Installing a SOG Unit on a Thetford Chemical Toilet


Four years… That’s how long it’s taken me from thinking about installing a SOG unit to actually doing it. Action Man, that’s what they call me. Anyway, I’ve done it now! A brief overview follows of a what a SOG unit is, and why we’ve just fitted one, then there are a couple of videos below showing the unpacked kit and how I installed it on our 2001 Hymer B544.

What’s a SOG?

A SOG unit is a simple concept, genius really. Motorhomes and caravans typically have a Thetford Cassette which holds the contents of the loo, meaning you can use the toilet in your home on wheels. Some folks opt never to use them, preferring to use site facilities, and some folks only use them for holding number 1s (wee), not the dreaded number 2s (poop). We were in the second camp for a while, but long term budget motorhoming didn’t include the funds for campsites, so we used the cassette for everything as we frequently free camped or used aires. As an aside I’m convinced, after leaving our cassette unemptied numerous times for a socially unacceptable number of days, that number 1’s honk far worse than number 2s.

And moving on. Both number 1s and number 2s have the unfortunate characteristic of stinking to high heaven, especially if they’re left for a few days, and even more so if they’re jiggled around in a motorhome in 40 degrees heat in Croatia. **shudder** So someone came up with the idea of some thick blue chemical which you pop into the empty cassette with a bit of water. This helps keep the whiff under control, and also helps break down the poop and loo paper. You don’t **have** to use the blue stuff, we tried various other things over time, but the blue chemicals generally did the job best.

The main downside to the blue stuff is it costs wonga (and it’s dubious how harmful it is to our environment, although I’ve never looked into this so don’t really know). A litre of Aqua Kem Blue is coming in at about £12 on Amazon. The SOG unit aims to avoid the need for any chemicals at all. It does this by using a small fan, typically attached to the cassette door although newer vans seem to vet through the roof. This fan is connected via a hose to somewhere on the cassette. Then, when the blade is opened inside the loo (i.e. when you’re flushing it), the fan starts and draws air from inside the van through the cassette and outside, via a charcoal filter to absorb some of the smell. A SOG unit comes in at about £110 (from or, for example). In our two year tour, the SOG unit would have easily paid for itself, regardless of any other benefits. As we intend more long term touring, and Ju managed to get a brand new kit for £75 from eBay, we’re fitting one on economic grounds, but we expect it to be a sniff-killer too.

Also, as the hose is always connected to the cassette, any ponging gases which build up in the cassette when it’s not being used get forced outside the van, rather than back inside the cassette housing in the van via the excess pressure valve. In theory, the SOG does away with the stink, as long as the filter is replaced once a year (they cost an exorbitant £9.50 BTW; I’ll be searching for an alternative active charcoal filter, maybe something like this). We’ve checked out umpteen threads on forums, and met lots of people who have SOG units, and the outcome seems to be:

  1. Folks who haven’t fitted one claim they’re daft expensive, won’t work and stink out your unfortunate neighbours.
  2. Folks who have fitted one swear by them, and say they do work as long as the filter is changed every 12 months. :-)

Something to be aware of: there are different kits, and different ways of installing them, depending on which Thetford cassette you have. Do your research to make sure you get the right one. Our van has the cassette type on a label inside the cassette housing, and printed on the bottom of the cassette: a Thetford C200. The videos below all refer to the C200 install. Also please note that I AM AN AMATEUR! I’m not a professional installer and although I **think** I’ve installed the kit correctly, I may well be proved wrong. Read the instructions – I read them 3 times and still managed to get it a bit wrong, as the video below shows.

Installation of a SOG Unit with a C200 Cassette

This video shows me installing the SOG unit onto the C200 cassette on our 2001 Hymer B544 motorhome. Apologies for the wind noise, it was, erm, windy. The install took about 2 hours, but would have been a bit faster if (a) I wasn’t filming it and (b) I didn’t cock it up.

The C200 SOG Unit Parts

This video shows the bits and bobs which came as part of the SOG kit. There are PDF brochures and installation instructions also available here (half way down the page). These instructions are a bit different the paper ones which came with the kit; I worked from the paper instructions.

We’ll run the unit for a few months and then give an update on how well it has worked for us.

Cheers, Jason


  1. We started off using the proper chemical stuff (albeit the green rather than the blue), but quite quickly realised it was cheaper and easier to just bung in a capful of laundry liquid. It masked the smell as well as any toilet chemicals, and it meant we had one fewer bottle to carry around with us, as our laundry liquid was multi-purpose. We’ll be interested to hear how you get on with the SOG unit though.

