Chemical toilets

There’s a lot of confusion over chemical toilets. In their simplest form they are nothing more than a fancy plastic bowl that you do your business in and then empty when it’s full. My nanna used to have a big ceramic chamber pot under her bed. She’d empty it down the toilet each morning as she got out of bed but in essence that’s all a toilet is in a motorhome, but with a few modern modifications. And of course you don’t slide it under the bed. 

Flap opening lever on Thetford chemical toilet
Flap opening lever on Thetford chemical toilet

Firstly inside, this lever under the seating bowl needs to be pushed firmly to the right. This opens the flap which seals what would in a normal household toilet, be the S bend. It allows your stuff to go into the holding tank below, and afterwards when you slide to the left it seals the tank so that no spillages can occur and no foul smells can come out.

It’s best to leave the lid down when you open this because sometimes there’s a build up of gas inside the holding tank and over time this can cause enough pressure so that once you open the flap some of the contents can splash upwards with enough force to actually come clear of the toilet and end up on the floor, or even you. It makes a mess of the lid too. 

It doesn’t happen often but it’s worth thinking about because the earlier you get into good habits the more they will become so routine you’ll do them without thinking. 

Anyway, open the flap, lift the lid and seat and you should be able to look down into the cassette. Mines a C20 and holds about 15 litres. There are various chemicals you can buy, from older types with formaldehyde in that are harmful to the environment, to newer types which are formaldehyde free but may still be harmful to the environment to a lesser degree. There is an alternative which I’ll discuss later. 



Manual flush on a Thetford chemical toilet
Manual flush on a Thetford chemical toilet

The most popular and well known brands are Elsan which has an organic brand, Thetford’s Aqua Kem and Blue Diamond. In my experience there’s not one better than the other.

Chemicals tend to come in blue or green and pink. Pink is for the flush, blue and green is for the cassette. Follow the instructions on the bottle for how much chemical to use but typically you need to put 1 – 2 litres of fresh water in with it and ensure the water level is always covering the waste inside. In the photo to the right you can see the manual flush handle. Pull up slowly and push down slowly to pump the water for the flush. Many more modern vans have a small blue button and this is an electric flush. When adding water to the chemicals it’s easier and quicker to fill from a jug, and you can measure how much is going in.

In the photo below left you can see a small lockable flap above the cassette cabinet. This is where you fill the toilet flush. It’s about 10 litres capacity and you can add flush chemicals when you fill to make it smell nice. Some modern vans don’t have this, they take their flush from the main onboard water tank.

If you use toilet paper try to buy the cheap, flimsy stuff. It’s flimsier than expensive brands but not by much, but it breaks down much easier in chemical toilets, and less likelihood of it clogging the cassette up. I use a minimal amount as I prefer baby wipes which I buy by the box. Baby wipes are one of the most used and useful things you can keep in your van but if using them for the toilet dispose of them in a bag separately, don’t put them in the loo or let them get into the sewage system. Here’s a list of things I use them for.

Outside view of Thetford C20 chemical toilet cassette
Outside view of Thetford C20 chemical toilet cassette

The small light at the right tells you when the cassette is full and needs emptying. You’ll be able to tell anyway, don’t let the level of toilet content reach the flap or you risk spillage. I empty mine at the latest when it’s 1 inch from the level of the flap. 

Emptying the cassette is really straightforward. In the photo to left you see two yellow items: the bottom one is a retaining clip, you simply lift it with your hand as you pull the handle above it and pull forward and the cassette will slide free toward you. The cassette automatically seals itself when you slide it out. The yellow cap is on the end of the emptying tube which can swivel and you simply take that cap off and empty the cassette. Bear in mind if your cassette is 15 litres capacity, that’s over 15 kilos in weight!

Note that you must ensure the flap in the toilet is tightly closed or the cassette will not come out. 

Pressure release valve on the Thetford C20
Pressure release valve on the Thetford C20

Once you get the cassette out, as you empty it you must hold down the small yellow button as shown on the right. This is an air valve and ensures the contents can come out without a problem. It’s best to turn the cassette upside down and give a small shake first as that helps solids and toilet paper to come through the emptying tube more easily. It might sound complicated but after a few times of doing it it will become second nature.  


