The cassette toilet – a guide to the ins and outs

New caravanners or RVers often come away from their first encounter with a cassette toilet with more questions than answers. What are they, how do they work, and do they smell?

A cassette toilet is a low maintenance toilet where the waste is stored in a small removable sealed container (called the cassette), which can be taken out of the van and wheeled to a dumping station or local toilet to be emptied. This toilet uses two chemicals to neutralise odours and stay clean.

General overview

Cassette toilets are manufactured by a number of companies but the manufacturers most known for them are Thetford, Dometic and Camec. They vary in size, shape and function but operate on the same basic principle where by waste is stored in a removeable container called a cassette that can be emptied when required. The cassettes are usually 15 to 20 litres in capacity which is enough for three to five days of use. This is obviously dependent on the amount of use.

The waste in the tank is treated with an odour neutralising agent that also assists to break down solids to allow easier emptying.  This chemical comes in two forms and can be septic safe meaning that the waste can be emptied in to any toilet system if needed.

The flush tank can have a second chemical added which further neutralises odours and helps keep the toilet bowl clean. This chemical is also septic tank safe.

The cassette itself is usually manufactured to resemble a small suit case on wheels. This can be removed from the caravan or RV via a hatch on the outside and wheeled to the dumping station. Emptying the cassette is relatively easy via an easy pour tube at the top of the cassette. A press button vent can be pressed during emptying to prevent air locks and unwanted “gurgling” while emptying.

How do you use it?

The cassette toilet is almost like using a regular toilet with the only difference being that there is an additional lever to be turned prior to using the toilet. This opens the trap door between the waste holding tank and the toilet bowl. You then use the toilet normally (though try not to use too much toilet paper) and use the flush button afterwards. The flush simply runs the rinsing solution over the toilet bowl to leave it clean and fresh.

If you find that you have left some undersirable “skid marks”, use a spray bottle on stream to shoot off the remnants. To prevent this happening in the first place, it can help to do a quick pre-flush before sitting down to lubricate the surface of the bowl and reduce the likelihood of skid marks.

Finish the process by closing the lever again to close off the waste holding tank.

Voila, cassette toilet successfully used!

How long does it last?

This all depends on how many people using it and their requirements. For the two of us it normally lasts between three and five days. This can be extended by using the flush button sparingly. One trick to help with this is to use a spray bottle of the rinse solution to spray the bowl after use instead. This reduces the amount of rinse solution that enters the waste holding tank but still leaves your toilet fresh and clean.

The cassette full light will illuminate when the cassette ios near to its absolute capacity and you should try to empty it as soon as possible. If you find that the cassette fills at the worst possible time, one option is to purchase a second cassette. These are about $200 and will allow you to go for much longer in between emptying.

Does it smell?

This all depends on how you clean and prepare the waste holding tank. If you follow the manufacturers recommendations and use the recommended chemicals, these toilets do not smell. Most of the time when people say their toilet smells in between uses, its usually comes down to one of three things:

• Incorrect chemical or amount of chemical added to the holding tank
• Cassette seals are old or damaged
• The toilet has been used while the cassette is removed.

Adding the right amount of chemical to the holding tank is essential to breakdown waste and ensure that odours are minimised. Using either the wrong chemical or too little chemical will not allow the intended chemical reaction to occur in the waste holding tank and it will likely not eliminate the odours. Always use the recommended chemicals for your particular toilet or at least one that works on the same active ingredient and always check that the dosage is correct. Cheaper alternatives can be problematic and may not work as well as the chemicals designed for the system.

In other cases, odours from the holding tank may be leaking out of old or damaged seals between the cassette and the toilet bowl. These seals are made from rubber or silicone and can become hard with age. The harder these seals become, the more prone to cracking or poor sealing they are. This can allow the odours from the waste holding tank to escape. A visual check while emptying the cassette will give you a pretty good idea of their condition.

There is also a lubricant that can be wiped over the seals to them well conditioned. Most toilet manufacturers recommend their own brand of lubricant but most will also recommend an alternative in the owners manual. This is usually a silicone grease (which is safe for all plastics and rubbers) or olive oil.

The other cause for toilet smells may be that someone inadvertently used the toilet while the cassette was removed. This allows waste to go on to the floor of the cassette housing and can pool in the small catchment sumps in the base of the housing. To check this, the next time you remove your cassette, lift the covers to these catchment sumps and look for any accumulated waste. Should there be any, this should be cleaned out with a strong detergent that is safe to use on plastics.

How do you empty it?

Emptying the cassette is very easy and should be done within about five days or as soon as the “Cassette Full” light comes on. When you are ready to empty the cassette, you will need to find a designated dump point to empty the waste. These are made freely available by local councils. To find a dump point, there are a couple of really useful sources of information and most will locate a dump point near to your location. Stay tuned for our upcoming article on the top information sources for caravanning which includes free camping and dump point apps and maps.

Now that you have your dump point, remove the cassette from its housing (either directly under the toilet or accessed from an external access hatch). There is no need to close any valves as this automatically happens when you remove the cassette, but it is always a good idea to check that the all valves are closed properly

If your cassette has a handle and wheels, this will help to take your cassette to the dump point. If you have to transport the cassette by car to the dump point, don’t stress about spillage as these units are watertight when kept well maintained.

At the dump point, simply take the emptying spout lid off, aim the spout down the dump point opening and press the breather valve button and lift the back end of the cassette up to pour the waste out. It’s important to press the button before tilting the cassette as this will prevent a surge of waste emptying at once.

