A guide to RV cassette and composting toilets
A loo on board can make the caravanning lifestyle easier, but there are some downsides. John Hughes provides a comprehensive guide to key differences between cassette and composting toilets and provides some insiders tips and tricks to make your life on the road more enjoyable.
There are many benefits to having your own loo on board. It prevents a traipse (or dash) across a caravan park in the middle of the night to use the public facilities. It can take the hassle out of finding a public toilet on the road if you are in a hurry. But the downside to having a loo on board is that you have a loo on board and that means you need to deal with disposing of the contents. It isn’t completely gross, but it isn’t exactly the most fun job either. We will arm you with some information to minimise the ‘not fun’ aspect and share some of my anecdotes of what not to do! Broadly speaking, there are two toilet types — cassette toilets and compost toilets. Let’s go through them.
Cassette toilets
How do they work?
Most of the loos you see in Aussie vans are cassette toilets. They have proven to be functional and reliable over decades. They look a lot like your toilet at home and you use them pretty much in the same way. The main difference is you don’t have water permanently sitting in the bowl — imagine that sloshing around as you were driving down the road. Instead, you have a ‘dry’ bowl with a trap door in it that you flush after doing your thing. The flushed water and waste go into a storage tank underneath the bowl. The storage tank is known as a cassette and is accessed externally via a hatch.
Some toilets are permanently plumbed to a cistern like your toilet at home. Other toilets have cisterns that you manually fill through an access point in the external hatch.
The cassette in a Thetford toilet
Emptying the cassette
When the cassette is full you need to open the external hatch, release a catch and lift the cassette out. The cassettes can be quite heavy, so they have wheels and handles very similar to a suitcase to make them easier to move from point A to B. Your destination is a designated dump point to empty the cassette. The process involves swivelling out the cassette spout, removing the spout lid and pouring out the sloshy contents of flush water, human liquid and solid waste and toilet paper. An important step is to press a button to open a little breather valve that enables air to get into the tank, so the pouring process is quicker and smoother. It’s the same idea as using the breather when pouring fuel or water from a jerry can. After emptying the tank, you give it a rinse by adding a bit of water, gently sloshing it around and then pouring it out.
Chemicals
The main reason this whole process isn’t completely gross is because you add chemicals into the mix. You start with an empty, clean cassette and then add a prescribed amount of water and chemicals into the cassette through the swivel spout. You then insert the cassette into the holder, and you are ready to go.
Thetford has its own brand of chemical
So, what do the chemicals do? According to the Thetford website, they help in a number of ways. They promote the solid waste and toilet paper to dissolve into a liquid. I can tell you from personal experience I have tried cutting corners when I have been out of chemicals and it ain’t fun. Emptying liquified contents out of a tank is a lot easier than dealing with blockages at the spout caused by solid waste and toilet paper. As an aside, Thetford offers a specific toilet paper that breaks down more readily than regular toilet paper. The chemical also helps to neutralise/mask the smell and reduce gas buildup. Toilet chemicals come in a variety of formats. There are liquid and dissolvable sachet versions, and some are more potent than others. Some versions are not recommended for dumping into septic tanks because they kill off the ‘good bugs’ that help break down waste. If you always empty at a designated RV point, then there is no problem. However, if you are emptying into a facility that uses a septic system then you need to select a chemical that is septic friendly.
How often do you need to empty the cassette?
We debated internally if you could nominate an average time between cassette empties and concluded you can’t. I have had occasions with my wife and I and four small kids where I was emptying practically every day. Colleagues have reported they can go over a week. This is what we can tell you. A typical cassette tank has around 18–20L capacity. You lose about 2L of that capacity when you add clean water and chemicals after each dump and clean. We guess the average flush of just the fresh water is about 0.3L. The rest is up you and what goes in there and how often. An even more important thing I can tell you is to pay attention to the cassette level indicator. I have paid the price of ignoring this and had the nasty job of cleaning out overflowing contents from the hatch where the cassette resides.
If you are off-grid or going on road trips into remote areas one way to double your ‘range’ is to carry a spare cassette if you can find a sensible place to store it.
Maintenance
I mentioned earlier the cassette has a trapdoor which keeps the contents contained and minimises odour escaping. The trapdoor seal needs to be lubricated from time to time to ensure smooth operation. And here’s some motivation to stay on top of it. A few years ago, we went on a motorhome trip around Europe with the kids. The trapdoor was becoming difficult to open so I got down on my hands and knees for a closer inspection and to apply a bit of force. I succeeded in opening the door, but I received an interesting surprise. We had started travelling that day at a low altitude and climbed quite high up in the Alps. As you climb atmospheric pressure drops and the relative pressure in the sealed cassette rises. As I released the trapdoor, I was splattered in a small burst of toilet contents!
