“Transparency: As an Amazon Associate, we earn from purchasing. The number one complaint about campervan toilets: smell. Here is how to eliminate odours with proper venting.
Verdict
A £15 powered vent (computer fan + switch + hole) eliminates 95% of campervan toilet odours. Installing one takes 30 minutes and a drill. It is the best upgrade you can make to your van's toilet.
Why Cassette Toilets Smell
The waste tank is sealed but not airtight. When the internal pressure builds (from waste gases), air escapes through the flush seal. That is the smell you notice. A vent eliminates the pressure by letting air escape to the outside.
The Basic Vent
A 20mm hole in the van floor under the toilet, covered by a small ventilation grille (£3, Screwfix). The natural pressure difference between the waste tank and the outside air pushes odours down and out. No fan, no moving parts. Installation: Drill a 20mm hole through the van floor directly under the toilet cassette. Fit a small mesh grille on the inside (stops insects). The hole creates a passive airflow path from the cassette to the outside. Does it work? Partially. It reduces smell by 60-70%. The pressure still builds faster than the passive vent can release it.
The Powered Vent
A 12v computer fan (80mm, £8 from Amazon) mounted in the floor vent, wired to a switch. The fan runs continuously or on a timer, actively extracting air from the toilet compartment. Installation:
- Cut a 80mm hole in the floor near the toilet
- Mount the fan so it blows downward (extracting air from inside)
- Wire to a 12v switch (or to the same switch as the toilet light)
- Add a small grille on the inside (mesh to stop debris)
- The fan runs at 5-8W, nearly silent Result: 95% odour reduction. The fan creates negative pressure in the toilet compartment, so air flows from the van into the toilet, not the other way.
The "Vent Under the Seat" Hack
If you have a Thetford cassette toilet in a bench seat, the easiest venting hack:
- Remove the bench seat base panel
- Cut a 50mm hole in the side panel (hidden from view)
- Fit a small 12v fan in the hole, wired to a toggle switch
- The fan pulls air from inside the seat (where the cassette lives) and vents it into the van's main space
- Open a roof vent to complete the airflow This works because the toilet cassette is in a sealed compartment. The fan prevents odour from escaping into the living space.
Activated Carbon Filter
A passive option: fit an activated carbon filter (£10, aquarium filter) in the cassette's vent pipe. The carbon absorbs odour molecules. Replace every 3-6 months. It is not as effective as a powered vent but requires no wiring.
The Best Solution
Combination: Passive floor vent + computer fan + switch. The fan runs when the toilet is in use and for 10 minutes after. The passive vent handles the rest. Total cost: £15. Installation time: 30 minutes.
Odour Prevention (Beyond Venting)
- Use green (enzyme-based) toilet fluid, not blue (formaldehyde). The green stuff actually breaks down waste.
- Empty the cassette every 2-3 days (not 4-5). Fresher waste smells less.
- Rinse the cassette with fresh water after emptying (removes residue).
- A squirt of white vinegar in the flush tank after emptying — neutralises ammonia.
- Keep the toilet seat closed when not in use.
