Chrill Posted June 9, 2016 Share Posted June 9, 2016 Hi Everyone I've just purchased a second cassette for my Thetford loo and it came as part of a 'refresher pack'. Basically new cassette, toilet seat and some chemicals. However the automatic pressure relief valve on the new cassette is different to the valve on the original, and the new cassette clucks into place easily enough but gets jammed when I try to remove it. I can't see any difference in size/shape between the two cassettes, and have tried swapping the valves. Has anyone else experienced anything similar? Thanks :-S Link to comment Share on other sites More sharing options...
PJay Posted June 9, 2016 Share Posted June 9, 2016 I have seen these for sale. Do they come in different models? Maybe you have the wrong model. How old is your van? I noticed that the later ones have wheels, but ours does not. We keep the mechanism well greased with the Thetford spray, and ours still works well after 10 years PJay Link to comment Share on other sites More sharing options...
Chrill Posted June 9, 2016 Author Share Posted June 9, 2016 Thanks PJay Yes, the cassette model is correct (C200), unless there are variations of the C200 cassette? But I don't think so. We have an 09 van and it takes the cassettes without wheels. I'm most confused about the different vents though... I've contacted the supplier for more info. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted June 10, 2016 Share Posted June 10, 2016 When Thetford introduced the C200 range of toilets the automatic vent valve used with a C200 cassette was carried over from the C2/C3/C4 range of bench-style toilets. The design of that valve is shown in the 1st attached photo and in this Thetford video-clip However, there is another design of vent valve available for the C200 range as shown in the 2nd attached photo. The latter valve is used when a Thetford ‘outside vent’ kit is to be fitted to the cassette http://www.jacksonsleisure.com/caravan-and-camping/toilets/cassette-toilets/thetford-outside-vent-for-c200-cassette-toilets/ and it will be seen from the advert that - besides the redesigned vent valve and vent tube - a modified part needs to be installed in the cassette locker. If Chrill’s new "Fresh Up" cassette has the ‘outside vent’ version of the vent valve, the cassette won’t fit properly in an unmodified cassette locker. Link to comment Share on other sites More sharing options...
StuartO Posted June 10, 2016 Share Posted June 10, 2016 On my C200, the cassette goes in without the vent coming into contact with anything, so unless there are radically different compartment designs, I doubt that a different valve would contribute to jamming. Link to comment Share on other sites More sharing options...
Chrill Posted June 10, 2016 Author Share Posted June 10, 2016 Thanks Derek That clears up my confusion on the difference in vents. The original cassette has the outside vent modification (although not actually needed) and the new cassette has the original vent style. So same cassette, different vents which reassures me I've bought the correct cassette at least. Link to comment Share on other sites More sharing options...
Chrill Posted June 10, 2016 Author Share Posted June 10, 2016 StuartO - 2016-06-10 7:57 AM On my C200, the cassette goes in without the vent coming into contact with anything, so unless there are radically different compartment designs, I doubt that a different valve would contribute to jamming. Yes, I now understand the different vents shouldn't affect fit on my van so there's something else going on. Link to comment Share on other sites More sharing options...
PJay Posted June 10, 2016 Share Posted June 10, 2016 How about taking van and new cassette back to the supplier, that may be able to help you . Why did you replace it? If it was a problem , then maybe a new one is not the answer. Hope you get it sorted. Difficult for online help really, need to see whats happening PJay Link to comment Share on other sites More sharing options...
lennyhb Posted June 10, 2016 Share Posted June 10, 2016 Have you got the mechanism set correctly of left hand or right hand installation? Link to comment Share on other sites More sharing options...
Derek Uzzell Posted June 10, 2016 Share Posted June 10, 2016 Chrill - 2016-06-10 9:06 AM StuartO - 2016-06-10 7:57 AM On my C200, the cassette goes in without the vent coming into contact with anything, so unless there are radically different compartment designs, I doubt that a different valve would contribute to jamming. Yes, I now understand the different vents shouldn't affect fit on my van so there's something else going on. When a Thetford C200 cassette is inserted in the cassette-locker a ‘protrusion' in the locker’s roof pushes the top of the automatic vent-valve downwards, opening an air passage between the cassete’s interior and the locker’s interior. When the top of the vent-valve is in the depressed position air is able to pass from the cassette’s interior to the locker’s interior (and vice versa) thus minimising the chances of a pressure build-up (or a vacuum) forming within the cassette. (The fact that air can move from inside the cassette into the locker is why it’s essential that the cassette-locker is sealed from the leisure-vehicle’s living area.) When the cassette is removed from the locker the top of the vent-valve is no longer depressed and the valve seals itself. (If this sealing did not take place carrying the cassette to an emptying point would be extremely perilous!) Thetford’s ‘outside vent’ system comprises a vent-hose, a special vent-valve to which the vent-hose is connected and a replacement ‘protrusion’ that must be fitted into the cassette-locker’s roof. As Thetford’s C200 ‘outside vent’ system is a relatively rare fitment, it’s to be anticipated that the cassette supplied with the “Fresh Up” kit will come with the commonplace standard vent-valve as shown in the first of the two photos I provided in my last posting. A C200’s vent-valve needs to match the cassette locker. As you have the ‘outside vent’ system that will have the locker ‘protrusion’ modification, you’ll need to replace the standard vent-valve that was fitted to the “Fresh Up” kit’s cassette with the ‘outside vent’ valve. It will be plain from the photos that the top of the one valve is quite different from that of the other, so it’s hardly surprising that you’ve had problems removing the new cassette that has the ‘wrong’ valve. I’m doubtful that one can obtain a "Fresh Up” kit specifically intended for a C200 toilet that has the ‘outside vent’ system, but if you discuss this with your supplier they might be be prepared to swap the valves for you. (Unlike Thetford bench-style toilets C200 models load the cassette from the toilet’s rear, so there’s no need for left or right versions.) Link to comment Share on other sites More sharing options...
StuartO Posted June 10, 2016 Share Posted June 10, 2016 Derek, your capacity and skill in researching and revealing this sort of thing on almost any motorhoming topic never ceases to amaze me! So there are different cassette housing designs, one of which lifts the vent valve while the other one doesn't. This vent valve (of whichever sort) is replaced as part of a SOG aftermarket installation by the green right-angled spout to which the SOG hose attaches, for fume extraction purposes. When I bought a Thetford "refresher kit" as a way of acquiring a second cassette I also bought a spare green SOG spout, to make the two cassettes interchangeable. Somewhere in my garage is an unused vent valve. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted June 10, 2016 Share Posted June 10, 2016 When a SOG kit is fitted to a C200 toilet the automatic vent-valve (AVV) is - as you rightly say - replaced by a right-angled ’spout’ to which the SOG extraction hose is connected. When removing the cassette from the locker the SOG extraction hose is disconnected from the spout and a stopper/bung http://www.campervanstuff.com/shop_stuff/index.php?mod=product&id_prd=1215 is pushed over the spout to prevent the contents of the cassette leaking through the spout while the cassette is being emptied. As well as replacing a C200 cassette’s AVV when installing a SOG kit, the mechanism in the locker’s roof that depresses the AVV also needs to be surgically modified. Modifications (and a replacement vent valve) are needed when Thetford’s own Outside Vent kit is fitted. The procedure involved can be found here http://www.bradtech.ltd.uk/products/Outside-Vent-Kit-for-C200-Toilet-T23786.html Link to comment Share on other sites More sharing options...
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