  2. Hi Guys,
    we get our blue stuff from Brownhills, 5 litres for the same price you are paying for 1 litre.
    I now also measure it each time I use it, when we first started I would just pour some in, ended up wasting a lot.

    • Hi Ray, both really good points, our decision wasn’t completely financial, I accidentally lied…

      As per Steve and Kiri’s comment you can also try other things to keep the smell down, washing powder, washing up liquid etc. I suspect our case is more extreme than most. We spent long periods without access to a dump point (Southern Italy in winter, parts of Greece for example). No campsites were open, no public loos, no obvious direct access to sewers. Loo honk ensued. I sometimes wonder if the excess pressure valve on ours was working properly too, as the van frequently whiffed, especially when driving.

      Would the SOG manage any better? Dunno. Another point to consider if you do prefer using the chemicals is the fact you either have to carry a load of bottles on very long trips, or you need to source the stuff locally, which means (a) finding it and (b) probably paying much higher than bulk prices in the UK. Our trips were 11 or 12 months at a time, and we didn’t have masses of storage/weight available.

      The debate rages, like Marmite these SOG units! Ours is on now though and I’m pleased we’ve done it. Probably the main advantage will be emptying as often as I like without the feeling I’m wasting any chemicals (regardless of how cheap they were, I’m uber tight fisted when it’s a choice between that an the office!).

      Cheers, Jay

  3. We had a SOG unit fitted as soon as we bought our MH, nearly 10 years ago. You need to be aware that you can’t just ignore the cassette and leave it for days. It needs to be emptied whenever possible for obvious reasons. Our biggest headache is forgetting to to turn it off when we drive away as the fan then turns off with the cassette still open. The fan only works when the lever of the toilet opens the cassette, so it needs to be left slightly open at most times when parked to draw air over the contents which breaks down the solids and paper. Drive away with it still open in the first couple of days after emptying it and you won’t have a problem, but when the smell builds up, you had better remember to shut it or you will be pulling into the nearest layby and bailing out! We have done this so often that we make a point of emptying it whenever we can.
    It may be a stupid thing to do, but we are all human and sometimes there are so many things to think about when we pack up that this is one that’s overlooked occasionally.

  4. Well I for one think you did a cracking job Jay and this right-up’s inspirational! All the work you put into recording, linking & sharing this deserves some kind of ‘Top Camper Dude’ medal. So we don’t mind if you got the phases wrong, it all works fine in the end, top job. Now my decision’s resting on you (both)…depending on whether you give the SOG a ‘Thumbs UP’ or a ‘Thumbs DOWN’ may seperate me from some of my hard earned wongna, so please give it a good testing for us all & your honest feed-back.

    Baz…[Quote]”you had better remember to shut it or you will be pulling into the nearest layby and bailing out” lol :-) :-) :-)

  5. Hi Jay
    We recently bought a 2001 B694 that came with a SOG fitted to the loo.For 9 years before that we had a 1993 B644 without SOG.
    We’ve just spent 5 weeks in the South of France with temps up approaching the 40s and not so much as a whiff from the loo. I am completely sold on the SOG system and wish I’d fitted one years ago. The smell is a “bit” strong when you empty the cassette. I’m sure you will find it an amazing bit of kit.

    • Thanks Mervyn, looking forward to that first whiff as I empty the thing! I learned quickly to close both my nose and mouth when emptying the cassette into various weird and wonderful contraptions across Europe! :-) Cheers, Jay

  6. Hi guys. We have had a SOG in all our Hymers and my wife would not be without it. True there is a bit of a whiff when you empty the cassette but it only lasts a second until you flush the emptying point. I think you will be well impressed.

    • Thanks Deryck. Just been up to the storage place to, hmmm, have a play with it. Seems to be functioning nicely! I did give the box on the outside a little pat of sympathy though. It’s going to have a hard life that puppy…

  7. We found a second cassette to be extremely handy for long periods in Greece and other areas, even when just wildcamping through UK/Scotland.

    We also had a SOG (it came fitted with our MH) and found it very handy. I believe Scandinavia has a no chemical policy, making it an essential bit of kit for there, but regardless, when emptying into drop toilets etc most chemicals are a no-no.

    Have you also looked into the Aqua Kem Green, which is septic tank safe?

  8. Great job on the SOG video, just hope the guy refurbishing the Thetford toilet dosn’t offer his misses any Vaseline if she’s got chapped lips!!!!

Leave a Reply

Your email address will not be published.