# Thetford C250 venting



## Pugwash (Jun 12, 2005)

Hi, 

We have one of the new Thetford C250 toilets in our six month old motorhome. I'm aware that many people are having problems with this flimsy design but I haven't seen any mention of our particular issue and wonder if anyone can help. From the day we picked the van up (brand new) we've been able to smell this toilet when we're driving. I've taken it back to be looked at and everything checks out OK and I'm now questioning it's installation. I should also say that we had a SOG fitted when new before we ever used the vehicle so we don't have experience of this toilet without a SOG. However, our previous van also had a SOG (with a C200 - not a C250) and it was perfect. Never had a whiff of anything, ever. 

My question about the installation is this: Should the chamber into which the cassette slides (ie the toilet base unit) be sealed from the interior of the vehicle? In my case it certainly isn't as a number of pipes (including a large heating pipe) and wires travel through the corner of this chamber into the cupboard beneath the wash basin. Air from the chamber can easily transfer to the cupboard which is not sealed from the interior. 
Also, should this chamber be vented to the outside somewhere? Again, in our van it isn't. Any air venting from the cassette through the pressure/vacuum valve will do so into the chamber surrounding the cassette and from there into the bathroom cupboard then through to the bathroom. And so to the rest of the vehicle interior. 

Is this the correct way to install this toilet? It doesn't seem to make sense to me. I would have thought that foul air getting into the interior was inevitable with this set up. The van is a 2010 model and built by a leading manufacturer - I would have thought they would know how to install the toilet. 

Can anyone advise?
Pugwash


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## trek (May 1, 2005)

when the cassette is fitted into the base unit it opens a float value on the top of the cassette for pressure equilisation

this value has a float valve & this is supposed to close if fluid sloshes around and lifts it when driving. This is located underneath a cover approx 3"x1" on the top of the cassette near the handle.


my guess is that when driving air is being admitted in via the sog outlet through the sog piping and into the cassette - then it is leaving the cassette loaded with fragrances via this cassette air vent & into the interior of the toilet unit & hence the van


Now this has all been designed to accept Thetfords own Sog equivalent air vent . where the fan & charcol filter fits into the base of the toilet unit , so that when the Thetford fan if fitted operates it draws the air down through a pipe in the centre of the cassette & out through the floor vent

what I suggest you do is try driving without the sog pipe connected to the cassette & use the sog pipe blanking cover instead.


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## Pugwash (Jun 12, 2005)

Hi Trek. 

I think you're on the mark there. I was speculating on something similar but thought the vent which opens when the cassette is installed was allowing air to "drift" back into the toilet chamber. Its quite possible that when the vehicle is moving air is being gently pushed backwards through the SOG and through the cassette. I also thought that the removable base plate which the bottom of this vent sits on, should have a vent to the outside. I didn't know about the Thetford SOG-equivalent which fits in there. This explains it s purpose and why at present its blanked off.

I'll try your suggestion and see if blanking off the SOG prevents this "backflow" when driving.

Thank you for your help.
Cheers,
Pugwash.


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## CliveMott (Mar 10, 2008)

The underseat components should be sealed from the inside of the van. If yours are not I suggest you take it back and get it done properly. Unfortunately many UK converters don,t install fridges properly either as the back of these should also be sealed from the inside of the van. Many times they are not and this could be where fumes expelled outside blow back into the van.

C.


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## Pugwash (Jun 12, 2005)

Hi Clive and Trek,

It certainly makes sense that the toilet base chamber should be sealed from the interior of the vehicle. That mine is not is a design issue rather than a production line error. The 3" air heating pipe that passes diagonally through the bottom corner of the toilet base chamber on it's way through to the cupboard leaves a hole around it's circumference that has no propsect of ever sealing, short of using some expanding foam. (The cupboard hole is double skinned and angular ona corner - the pipe is round). In the end I may have to use foam but it's a one-way trip with that stuff and I see it as a last resort. I may be able to wedge some foam down there. Still thinking about that one.

The other idea I've come up with is in response to Treks comments. On the base of the chamber, where the cassette slides, is the plastic plate which the vent tube sits on. This has a raised "bar" and as the cassette slides in the raised bar lifts the vent release in the cassette, opening the vent which then vents into the base chamber. As I have a SOG fitted do I still need this vent to be open? Surely the SOG pipe will allow any presuure equalisation required by temperature chnages, atmospherics etc to take place? If I remove this 5" by 3" plate then the cassette vent will not open when I slide the cassette into place. If I'm right about this the only vent remaining will then be the SOG pipe which goes to the outside. Does it make sense to remove this plate to prevent the internal vent opening?

Unless someone tells me I've missed something I think I'll seal the gap going through to the cupboard and remove the plate so the Thetford vent remains closed, then give it a try.

Thanks to you both for your helpful replies.
Regards
Pugwash


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## trek (May 1, 2005)

Hi Pugwash

sounds to me like you've sussed it . thats a good idea to remove the Thetford Charcol / Fan cover from the base this will keep the cassette float closed. will be ok as it will vent via sog outlet

(I have fitted the Thetford vent on my own van)

Note my Thetford toilet installation is not sealed to the walls or floor & I wouldn't have expected it to have been

I too have services running behind the unit


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## Pugwash (Jun 12, 2005)

Hi Guys,

With your help I think this is now fixed.

Although I fitted the SOG on my previous van this one was fitted by the dealer. I just had a look at the fitting instructions on the SOG website and guess what? It says to remove the cover plate in the base so the internal cassette valve remains closed when the cassette is in place! This is the conclusion just reached in this thread. The installer of this SOG obviously didn't read the instructions properly. It's caused us considerbale inconvenience as the toilet has been virtually unusable.

I'll try it with the plate removed so the vent is closed before I go jamming all kinds of things in the hole to seal the toilet base from the cupboard. I can see that without the SOG the base should be sealed as the internal Thetford vent allows foul air into the base unit, but with the SOG it should vent to the outside even without the fan running as that's the only escape for air.

Incidentally, this expalins why we immeidately noticed this SOG wasn't as good as the previous one when the toilet was in use. It's because much of the air it was drawing into the cassette was being drawn in through the internal vent and not through the toilet bowl. It all makes sense now!

Thanks again to you both for your helpful input.

Regards
Pugwash.


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## erneboy (Feb 8, 2007)

Our is a C250. I fitted my own sog and removed the plate from below as per the instructions. It works well although I am not at all impressed with the way the C250 is made, cheap, flimsy, difficult to clean and does not flush at all well. I mentioned all this to the dealer when the van was new, might as well have talked to the wall.

Just check that your sog fan is not wired the wrong way round, if it was pushing air in rather than out it would stink, Alan.


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## Pugwash (Jun 12, 2005)

Hi Ernieboy,

I agree that the C250 does feel as sturdy as the previous C200 and doesn't seem as well engineered.

Thanks for your suggestion regarding the incorrect wiring. One of my first thoughts after we picked up the van was that the SOG was blowing instead of sucking but this proved not to be the case. I think I've now got to the cause of all this trouble with the vent issue. We'll soon know on our next trip!

Thanks for you help,
Regards
Pugwash.


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## erneboy (Feb 8, 2007)

It might be worth telling you that our in our van the compartment the cassette fits into is by no means sealed from the rest of the van, many other services run through it, also it is not vented. Even so we don't have smells, Alan.


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## Pugwash (Jun 12, 2005)

Thanks Erneboy. I've removed the plastic plate from under the cassette so the Thetford vent will no longer open. Hopefully that's fixed it. We'll soon know!

Thanks also for the info about the compartment in your van not being sealed.

Regards
Pugwash.


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