Chemical Cassette Toilets

Handy Information for Newbies and People Renting Motorhomes

What is a Cassette Toilet?

Motorhomes come with built in toilets in the washroom. These toilets have a cassette waste holding tank. You can normally remove the cassette from the outside of the motorhome, as it’s stored behind a locked panel. Inside the washroom, the toilet may have a swivel bowl to make the most of a tight space, and the flush may be electrically powered from the unit’s leisure battery or by using a camp site's electric hook-up.  Just to give you a general idea of the tank volume. If a couple used a cassette toilet (never using any campsite facilities) they would probably fill a 20 litre tank in about three days.


Why do some people call it a Chemical Toilet?

Chemicals can be used in a cassette toilet and they work in different ways. Some kill bacteria while others use a biological action to break down waste material. Some mask any smell with perfume and most combine a bit of each. These days, there is a good choice of formaldehyde-free chemicals that are much less damaging than the ones that used to be available. The bottle should describe the contents so check, ask the supplier or find this information online. New toilet fluids use enzymes and natural substances, which aid the decomposition of the waste and are better for the environment.  Some camp sites may request that you use only "organic" or "environmentally friendly" chemicals. Others are able to accept any fluids into their Chemical Disposal Point. The main toilet chemical goes in the unit’s waste tank. These chemicals come in a variety of forms. The traditional type is usually a blue or green fluid, which needs water to dilute it.  If you use a flushing toilet you may also want to add a chemical to the water in the flush-water tank. This is sometimes referred to as the ‘pink’ chemical, after the colour of the early flush-water tank fluids came in.


Where Can I Empty the Cassette Toilet?

The first rule of chemical toilets is that you must only empty them in a specifically designated place. Apart from the obvious hygiene issues, the chemicals should not go straight into the sewerage system because of the biological chemicals in some of these liquids.  They cannot be broken down, and they cause problems at the sewerage works.  On a campsite the place to empty your cassette will probably be marked as a Chemical Disposal Point or CDP. On some sites, it might appear as an Elsan Point.  If you are wild camping in the Highlands and Islands, there are chemical disposal points or CDP's at Ferry terminals. They also have water standpipes to fill your water tank. The larger terminals have showers and other facilities available too.  Good ones like the one shown have a sink for washing your hands and a hosepipe for rinsing.


When can I empty it down a normal Toilet?

If you are not using chemicals at all then you could in theory empty your cassette into the sewage system without doing any harm.  There is a lot of controversy around using public toilets to empty your cassette though. It is difficult to do this without a hose pipe so it can be unhygienic and messy. If you can lift a manhole cover to a sewer (Not a Surface Water Drain!) then it might be a little easier but you will still struggle to rinse it out adequately if you are using it for solid waste as well as liquid waste.  Some campers advocate adding an Eco washing liquid or powder to the waste tank but I have never tried this so cannot comment at how effective it would be at keeping your tank clean. Clearly it wouldn't be a problem for the sewers as we all use washing powder in our machines at home.  

Blue, Green or Pink?

The Blue chemical fluid is the most powerful additive you can put in your waste water tank. The Blue chemical stimulates the breakdown of waste, prevents gas build up and keeps the waste-holding tank smelling fresh. This can only be emptied down a Chemical Disposal Point.  It used to contain formaldehyde but most brands no longer do. The Blue chemical is better at breaking down solid waste.

The Green chemical fluid is like the Blue, it is also a toilet additive for the waste-holding tank that reduces gas build up and suppresses unpleasant smells. However, the Green is environmentally conscious and is suitable for disposal into septic tanks so it is more gentle than the Blue version and lasts slightly less longer.  It is also not as effective in breaking down solid waste and toilet paper.  Some camp sites on the NC500 can only accept Cassette waste with Green fluid as they have a septic tank. Clachtoll is a site that will not let you empty your cassette if you used the Blue chemical so check before you empty!


The Pink chemical does not go in the waste tank. It is added to the "flush" tank. This has a fragrance so it keeps your toilet smelling fresh when you flush. These days you can also find Green liquids that go in both the flush tank and the waste tank.


Do I have to use chemicals?

No, while they do make things smell nice we all know that chemicals are bad for the environment.  The Blue ones are also bad for the public sewage system which is why you cannot empty them in a normal toilet.  Some people choose not to add these chemicals so that they can empty their cassette into a normal toilet. This is fine, but we prefer to use a proper waste disposal on a camp site as it is easier, and you will have access to a hosepipe for rinsing and refreshing your tank.  If you want to do this on a regular basis you should consider installing a SOG system in your motorhome.


SOG kit Toilets CAN be emptied in a normal Toilet

A Sog toilet kit dispenses with the need for smelly chemicals being used in your motorhome  toilet system. Opening the toilet valve activates a low powered extraction fan which consumes a tiny 0.43 watts. The fan creates a mild negative pressure within the cassette which draws oxygen into the cassette from the bathroom area.  This drawing in or air effectively seals off odours contained in the cassette and draws into the cassette personnel odours during use. The sog fan only operates when the toilet is in use.

SOG systems provide a sealed pipe for odour and pressure to passively release, via a charcoal filter, to the outside of the motorhome.  The underlying principle of SOG ventilation systems is the passing of oxygen over the surface of the waste, whether this is accelerated when the fan is in use or passively as pressure escapes from the cassette via the SOG piping system to the outside of your vehicle. This is the natural curing “oxidisation” process used by Sewerage Treatment plants.  Naturally treated waste has far less smell when emptying the cassette, it cannot damage septic tanks or water treatment works and you can use normal toilet paper.

How do I empty the Cassette?

The waste is stored in a sealed cassette. The key to emptying this without spluttering is to press the air-valve button, allowing air to flow into the cassette while the waste flows smoothly out. Your unit’s instruction manual will show you how to locate this button. 

Here is a You Tube Video demonstrating how to empty, clean and replace your toilet cassette system.   

Keeping the Bowl Fresh

Some campers advocate pressing the flush before using the toilet. This adds water to the bowl and prevents "adhesion" to the bowl. I also saw this ‘delicate’ tip online, I saved the picture to show my kids and the coloured paper demonstrates the technique well! 

When using your chemical cassette toilet for "solid" waste disposal, you can help keep the bowl clean by lining it with three pieces of toilet paper before you use it.  When the toilet is flushed afterwards, the paper disappears into the cassette below with the six leaf-like petals of a flower closing neatly around the "deposit".  It is a great tip so I thought I would share it. 



Toilet Tissue

Toilet chemical suppliers recommend that you use ‘quick dissolve’ toilet paper.  This paper is very overpriced but If your family uses a lot of paper this might be a good idea.

In most cases normal toilet paper will be fine and it will certainly be a lot cheaper.  However, thick luxury toilet tissue will clog up your system quite quickly if you use a lot of it. Using quick dissolve paper or perhaps a cheap budget brand which can work just as well as the dissolving type is probably the best idea. You don't want to end up leaning over the disposal point  trying to remove a revolting lump of smelly blockage from your cassette!