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CASSETTE TOILET.
Toilet Techniques
Thetford manufacture toilets for the smallest panel van conversion up to the largest coachbuilt and they are built to last. That said, they do require some basic maintenance from time to time and a little knowledge is a useful tool. The information below applies to pre 2007 models as these are the most likely to need attention at this point in time.
What if something does go wrong?
It is very unlikely that you will need to renew components on your cassette toilet, nevertheless, occasionally the unthinkable does happen and parts could need replacing. The most likely, although extremely rare, failures will be the rubber seals on parts of the holding tank and maybe the pump.
Most of the jobs are similar on the bench and swivel toilet cassettes but we will show the differences where appropriate. Of course, it is essential to be scrupulous with hygiene when undertaking any jobs with the holding tank and the use of rubber gloves is advised. Please note that the cassette used for the photographs was brand new which is why Chalky wasn’t wearing hand protection.
The lip seal
The most common component that you are going to replace is the lip seal, which could fail if incorrect products have come into contact with it. Make sure you order the seal for your particular cassette (swivel or bench) because they are different.
1. Ease off the screw covers on the swivel cassette to expose the screws.
2. Undo the screws in sequence and place them to one side in the order that you take them out.
3. Take off the cover to expose the seal. Note which way up the seal is so that you insert the new one correctly.
4. Lift out the worn seal and replace it with the new one.
5. Put the cover back on and screw down evenly, and finally (swivel cassette only) refit the covers by pushing them on until they click into place.
The spout ‘O’ ring
If you notice a leak at the base of the spout, then it could be because the ‘O’ ring needs replacing.
1. For the bench cassette, turn the spout fully anticlockwise and the spout will pull out.
2. For the swivel cassette, turn the spout fully and then move it back about an inch (3cm). Don’t try to forcibly remove the spout because it will lift out quite easily when it is correctly positioned.
3. Remove and replace the ‘O’ ring.
4. Slot the spout back into the hole and return it to its stationary position.
Air release valve
This is the button that you push while emptying the cassette. If you experience a problem, then it is probably better to replace the whole valve unit rather than individual parts that could become damaged while being extracted. The job is much easier on the bench type cassette because the valve is in a separate casing.
The air valve comes in three pieces: the yellow button, a spring, and a bottom valve. Don’t try to take them apart unless for some reason part of the mechanism has broken. Once the new piece has been inserted and the three parts pushed together, it is very difficult to take them apart again. This is because there are protruding ‘ears’ on the bottom fixing that slot into holes on the button stem; they must be accurately lined up to enable the pieces to lock into place.
1. Bench models: Turn the protruding casing anti-clockwise until it comes to a natural stop.
2. Very carefully put a thin screwdriver between the flanges and gently ease the unit up. It can then be lifted out completely.
3. It the rubber seal is faulty, just replace it and re-insert the casing.
4. To replace the valve, separate the three pieces (described in the introduction to this section).
5. Locate the three pieces into their correct positions in the valve unit and push together.
6. Re-insert the valve unit and lock into place.
7. Swivel models: The valve is set flush into the holding tank and is not in a separate housing. You will need to remove the lip seal cover (as in task 1) to enlarge the access point.
8. Push down on the button from the top whilst locating the valve inside the holding tank, hold it tight and pull off the yellow button; this will be difficult if the valve stem is not the damaged component.
9. Insert the new valve (from inside the holding tank), place the spring on top (outside the tank), line up the holes in the button stem with the protruding ears on the valve stem, and push firmly together.
Automatic vent seal
Again, it is highly unlikely that you will ever need to replace any part of this valve, however, you may need to clean it on rare occasions. It is the same procedure for both models.
1. Turn the valve anti-clockwise until it stops.
2. Extract the valve, clean it or replace the rubber seal if necessary.
3. Put the valve back into its slot and turn fully clockwise.
To replace the vent seal
The seal itself looks like a cup and saucer with the thicker rim of the seal facing towards the top of the tank (cup) and the thinner (saucer) facing towards the bottom.