Once the cassette is empty, pour a couple of litres (half a gallon) of clean water into the cassette, refit the spout lid and hold the cassette in the horizontal position. Now gently swish the water inside the cassette to clean the last remnants of waste out and repeat the emptying procedure. Make sure that you aren’t too rough with the swishing as there is a float level switch inside the unit that puts the full light on and if you are too rough this can cause issues with this function.

Hot tip: always keep some hand sanitizer with you when doing this job to ensure there is no hygiene issues when you finish the job.

Now that the cassette is clean and empty, you can refit it to the caravan. The next step is to add the waste holding tank chemical to the cassette. The easiest and cleanest way to do this is to add chemical and a two to three litres of water to the holding tank is through the toilet bowl. Simply open the toilet flap and pour the chemical in followed by the water. And even better way is to have three-litre container with the right amount of water and chemical marked off on the side. This way the mixing and dosage of the chemical is done correctly and in the easiest way possible.

Lastly, make sure fill the flush water tank so you are not going to run out in between emptying times. Again, a two- or three-litre container can be useful for mixing the right amount of chemical to water. You can keep the left-over mixed solution for next time with out having to guess how much you need to mix up to fill your tank.

Do you need chemicals?

The answer to this is absolutely, yes. There are two main chemicals used in these types of systems. The first is in the holding tank and the main purposes of this is to breakdown the solid waste and toilet paper while neutralising the odours. The second is used in the flush tank and this chemical helps to clean and sanitise the toilet bowl while keeping adding a nice fresh scent.

There are some cheaper alternatives to the name brand chemicals and one that will often be mentioned is NapiSan laundry detergent. People seem to have varying levels of success with this product but either way, an additive to breakdown waste and neutralise odours in the waste holding tank is essential to keeping the cassette toilet experience enjoyable.

Is it leak proof?

This is a question almost all first timers will wonder when they have to carry their full cassette to the car or dump point. The good news is yes, these units are made watertight. I have tested this by shaking a full cassette to see if there would be any leakage and there was none what so ever, but one tip is to transport the full cassette in its normal operating position. For most cassettes this will mean it is horizontal and this keeps all the seals at the top of the unit to minimise the likelihood of spillage. The only caveat here is that all the seals need to be well maintained. As mentioned earlier, if seals age without adequate lubrication, they become hard and lose their sealing ability. Simply check these seals each time you empty it and replace the seals if they show signs of hardening or cracking.

The biggest risk for spillage comes from overfilling the cassette. Ideally, the cassette needs to be emptied as soon as the full light comes on but do not fear if it comes on in the middle of the night. All the good manufactures design this light to come on at about 90% capacity. This means you have a couple (but only a couple) of uses before the cassette is at absolute capacity.

Random Cassette Toilet FAQ

• Does it smell? Not if used correctly with the correct chemicals
• Do you need chemicals? Yes… 100% yes. This breaks down the solids and eliminates odours
• Are there alternatives to name brand chemicals? Yes, some people recommend Napisan in the holding tank and suggest water and a few drops eucalyptus oil in flush tank.
• Can you go number two in cassette toilets? Absolutely yes. The toilet chemicals break the solids down to ensure an easy emptying process.
• Can you use regular toilet paper? Yes but don’t use too much as it does take longer than specialised toilet paper to break down.
• Is it easy to empty? Yes but there are a couple of tips that can make the experience better. Make sure you press the breather button before you tilt the cassette and make sure you have some hand sanitizer available.
• How long do you have after the “Cassette Full” light comes on? Most manufacturers design this light to come on when the cassette is approximately 90% of its total capacity. This gives you two or three more uses before it overflows but don’t risk it if possible.
• Can you transport a full cassette in your car? Absolutely. This is often necessary if the nearest dump point is not close to where your caravan is located. The cassettes are designed to be leak-proof, so you should have no problems putting a full cassette in your car but do try to keep it in its normal orientation.
• What happens if your cassette overflows? Most systems are designed that there are some waste catchment sumps at the bottom of the cassette housing. These are located below the cassette in the cassette housing. They are normally covered by lids that will allow any overflow or waste that was flushed when the cassette is out to be captured rather than running down the side of your van. Check these catchment sumps every time you empty the cassette to make sure there are no issues.
• Can you dispose of female sanitary products in the toilet? No, this will likely clog the system as it would in a domestic system
• What is the best lubricant to use for the seals? Silicone grease or olive oil.
• Do you open the trapdoor before or after doing your business? Do this before to reduce build-up on the top of the trapdoor.
• How do you deal with skid marks? Do a pre-flush to lubricate the toilet bowl to help the solids slide without clinging. Use a spray bottle on stream to blast off any skid marks that are left behind.
• How long does a cassette before needing to empty? For the two of us, it is usually three to five days.
• Can you deep clean a cassette if bought second hand or in between seasons? Yes, Thetford sells a good cleaner that works very well but does require 24 hours soaking.
• Can you empty the cassette in to a regular toilet? Yes, but check whether the sewage system is a septic tank system. If so, you can only empty some chemicals in to these systems otherwise you can kill the bacteria that lives in the septic tanks. Just check the label of the chemicals to see if they are septic tank safe. Thetford “Aqua-Kem Pink” and “Aqua-Kem Green” chemicals are septic safe while the “Aqua-Kem Blue” is not.

Hopefully this answers some of your questions regarding the humble cassette toilet  but feel free to add a comment or question below and we do our best to get back to you.