Dometic and Thetford Cassette Toilet Common Problems

Right after buying our first caravan, we met some concerns about the reliability of some parts of our new purchase. For some of them, we described to you our review of the Eriba Troll 530 model, but some were hard to identify quickly.

One of the biggest doubts of every traveler is personal hygiene, warmth, and of course the toilet. In modern caravans, cassette toilets are increasingly being installed and this is very convenient. We wrote about their principle of work, the smell, and the sizes of the most popular models in this article. Here we decided to collect the most frequent problems that the owners of such toilets face and, most importantly, their solution!

The toilet does not flush?

Don’t be too quick to overestimate the scale of the problem. This is probably one of the most common problems both with Dometic and Thetford cassette toilets.

1. Check the fuse for your toilet.

You should start by checking the fuse. Most often it is 3A or 5A. Even if visually the fuse looks intact, it should be checked, replaced with a new one, or swapped with the working one.

2. Flush water pumps failure

If replacing the fuse does not fix the problem, then the next step is to check the flush water pump. It is located in the tank itself and often has easy access. Check the manual for your toilet model for easier location and access.

Before concluding that the pump is not working, make sure that the pump impeller is not blocked. This happens quite often and requires only slight effort. Use a screwdriver or awl and rotate the pump impeller.

Access to the blocked impeller in the Thetford cassette toilet

The pump could burn out and then it will need to be replaced. Contact your local dealer for an original spare part, order on Amazon, or find an equivalent. Such a pump is quite popular and is even used in aquariums. If you need the original from Thetford then – spare part number is 33368. Here is how it looks:

3. The flush button is not working

This is the most uncommon failure you can meet, but it happens sometimes. Don’t forget to verify that the fuse is in good order and the flush water pump is working. Only then this intermediate part is out of order and requires replacement.

Leaking toilet liquid from the bowl into the cassette compartment

All cassette toilets are designed with a tight connection between the bowl and portable black water cassettes. This is usually the case of the most problems with all leaks.

But few drops of flush water can accumulate between the rubber seals when the water is drained and is not a problem. This water is clean and will not damage your caravan or motorhome. Check the gum and grease for tighter contact.

If the water is not a clean one, then it may be harmful and even bring an unpleasant smell over time, so do the following:

Check if it is in the correct position after refitting and if the rubber ring is tight. Plastic grooves for or on the cassette might get worn and check if no foresight objects get under or prevent placing a cassette in the right position.

Check the integrity of the cassette tank rubber packing itself. If displaced – then it will be an easy solution, but if the lip seal is damaged, then order a replacement.

Flush water continues to run after flush

This problem is mainly common for Dometic toilets and is often caused by cheaper or less reliable parts used by manufacturer and offer better pricing on the market.

After filling the flush-water tank to maximum and then flushing the toilet with a flush water pump the water continues to constantly run into the bowl. It may continue until the flush-water tank is emptied to the level of the flush outlet.

This failure appears when the anti-siphon valve gets stuck, blocked, or is not closing tight. This happens because of muck in it or paper blocks the valve.

In some cases, this can be caused by using too much rinse aid. Try flushing through several tanks of warm water to try to unplug and clear the valve from much or paper.

If this doesn’t help, you might need to remove the anti-siphon valve for manual cleaning or replacement.

No filling level display

The float in the cassette can get stuck or simply get jammed by toilet paper. If you are unsure or expect the toilet to be at a high level, then a visual check is the right way to avoid overfilling, but most sure is to empty the cassette at the first opportunity.

Once emptied – clean float in the cassette and do not use any high-pressure cleaner. Just fill it with clean water and shake well – will release the float.

RV Cassette Toilets
RV Cassette Toilets

How to Service a Dometic and Thetford cassette toilets?