Alternatives to chemicals

Chemicals can be expensive and for some time now I have used bio washing tablets in my toilet. I prefer Tesco jasmine ones simply because they smell lovely when you’re at your business. They work out much, much cheaper too, I use 1 tablet per fill in winter and 2 in summer and generally speaking I empty my toilet once every 10 days or so. The tablets smell great, they break down waste and they’re less harmful to the environment than some of the chemicals. They’re more easily available too and as I use laundrettes exclusively for my clothes washing I always have some in anyway. 

Many people favour the Aldi brand Almat. I’ve tried them and they work no better or worse than others but sometimes are cheaper. Tablets are of course much easier to store than great bottles of fluid and weigh a lot less. There’s some good advantages to using them.


The interior area of the bathroom gets very dusty, partly because there’s a vent in all bathrooms and because it’s a road vehicle they’re susceptible to dust, so check under and around often for dust and grime. I use nothing more than a drop of fairy liquid in warm water, rinse and then polish with wax free Mr Sheen. The Mr Sheen discourages dust to stick and keeps it looking shiny and new for longer. Small water splashes are easier to clean too. 

My bathroom is also a shower so it’s designed to be waterproof so if I’m near a hose I often open the window and simply hose everywhere up to waist height to get rid of dust and dog hairs etc. It’s simple to sponge down afterwards then polish the plastic .

It’s best to keep the outside case of the cassette as clean as you can too. Again I use a small amount of Fairy liquid in warm water and rinse but I know some like to use anti-bacterial products. Just make sure what you use is not harmful to types of plastic. Once in a while it’s advisable to fill your cassette with hot water and some cleaner and let it soak to ensure it’s thoroughly cleaned.

Going totally chemical free 

You can go totally chemical free by fitting a SOG system. Put simply it’s a fan that operates when you open the flap and sucks air out of the cassette and through a carbon filter to the outside of the van. In theory there’s no smell escapes at all and you can use your toilet completely chemical free. 

You can find out all about SOG kits here and make your own mind up. 

Emptying your cassette toilets

There are many discussions online in groups and forums regarding the emptying of chemical toilets which usually get quite fraught. Some people think it’s OK to empty them even at a layby on a public road as long as they go into the bushes. It’s not acceptable at all, the stench is putrid and families sometimes stop at laybys with their kids to break up a journey. Can you imagine playing footie with your child and sliding into 15 litres of foul smelling human waste?

Others think emptying them into rivers is OK as the water dissipates the waste. But all you’re doing is adding waste and poisons to fresh water and if some solids and paper have not broken down these are added to the environment. It’s no good saying “Cows do it in fields!” We’re not cows with a plant diet and it’s just not acceptable or legal. Toilet waste is classed as black waste as it is hazardous. If you are going to bury it as some do it must e a minimum of 100 metres away from any public area or water course.
Grey waste, or the water from your tank connected to your sink and shower which is collected in a separate tank, is less harmful and can be sensibly drained in areas by thoughtful people.

Emptying into public toilets is also not a great idea. It’s extremely difficult to empty a toilet cassette without having splash and I for one don’t want to go into a public toilet and see stale, foul smelling waste splashed all over. Besides many public toilets, especially rural ones are now composted or use septic tanks and emptying such waste into them prevents them from working properly. 

A lot of campsites now allow you to use their facilities for a short period of time for a few £’s. This includes emptying your waste and it’s advisable to do this. Rinse the cassette several times after emptying to make sure as much waste as possible is gone and leave a litre or 2 of fresh water in there when you’re done. Join some motorhome groups and forums and there are any amount of people who will advise you where to go. If you can’t find a site that allows temporary access consider a cheap site for a night. You can shower, use laundry facilities, charge your batteries on electric, fill up with fresh water and chat with other people as well as emptying your toilet. 

The Caravan and Motorhome Club have small and friendly Certified Locations which may be cheaper. The Camping and Caravanning Club has a similar scheme too. When abroad there are a huge amount of dedicated motorhome areas which allow an overnight stay, emptying of black waste and filling with fresh water mostly for free or just a couple of euros. Again, a good group will help you out with endless knowledge. 

Remember human waste is foul smelling and poisonous, dispose of carefully, thoughtfully, properly, and legally.

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