How does a caravan toilet work
A practical guide from Caravan Information Services
Caravan toilets may not be the most glamorous topic. But when the heavens open at the campsite or you get caught short camping off-grid, it helps to know how everything works.
But with some toilets needing chemical additives, some additives being toxic, some not, and some toilets being classed as eco-friendly, what are the choices?
This guide explains the difference between chemical and non-chemical toilets, cassette and SOG toilets, vacuum toilets, and portable flushable toilets.
Chemical caravan toilets
Cassette toilets
Cassette toilets are typically fitted to most new caravans. The toilet is built in, and the cassette or waste tank sits behind a locker door outside the caravan.
You flush the toilet by operating a lever or electric push button on top of the cistern or by turning a serrated cap. Most new toilets use the lever or push button. There will also be a mechanism to open a trap door and let waste through into the cassette.
Odours are prevented from returning through the system by adding a chemical additive to the cassette that breaks down the waste and masks odours. You can also add an additive to the flush water that cleans the toilet bowl and releases a scented fragrance.
Emptying a cassette is as simple as disconnecting the unit from the caravan and releasing the contents into a suitable disposal point.
Once empty, cassettes need rinsing with fresh water and new diluted chemicals added before reconnecting to the toilet system.
Top Tip! Emptying your cassette when it reaches two-thirds full can also help prevent odours from returning through the system.
Portable flushing caravan toilets
Portable flushing toilets are used where a caravan doesn’t have a fully fitted system. These units have a built-in refillable water flush tank, toilet bowl and lid mounted onto a detachable waste holding tank.
Emptying the waste involves:
- separating the waste tank
- carrying it to a suitable disposal point
- releasing built-up gases by pushing the pressure release button
- emptying the contents
Non-chemical toilets
SOG toilets
SOG is a high-performance fan and filter system often used with a cassette toilet. In this case, the fan switches on when the toilet valve operates, creating a negative pressure in the waste tank, which sucks the waste through the system.
Instead of chemicals, SOG systems mix air and water to compost waste organically. Then, they ventilate outside via a carbon filter that removes odours.
SOG toilets save the money you would otherwise spend on chemicals and are considered environmentally friendly.
Vacuum toilets
Vacuum toilets are a type of cassette toilet usually only fitted on larger caravans. The toilets work by storing energy, which creates a vacuum. Then when you flush the toilet, the vacuum sucks the water and waste through a pipe into the waste tank.
Vacuum toilets don’t use chemicals, but they are fitted with a filter that needs replacing every one to three years.
Toilet chemicals
There are chemicals to clean and disinfect your toilet bowl and others to break down solids in the waste.
To make life easy, chemical manufacturers colour toilet additives pink, blue and green, depending on the product type:
Pink chemical (flush tank additive)
If your toilet operates from a flush tank instead of a direct water feed, you can add a pink chemical to the tank to:
- clean and disinfect the toilet bowl
- add a fragrance to keep things smelling fresh
- lubricate the seals and extend the toilet life
Blue chemical (waste tank additive)
Blue chemicals contain enzymes and biocides that help break down waste tank solids. These additives also include inhibitors to prevent bacteria and microorganisms from growing in the tank. Some products also contain fragrances to help mask unpleasant odours that can occur during decomposition.
However, blue additives can also contain toxic formaldehyde, the same chemical used in embalming.
Formaldehyde is good at killing bacteria and breaking down waste quickly. But it also kills the bacteria needed for decomposition in septic tanks and large-scale water treatment plants. Not all campsites allow you to dispose of formaldehyde-based chemicals, so double-check the packaging before purchase.
Blue additives are typically more potent than green alternatives. And they also last longer in the tank. But look for formaldehyde-free versions such as Pro-Kleen and OLChem where possible.
Green chemical (eco-friendly waste tank additive)
Green additives use organic, biodegradable chemicals to break down waste solids. They are the perfect choice for eco-conscious campers and are welcomed at all campsites.
Green chemicals demopose waste naturally, but this takes slightly longer than alternatives containing harsh chemicals.
You can also use some products like Elsan Organic and Aqua Kem Green in the flush and waste tank, so you won’t need to worry about pink cleaner.
Cassette tank cleaner
Products like Thetford Cassette Tank Cleaner are additional treatments for descaling, de-greasing, and cleaning your waste tank. They keep the float valves working correctly and protect the rubber seals. We recommend using a cassette tank cleaner every 6-12 months.
Preparing caravan toilets for use
Some caravans have a flush tank filler behind a flap above the main cassette locker door. Others have the filler located directly above the tank.
Check the flush tank capacity before filling to know how much pink or combined cleaner to add before topping the tank with fresh water.
Next, remove the cassette or waste tank and add the correct amount of blue or green chemicals. Dilute the chemicals by adding water in line with the manufacturer’s instructions.
Finally, ensure the filler cap is securely tightened and put the cassette back into the locker.
Now your toilet is ready for use.