Cassette in Jayco silverline swollen, this is the second one we have had
pugdog said
03:30 PM Jan 26, 2022
Hi there fellow grey nomads. Took advice years ago with our Jayco sterling using nappy san or equivelant with eucalyptus oil and was fine. Did the same in our Jayco silverline and the first cassette was swelling and hard to put back, Thetford changed it, now the this one is doing the same. Phone Thetford and when I said what I have been using, he said thats your problem, only use approved Thetford products ie KemClean. I said but it always smelt and it was fine using nappy san or equivelant in the sterling. I said hundreds on the forum say they use it and have no problems. He said we have a new product with eucalyptus.
He said I have never come across this that the cassette has expanded except yours and the guy in the caravan spare said the same
we went to the caravan place and bought the Kem Clean concentrated with eucalyptus and will see how that goes. If the cassette expands more we will have to replace it.
what do others think???
Possum3 said
05:20 PM Jan 26, 2022
Welcome to GN's pugdog.
It would be my belief that the Cassette is building up too much 'Gas" because it is getting hot, not from the sodium percarbonate solution, if the cassette is sealed tightly, it will expand.
Jim Donney said
05:29 PM Jan 26, 2022
I recently installed the SOG system on my Dometic cassette because during the warmer months it was almost impossible to minimise the smell by using the recommended tables/liquid. The SOG system is brilliant and only takes an good two to install.
pugdog said
05:52 PM Jan 26, 2022
Hi there, thanks for reply. When you are saying ?gas? do you mean using cassette for other than wee, we only have used ours in all vans for wee.
pugdog said
05:54 PM Jan 26, 2022
Hi thanks for reply, dont know what you mean by SOG system?
It is a ventilation system that eliminates the need for any chemicals in the toilet cassette. It took an hour or two to install.
Ivan 01 said
09:48 PM Jan 26, 2022
pugdog wrote:
Hi there fellow grey nomads. Took advice years ago with our Jayco sterling using nappy san or equivelant with eucalyptus oil and was fine. Did the same in our Jayco silverline and the first cassette was swelling and hard to put back, Thetford changed it, now the this one is doing the same. Phone Thetford and when I said what I have been using, he said thats your problem, only use approved Thetford products ie KemClean. I said but it always smelt and it was fine using nappy san or equivelant in the sterling. I said hundreds on the forum say they use it and have no problems. He said we have a new product with eucalyptus.
He said I have never come across this that the cassette has expanded except yours and the guy in the caravan spare said the same
we went to the caravan place and bought the Kem Clean concentrated with eucalyptus and will see how that goes. If the cassette expands more we will have to replace it.
what do others think???
Many of the cassettes have a relief valve which should vent to the outside.
If it is blocked it may pressurise the tank and it will try to vent through the lid and smell in the van.
Thanks for the reply, will look into it. Cheers pugdog
KFT said
05:44 PM Jan 27, 2022
Ivan 01 wrote:
pugdog wrote:
Hi there fellow grey nomads. Took advice years ago with our Jayco sterling using nappy san or equivelant with eucalyptus oil and was fine. Did the same in our Jayco silverline and the first cassette was swelling and hard to put back, Thetford changed it, now the this one is doing the same. Phone Thetford and when I said what I have been using, he said thats your problem, only use approved Thetford products ie KemClean. I said but it always smelt and it was fine using nappy san or equivelant in the sterling. I said hundreds on the forum say they use it and have no problems. He said we have a new product with eucalyptus.
He said I have never come across this that the cassette has expanded except yours and the guy in the caravan spare said the same
we went to the caravan place and bought the Kem Clean concentrated with eucalyptus and will see how that goes. If the cassette expands more we will have to replace it.
what do others think???
Many of the cassettes have a relief valve which should vent to the outside.
If it is blocked it may pressurise the tank and it will try to vent through the lid and smell in the van.
A blocked vent was what caused ours to do that too. Pulled it apart and cleaned and no problem since. The nappy soaker will create heat if you use too much. we only drop a spoonful on top of a number 2 and have no issues at all.
Doing this over more than 10 years now.
Frank
pugdog said
12:05 PM Jan 28, 2022
Hi KFT, thanks for that, so you use nappy san. We dont use ours for no. 2 only wee. So I guess the nappy san is causing cassette to swell. Anyway have stocked up on Thetford Kem Clean Blue concentrate with eucalyptus now and will only use that. At the moment will leave it and if cassette gets to hard to take out and put back will have to replace it and do what Thetford said just use approved Thetford products. Happy travels. pugdog
Peter_n_Margaret said
04:05 PM Jan 28, 2022
Nappy san does NOT produce gas.
Cheers,
Peter
pugdog said
04:32 PM Jan 28, 2022
Hi Peter, It is a mystery then, no explanation. According to Thetford it is non approved, so will play it safe. If we buy another will only use their products and if it happens we will have come back. As I said we only use I for wee.
