Thetford Toilet Cassette Repair Tips/Advice for Caravans and Motorhomes

Hi, I’m Chris, I run Horton Common along with my father Robert.

At Horton Common, while we do provide fully serviced hardstanding pitches we arent able to provide toilet and shower facilities (Green Belt/Planning, long story). Therefore, all our guests have to be familiar with the Thetford cassette toilet and how to use it. However, nothing lasts forever, and from time to time the Thetford toilet cassette in your caravan made need some attention for maintenance and repair. Therefore, I thought I would write a post to summarise some of the best advice and videos I’ve found on Thetford toilet repairs.

Thetford Toilet Fresh Up Set
If you think your Thetford C250 toilet cassette has ‘had it’, you could consider their ‘fresh up’ set – Image: Amazon

I’ll also discuss (if you don’t already know) how to empty a Thetford toilet cassette properly. Finally, I’ll show the Chemical Disposal Point (CDP) I designed and made here at Horton Common. We have been to some small caravan sites in the past where the CDP was a bin lid covering a hole in the ground. As a user experience, I hated that, but also on a safety level its just ridiculous. This post will cover a range of maintenance and repair topics. Therefore please use the Table of Content below to skip to any particular sections your interested in.

Replacing the Seal on a Thetford Toilet Cassette

If you’re noticing unpleasant smells coming from the bathroom of your caravan or motorhome, it may be that the seal on your Thetford toilet cassette needs attention or replacement. The seal on a Thetford toilet cassette is properly referred to as the ‘lip seal’. It sits tightly against the open and close valve on the toilet cassette and the toilet bowl within your caravan or motorhome.

Why do Lip Seals Fail?

To provide a good seal to keep the contents and smells trapped in the toilet cassette, as you would expect the lip seal is made from rubber. Rubber ages over time and becomes less flexible and malleable. Eventually, cracks will also appear and the lip seal is no longer fit for purpose. Other factors can also age rubber, such as UV. Obviously, with a Thetford toilet cassette contained within the caravan or motorhome for most of its life, it is not exposed to sunlight for long periods. However, when it comes to Thetford toilet lips seals there is the question of the impact of blue toilet chemicals. In any case, the point being, eventually that rubber lip seal is going to need replacing.

How to Repair a Thetford Lip Seal

The best video out there currently that I can find is presented by Dan (Meet the Trudgian) for Practical Caravan. Dan provides a very detailed description of how to open the Thetford toilet cassette. He then shows how to remove the components to actually get access to the lip seal. Finally, Dan shows how to replace the lip seal along with some seal lubricant. If you do need to replace the lip seal on your Thetford toilet cassette I would encourage you to watch the video below. Below I will also add a few more of my own comments.

Dan presents probably the best video currently available on how to replace the lip seal on a Thetford toilet cassette.

Now you have watched the video above I just want to add a couple of my own comments to ‘flesh out’ how I would complete the task.

First, Thoroughly Clean the Thetford Toilet Cassette

Ok, the video doesn’t reference this step, maybe its presumed to be obvious. But the point being, nobody ‘likes’ emptying a Thetford toilet cassette, nevermind opening one up to repair the lip seal. Therefore, before you consider doing open the cassette up to complete the works you will want to thoroughly clean it out. And when I mean thoroughly I meant as you have never cleaned it before. We are talking about repeatedly putting freshwater in the cassette along with some blue toilet chemical or cassette cleaner. Put the screw top lid back on and repeatedly shake the cassette. Then empty it out and do it again, and again. You want to repeat until you are completely confident you can cope with opening that toilet cassette up.

Thetford Cassette Tank Cleaner
Before you approach the job of changing the lip seal you’ll want to thoroughly clean the cassette: – Image: Amazon

Now, there is a caveat to the above advice which you also want to think about. If the lip seal has failed and significantly failed (cracked). During shaking the toilet cassette some of the contents may escape. Therefore, before you complete the above cleaning you may want to use some quality duck tape/plastic bag around the seal. Alternatively, you could place the whole Thetford toilet cassette within a bin bag. Make sure to remember to tie the top before the shaking takes place.

Products and Tools for the Job

Obviously, you’re going to need a new Thetford lip seal. Most caravans and some motorhomes come with the Thetford C250 or C260 toilet cassette. In that case, you’ll probably want the C23721 lip seal. However, its best to never presume and you should make sure you know exactly what Thetford toilet cassette you have and which lip seal you need. You’ll also want some suitable seal lubricant. You may choose to use olive oil or similar, though the Thetford seal lubricant is pretty inexpensive.