1. Open the blade and push the vent seal completely through the aperture. Once through the vent aperture, the seal will open up and be resting on the vent block, and appear to be in the correct position.
2. Once this stage is achieved, it is necessary to locate the seal into a groove moulded into the underside of the holding tank. To do this, place one hand inside the holding tank through the blade hole and feel for the plastic block beneath the vent hole.
3. Push upwards firmly, seating the seal into its correct position.
Electric pump (bench cassette)
If you don’t use the cassette toilet for several months it is possible that the propellers may stick, or indeed, the pump may need replacing. The pump is located in the main housing under the toilet roll storage facility. Turn off all electricity supplies before attempting to work on the pump. Of course, the C200S & CS swivel cassettes draw water from the main tank and don’t require a separate pump.
1. Remove the toilet roll holder, by holding the top rim with two hands, and with a twisting action pull it upwards and out.
2. The pump is located at the bottom of the reservoir and you just need to remove the retaining screw to lift it out. We found it easier to remove the flush tube first.
3. To check the propellers, very carefully insert a small screwdriver up through the base of the pump and try to rotate them; they should move freely.
4. To change the pump, disconnect the flush tube (if you haven’t already done it) and cut the feed wire about two to three inches away from the pump
5. A new pump comes with wire connectors, firstly ensure that the shrink tube is placed over the power cable before connecting the new pump. After joining the wire connectors correctly, push the shrink tube over the connections and heat seal the tube by means of a hair dryer or similar device to ensure that it is water tight, then re-connect the flush tube.
6. Check the new pump works and then screw it into position.
7. Replace the toilet roll holder by pushing it firmly into place.
Note. If you are in any doubt about your ability to deal with electrical problems, please get your local motorhome dealer to replace the pump. Remember to check all fuses and the old pump before purchasing a new one.
General maintenance
There is very little to go wrong with your cassette if you follow the instructions in your manual and use the correct chemicals. Thirty years of research and development have guaranteed that Thetford products not only provide optimum performance, but also respect the environment.
Summer or winter, hot or cold temperatures, Aqua Kem performs without fault – providing, of course, the correct dosage is used. For normal all-day use, add Aqua Rinse to the water tank (only models that have a separate water supply), so that after flushing, the bowl is kept fresh and stains are prevented from penetrating the plastic surface.
Thetford produce a cleaning product that is suitable for all types of plastic surfaces, which is great because it means that you only require one product to clean the whole toilet compartment, and it contains nothing that will damage the toilet seal.
It is essential to lubricate the seal and blade periodically to keep them in good working order, especially if you put the motorhome to bed for the winter, or even if you don’t use it for a few weeks. Never use Vaseline (or any similar product) because it contains substances that can cause an adverse chemical reaction, thereby effecting damage. It is preferable to use Thetford Maintenance Spray as it won’t damage the seal and can be used to lubricate hinges, door locks and the like.
You shouldn’t need to use anti-freeze in your cassette as Aqua Kem will protect it if the temperature drops to around -17°C, while the environmentally-friendly Aqua Kem Green is efficient down to temperatures of -20°C. Nevertheless, if you feel safer with anti-freeze during sub-zero temperatures then make sure it is a brand containing the following properties: ethylene glycol, mono-ethylene glycol, propane-diol, glycerol, ethane-diol, glycol. Never use alcohol-based anti-freeze (methanol, ethanol, and iso-propanol) as these could damage the seal and holding tank.
And finally
By taking care of your cassette toilet and by using the correct chemicals, you should not experience any problems. If you follow the manufacturer’s instructions properly and only use the recommended products, then you can almost certainly have many years without undertaking any of the DIY tasks described above. Most of all, our advice is, “If it ain’t broke, don’t fix it”.
Don't forget to mention that you found this information through the World of Motorhomes Website.
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