Thanks for that.
Cheers
pugdog (Dolores)
Ivan 01 said
06:31 PM Jan 28, 2022
Hi Delores
Easily proven.
1 Take a one or two litre plastic milk container and put in a spoon full of Napisan and a cup of hot water, fit the lid and shake. Just beware it may blow the lid off.
2 Take a 20 litre home brew plastic barrel and put in a couple of spoonfuls of napisan and a litre is so of hot water and shake. Watch what comes from the small hole in the lid but keep your face clear of the hole.
When Sodium percarbonate begins its chemical action of actually cleaning to create a sanitised surface it foams as it releases oxygen.
Oxygen is what sanitises the canister or in the washing soaker helps to break up a stain and sanitise the washing.
Sodium Percarbonate or Napisan is marginally less effective the colder it is used. Hot works extremely well.
As you travel the sodium percarbonate gets shaken around and if that vent we talked about above is not working as it should then the pressure that is created causes the canister to blow out or expand. That is why Thetford wont cover warranty if using Napisan or derivatives. The Blue sanitiser for normal use and the Green for disposal into sensitive septic systems.
Save the bother and use the recommended Thetford products.
Hi there fellow grey nomads. Took advice years ago with our Jayco sterling using nappy san or equivelant with eucalyptus oil and was fine. Did the same in our Jayco silverline and the first cassette was swelling and hard to put back, Thetford changed it, now the this one is doing the same. Phone Thetford and when I said what I have been using, he said thats your problem, only use approved Thetford products ie KemClean. I said but it always smelt and it was fine using nappy san or equivelant in the sterling. I said hundreds on the forum say they use it and have no problems. He said we have a new product with eucalyptus.
He said I have never come across this that the cassette has expanded except yours and the guy in the caravan spare said the same
we went to the caravan place and bought the Kem Clean concentrated with eucalyptus and will see how that goes. If the cassette expands more we will have to replace it.
what do others think???

It would be my belief that the Cassette is building up too much 'Gas" because it is getting hot, not from the sodium percarbonate solution, if the cassette is sealed tightly, it will expand.
Hi there, thanks for reply. When you are saying ?gas? do you mean using cassette for other than wee, we only have used ours in all vans for wee.
Hi thanks for reply, dont know what you mean by SOG system?
It is a ventilation system that eliminates the need for any chemicals in the toilet cassette. It took an hour or two to install.
Many of the cassettes have a relief valve which should vent to the outside.
If it is blocked it may pressurise the tank and it will try to vent through the lid and smell in the van.
Here is a list of parts that may help.
https://www.caravansplus.com.au/spare-parts-diagram-thetford-c200-cassette-toilet-holding-tank-p-11808.html
Thanks will look it up. Cheers pugdog
Thanks for the reply, will look into it. Cheers pugdog
A blocked vent was what caused ours to do that too. Pulled it apart and cleaned and no problem since. The nappy soaker will create heat if you use too much. we only drop a spoonful on top of a number 2 and have no issues at all.
Doing this over more than 10 years now.
Frank
Hi KFT, thanks for that, so you use nappy san. We dont use ours for no. 2 only wee. So I guess the nappy san is causing cassette to swell. Anyway have stocked up on Thetford Kem Clean Blue concentrate with eucalyptus now and will only use that. At the moment will leave it and if cassette gets to hard to take out and put back will have to replace it and do what Thetford said just use approved Thetford products. Happy travels. pugdog
Cheers,
Peter
Hi Peter, It is a mystery then, no explanation. According to Thetford it is non approved, so will play it safe. If we buy another will only use their products and if it happens we will have come back. As I said we only use I for wee.
Thanks for that.
Cheers
pugdog (Dolores)
Hi Delores
Easily proven.
1 Take a one or two litre plastic milk container and put in a spoon full of Napisan and a cup of hot water, fit the lid and shake.
Just beware it may blow the lid off.
2 Take a 20 litre home brew plastic barrel and put in a couple of spoonfuls of napisan and a litre is so of hot water and shake.
Watch what comes from the small hole in the lid but keep your face clear of the hole.
When Sodium percarbonate begins its chemical action of actually cleaning to create a sanitised surface it foams as it releases oxygen.
Oxygen is what sanitises the canister or in the washing soaker helps to break up a stain and sanitise the washing.
Sodium Percarbonate or Napisan is marginally less effective the colder it is used. Hot works extremely well.
As you travel the sodium percarbonate gets shaken around and if that vent we talked about above is not working as it should then the pressure that is created causes the canister to blow out or expand.
That is why Thetford wont cover warranty if using Napisan or derivatives.
The Blue sanitiser for normal use and the Green for disposal into sensitive septic systems.
Save the bother and use the recommended Thetford products.
Yes have bought another bottle of Kem clean.