Thetford Seal Lubricant
Beside using olive oil to lubricate the toilets lip seal, you could also consider Thetfords own Seal Lubricant spray: Image – Amazon

Besides a set of screwdrivers your also going to want to use a set of gloves. Now, I would recommend some decent disposable gloves to complete this lip seal replacement job. However, in general for emptying the Thetford toilet cassette, I prefer using disposable gloves.

Fixing the Toilet Full LED Indicator

On many caravans and motorhomes which are fitted with the Thetford C250 toilet cassette on the toilet its self, you have an LED which indicates when the toilet is full and needs to be emptied. If you know the toilet is full but the light has not come on, the video below from Dan provides some excellent advice on how you might be able to identify the problem.

If your Thetford toilet full LED indicator is not working you may want to check out this video.

Thetford C250 Float Magnet and Reed Switch

So as you can see from the video above, the first task Dan carried out was to check the magnet in the C250 toilet cassette was still in place using the reed switch. However, as Dan later found out it was the connection on the reed switch where the fault was actually present. Now, if you are not handy with a voltmeter and soldering iron like Dan to fix the problem you can actually purchase a new Thetford reed switch.

Thetford C250 Reed Switch
If you cannot repair a faulty Thetford reed switch you can order a replacement: Image – Amazon

However, the first thing to actually check is that 3A blade fuse. You can check it with a voltmeter but they are translucent. So if you can see a completed S within the fuse its fine. However, if the S is not complete and the fuse is blown you will need a replacement 3A blade fuse. Its handy to have a set of blade fuses. In the past when I’ve been trying to correct a 12V electrical issue with my car I accidentally blew a couple of fuses.

Blade Fuse Set
Its often handy to have a blade fuse set when it comes to resolving car, caravan or motorhome 12V electrical issues: Image – Amazon

Don’t presume the service centre with your annual caravan service will pick up issues with your Thetford toilet cassette. If you cannot fix the issue yourself you will need to bring it to your service centres attention.

Remedy for Toilet Flush ‘Black Bits’

Now, personally, I’ve never experienced this issue and its not an issue any of our guests to Horton Common have brought up before either. However, after watching Dan’s video below I can understand how this ‘black bits’ issue could happen. So apparently if black bits appear when you use the toilet flush pump its bits of algae growing in the toilet flush tank, apparently feeding on the pink toilet chemical.

Apparently, black bits from your toilet flush tank is algae which have been feeding on the pink toilet chemical.

Cleaning the Toilet Flush Tank

So, in my post on how to sterilise a caravans water system which also features one of Dan’s videos the use of Milton in a caravan is discussed. As referenced in that post, Milton can attack metal surfaces and is therefore generally not recommended for use in caravans or motorhomes. The recommended alternative is Puriclean. Are there any metal surfaces in the toilet flush tank or pump? I’m not sure. Therefore, to be on the safe side to clean out the toilet flush tank as Dan shows in the video, you could use Puriclean instead. For this cleaning process to be effective your going to want to leave the Puriclean in the flush tank for at least several hours.

How to stop the Issue Recurring

Dan gives some good tips about draining down the toilet flush tank when not in use. Ideally, you’d also let it ‘air out’ by leaving the filling door open for a while. As Dan states, the use of the pink flush tank fluid is optional. It plays no role in breaking down the contents of the toilet cassette. It is really just to make the experience of using a Thetford toilet cassette in a caravan or motorhome just a bit more pleasant with a nice fragrance. Therefore, using less pink toilet flush chemical than ‘recommended’ may actually be the key to stopping this issue recurring.

Thetford Toilet Pump Replacement and Repair

Now, this issue is one that myself and my father are familiar with as it happened to us. Each winter we drain down the toilet flush tank following best practice to avoid issues with freezing. However, one year, I believe it was 2014, we had a particularly hard winter. When we came to test the toilet flush tank pump next spring it failed to operate. We also noticed water in the toilet cassette locker. After taking out the toilet pump and inspecting it, even though the system was drained it appears a small amount of water remained in the bottom of the pump. During the harsh winter, this water froze and expanded, breaking the seal of the pump. Unfortunately, it was unrepairable and we had to swap it for a new one.

Thetford Toilet Pump
If your Thetford toilet pump fails its pretty easy to get a replacement, however getting it into position can be tricky: – Image: Amazon

Therefore, now for our winter prep, we not only drain the flush tank we actually take out the toilet flush pump itself. Now, it might be the case that your pump is fine but its the control panel itself on the top of the toilet which is faulty. If that’s the case it might be worth watching the video below. Forwarned this is quite a long one (around 19 minutes) but it goes into quite a bit of detail of this caravaners experience correcting the issue with this Thetford toilet pump.

