Thetford Toilet Cassette Repair For Caravans & Motorhomes

Hi, I’m Chris. About Me

At Horton Common, while we do provide fully serviced hardstanding pitches, we aren’t 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. Therefore, I have a post on how to use a caravan cassette toilet. Within that post, I discuss the various blue, green and pink toilet chemicals available, whether you need to use them and their effectiveness. However, nothing lasts forever, and from time to time, the Thetford toilet cassette in your caravan may need some attention for maintenance and repair. So let’s look at the best advice and videos I’ve found on Thetford toilet repairs.

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

Disclaimer: Hey! By the way… any links on this page that lead to products on Amazon or Caravan Guard are affiliate links, and I earn a commission if you make a purchase, with no additional cost to you 🙂

Elsan ORG02 Organic Toilet Fluid for Motorhomes, Green, 2 Litre
4,751 Reviews
Elsan ORG02 Organic Toilet Fluid for Motorhomes, Green, 2 Litre
  • Dissolves waste and removes odours naturally and has delightful mild fragrance

I’ll also discuss (if you don’t already know) how to empty a Thetford toilet cassette properly. 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 you’re interested in.

Want To Visit Horton Common? – Book Here

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 will no longer be 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 is, 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 is, nobody ‘likes’ emptying a Thetford toilet cassette, never mind opening one up to repair the lip seal.

Therefore, before you consider opening the cassette up to complete the work, 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 up that toilet cassette up.

Before you approach the job of changing the lip seal you’ll want to thoroughly clean the cassette: – Image:

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 in a bin bag. Make sure to remember to tie the top before the shaking takes place.

Products & 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 never to 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.

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

Besides a set of screwdrivers, you’re 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 also prefer wearing disposable gloves.

Fixing the Toilet’s Full LED Indicator

On many caravans and motorhomes which are fitted with the Thetford C250 toilet cassette on the toilet itself, you have an LED that 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 & 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.

If you cannot repair a faulty Thetford reed switch you can order a replacement: Image –

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.

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.

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

Don’t presume the service centre with your annual caravan service will pick up issues with your Thetford toilet cassette.

Though if you cannot fix the issue yourself, you will need to bring it to your service centre’s 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 are algae that have been feeding on the pink toilet chemical

Cleaning The Toilet Flush Tank

So, in my post on how to sterilise a caravan’s 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, you’re going to want to leave the Puriclean in the flush tank for at least several hours.

How To Stop The Issue From 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’ on the bottle may actually be the key to stopping this issue from recurring.

Thetford Toilet Pump Replacement & 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 on the pump. Unfortunately, it was unrepairable, and we had to swap it for a new one.

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

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 about 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 & 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 knowledgeable 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 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 & 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.

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 –

At Horton Common, our CDP is linked to a cesspit tank that 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, green toilet chemicals 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.

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

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

Our CDP At Horton Common

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. 🙂

Want To Visit Horton Common? – Book Here

Recent Posts