not all installs use this)
• Cassette 3/4 full — plan to empty soon
• Cassette full — empty immediately

When & How to Empty the Cassette

Empty when the "nearly full" indicator lights — that usually triggers around 80% capacity, leaving you only a couple of uses.

Important: on slopes or long inclines, never let the cassette go above 3/4 full — overflow through the vent is possible.

Step-by-Step Emptying (No-Splash Method)

1. Confirm the blade inside is closed.
2. Open the external service door.
3. Unlock the cassette and pull it out using the handle and wheels.
4. Roll it to an authorised dump point.
5. Stand it upright, rotate the spout up about 90°, and remove the cap.
6. Point the spout down into the dump point.
7. Now press the vent button — only once the spout is pointing down. This lets air in for smooth, splash-free draining.
8. Rinse the cassette thoroughly with clean water.
9. Add your sanitary additive per product instructions.
10. Refit the cap, return the spout to stored position, and slide the cassette back in until fully seated.
11. Close and lock the service door.

Dump Point Etiquette

• Use designated dump points only — follow site signage.
• Rinse any splashes and leave the area clean for the next person.
• Never empty waste anywhere it isn't permitted. It's unhygienic and can damage local systems.

Cleaning & Regular Care

Bowl & Exterior

• Use a soft cloth, lukewarm water and a mild, colourless detergent.
• Rinse with clean water.
• Avoid cleaners containing chlorine, alcohol, abrasives, or polish — they can damage components and seals.

Cassette Tank

• Always rinse thoroughly after emptying.
• Never use a high-pressure cleaner inside the cassette — it can damage the float and level indicator.
• Don't shake the cassette vigorously.

Seals & Blade (Stops Smells, Keeps the Slide Smooth)

• Clean the toilet and cassette seals regularly — monthly if you're using the van often.
• Lubricate the main blade seal once or twice a year with silicone-based grease or spray (Dometic manuals reference products like OKS® 1110 grease and OKS® 1111 silicone spray).
• Pinch hazard around the blade mechanism — be careful when cleaning or greasing.

Winter Use & Long-Term Storage

• You can keep using the toilet in winter if the toilet and cassette are kept in a frost-protected location.
• If frost is possible, empty the fresh water tank, the cassette tank, and the fresh water supply pipes.
• Never use antifreeze in the sanitation system — it can damage seals and components.
• For long storage: flush until there's no water left in the pipes, empty and rinse the cassette, and let it dry with the spout cap off.

Quick Troubleshooting

• Flush no longer works: blown fuse. Replace the control panel fuse (7.5A automotive). If it blows again, check terminals and wiring.
• Cassette leaking: worn blade seal. Replace it and ensure it seats evenly.
• No fill level display: float is jammed (often by toilet paper). Clean the float — do not use high-pressure cleaning.
• Bad smells: empty more often, dose the additive correctly, rinse the cassette well after every drain.
• Sticky slider: clean and lubricate the seal with silicone-based product.
• Splashing when emptying: the spout must be pointing fully down before you press the vent button.
• False "full" reading: thorough rinse can help; persistent false reads usually mean the float needs cleaning.

Helpful Habits

• Pre-wet the bowl before use and always flush after.
• Empty a little early — don't run it constantly at "full".
• Keep seals clean and lightly lubricated (silicone-based only).
• Use dump points and follow local rules.

Buttons, indicators and cassette shape vary slightly between Dometic models fitted to Mars vans, but the principles above apply across the range.