Your Thetford toilet pump may be fine, the issue may actually lie with the control panel on the top of the toilet in your caravan or motorhome.

How to ‘Properly’ Use and Empty a Thetford Toilet Cassette

Now, at Horton Common, I get a wide range of guests from very experienced caravanners to first-timers. Some first-time caravanners are even more knowledgable than some of my frequent guests. However, some have not been instructed by their caravan dealer how to properly empty their Thetford toilet cassette. I wanted to reference the video below from Practical Motorhome on using a toilet cassette to make my own comments.

This Practical Motorhome video I think is the currently the most complete advice on using and emptying the Thetford toilet cassette.

The Vent Button is Important

Quite a few of the first time caravaners that visit our site have discussed with me their issues when emptying the toilet cassette and ‘splashback’. Emptying a toilet cassette is not a pleasant experience at the best of times, but splashback is going to make it even worse. Many first-timers appear not to be aware of the use and importance of the vent button. As any experienced caravanner will know, to avoid splashback pressing and holding down the vent button is essential. With the vent button depressed you can steadily empty the cassette. Avoiding splashback is also helped by a good CDP design (details below).

Blue, Green and Pink Cassette Toilet Chemicals

When I get around to it I will write a roundup post on the different cassette toilet chemicals available. As previously discussed and as referenced in the video above, the pink flushing chemical is optional. When it comes to the blue chemical as the Practical Motorhome video references there are alternatives. In the video a washing machine bio tablet is used, I’ve never personally used this solution so I’m not sure about its effectiveness. However, there are also biological green toilet chemicals.

Thetford Aqua Kem Blue
Personally, in my opinion, Aqua Kem Blue still does the best job of breaking down the contents of the toilet cassette. But I appreciate its not the best product for the environment: Image – Amazon

At Horton Common, our CDP is linked to a cesspit tank which has a special chemical-proof lining, hence its not a septic tank. We have this tank emptied by a waste handler registered with the Environment Agency. The reason I went with this option was before we opened our site we had been on previous small sites with a septic tank that mandated the use of the green toilet chemicals. Unfortunately, from our experience, they don’t break the contents of the toilet cassette down to the same degree. Hence, emptying and cleaning the cassette is more difficult. Therefore with our site, I didn’t want to force our guests into using or not using a certain chemical additive. Just to clarify, I do hope the biological products improve as they are better for the environment.

Thetford Fresh Up Kits

As discussed in the Practical Motorhome video and briefly by myself at the start of this post, you can purchase Thetford toilet ‘fresh up kits’. This is essentially a new Thetford toilet cassette and toilet seat to suit your caravan or motorhome. As described in the video, the fresh up kits are of particular interest to those purchasing a second-hand caravan or motorhome. If you have a caravan the C250 Fresh Up Kit is probably the one you’ll need. And if you have a motorhome its more likely to be the C200.

Thetford C250 Fresh Up Kit
For a caravan, its likely you will require the C250 Thetford Fresh Up Kit: Image – Amazon
Thetford C200 Fresh Up Kit
For a motorhome, its likely you will require the C200 Thetford Fresh Up Kit: Image – Amazon

Our CDP at Horton Common

So briefly at the end of this post, I wanted to reference our CDP point here at Horton Common. We are not just site owners but fellow caravanners. Therefore we appreciate that emptying a Thetford toilet cassette is not a pleasant part of caravanning. So my objective was to make it as simple and convenient as possible. I raised the CPD off the ground and constructed it out of bricks and concrete for durability. Using a large round plant pot I was able to form the bowl shape which helps to avoid splashback when emptying the toilet cassette. I used a hard wearing pond lining paint which creates a smooth surface to aid the emptying process.

Chemical Disposal Point (CDP)
Our CDP here at Horton Common

As standard, a tap/hose is provided for washing out the cassette. However, I also wanted to add some protection from the wind and privacy while our guests empty their toilet cassettes. Therefore I constructed a fence around the CDP which serves that purpose. Since opening in 2014 I’ve received many positive comments on the design and construction of the CDP which I’m really happy about.

CDP Fencing
Fencing around the CDP for protection from the wind and privacy while emptying the toilet cassette.

Anyway, that’s it for today’s post. I hope you found some of the information above useful to fix issues you may be experiencing with your Thetford toilet cassette. I also hope you consider making a visit to come and see us here at Horton Common in the near future. šŸ™‚

Chris - Site Manager

Hi, Iā€™m Chris, I along with my father Robert we operate and maintain Horton Common.

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