Composting toilets (separation toilets)
I reviewed a van from high-end, custom manufacturer Lyfe RV some time back (issue 634), and I recall they were very keen on compost toilets. I gave Lyfe RV director Danni Tedesco a call to enlighten me further on why. She reckons: “Once you have tried a composting toilet you will never go back. We have used cassette toilets on many extended trips in the past and they do the job, but compost toilets have so many advantages. We are custom builders, so we offer our clients a choice of whatever toilet they like. Once we educate them virtually all of our customers go compost. Our two preferred compost toilets are the OGO and the Separett Tiny. My favourite is the Tiny. In my view, it is the more aesthetically pleasing loo and more importantly, the functionality is much easier. The alternative, OGO, is very effective, but it is a more complex system. Another popular brand is Nature’s Head.”
Check out this review of the Lyfe RV19F Off-Road caravan which features a Separett Tiny urine separating toilet.
A bathroom with a Thetford toilet and vanity basin
How do they work?
Armed with these insights from Danni, I explored these systems fuxrther. In a general sense, all these toilets have functionality in common that differentiates them from cassette toilets. The two most important things are:
- There is no water flushing involved (i.e., it is a waterless toilet).
- They separate human solid and liquid waste into different receptacles.
No flushing is significant for off-grid camping on a couple of fronts. Your fresh water supply will go further because you are not flushing it down the toilet. And you won’t need to empty your toilet waste receptacles as often because you are not filling them up with water.
The OGO, Separett Tiny and Nature’s Head all have a urine diverter that connects to a separate container under the toilet seat. The Separett Tiny directs the solid waste into a disposable plastic bag. The OGO directs solid waste into what is essentially a removable bucket. The Nature’s Head captures the solid waste in the toilet base. The OGO and the Nature’s Head require coir peat (also known as coconut coir, which is made from coconut fibres) and a small amount of water to be added to the solid waste receptacle. The OGO and Nature’s Head both also have agitators to mix the solid human waste and coir peat to help break down and dry out the waste. None of these separation toilets use chemicals like those used in cassette toilets.
The Nature’s Head composting toilet has separate containers for liquid and solid waste and an agitator that breaks down solid waste with coir peat. It is necessary to remove the toilet from the van to empty it which can be a bit cumbersome
All these toilets achieve separation of solid and liquid waste by having two separate openings. The opening at the front receives liquid and the opening (with a closeable hatch) at the rear receives solid waste. All systems require males to sit on the toilet rather than stand to reliably direct waste to the correct opening.
Separating solid and liquid waste has a couple of important points too. You have less odour to deal with because apparently combining liquid and solid waste in the same container (as per the cassette) contributes to a much more unpleasant smell. The OGO, Separett Tiny and Nature’s Head all further reduce the smell by running an extraction fan over the solid waste to dry it out and evacuate odours.
The OGO compost toilet has a minimalist look and liquid and solid wastes are separated; A ventilation system extracts odours
Waste disposal
In all systems, the urine bottle is removable so the contents can be poured out. This can be done at a designated dump point or dump station. When off-grid, it appears it is acceptable to dispose of urine on the ground if some common sense and respect for waterways is used.
As the separated, dried solid waste isn’t that stinky it can be transferred into bigger plastic bags and stored. The emptying process is a little different for each system. The Separett Tiny is the most minimalist where you just remove a plastic bag, tie it off and store or dispose of it. The OGO requires the removal of a bucket-like receptacle which you take outside and then transfer to a dump point or into a plastic bag for disposal later. The Nature’s Head is perhaps the most cumbersome in that you need to remove the complete toilet from the van to empty the contents from the toilet base into a dump point or plastic bag. It’s not as dramatic as it sounds but I would suggest it isn’t that user-friendly.
Being able to bag your waste means you can extend your off-grid stays unlike when a full toilet cassette triggers a trip back to civilisation. When you do eventually get back to civilisation with your bagged solid waste it is acceptable to dispose of it with regular rubbish. It sounds a bit impolite, but it is no different than how disposable nappies are dealt with. Again, just common sense and respect need to be exercised.
Misnomer
Now would be a good time to address that in the context of caravan use calling these styles of toilets ‘composting’ is largely a misnomer. Separating toilets were first developed for land dwellings not connected to sewage or septic systems. In these installations, urine is diverted outside into a diluting tank which can be distributed on the garden as a fertiliser for non-edible plants. Solid waste is captured in a receptacle which is then transferred to a compost bin. This solid waste needs to sit in the compost bin for about a year before it can be used in the garden for non-edible plants. When you are travelling you would very rarely have the opportunity to transfer solid waste to a compost bin.
The wrap
Nearly all new caravans these days will have a bathroom with a convenient toilet. Cassette toilets are the conventional solution, and they do the job well (and for those without one already, there are portable cassette toilet options available that can be stored outside of the van). Learning to empty the cassette is a caravanning rite of passage. It’s something that has to be done fairly regularly and is not too much of a drama if you have access to a dump point. As off-grid camping has become more popular caravan users are looking for solutions to be able to extend their time away. Compost toilets are a great option, and one that is becoming increasingly popular as they provide viable solutions for managing waste for longer. If you are in the market for a new van, it Is worth giving some consideration as to your personal preference and what will work best for your camping style.
Thanks to Thetford for providing background information and images for this article. Learn more on the Thetford website here.
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