DIY SOG© - Powered Cassette Toilet Vent

With peoples concerns for the environment when adding toilet chemicals some are opting for home brew (Nappy Soaker or a brew of Ammonia, Borax & Disinfectant) whilst others are choosing to use a device called the SOG from Aussietraveller © that promises to treat your black waste using just fresh air. These approaches are all well and good but I am a sceptic and will continue to use what I know works for me (Aquachem Premium Blue©) but I have decided that powered ventilation to the cassette is a good idea and basically can do no harm only good. This will guarantee that there will NEVER EVER be any toilet odour in your RV en-suite.
I chose to go the DIY path for a couple of reasons, one I can't justify the high price of the commercial unit and two its always better to have done something yourself and have it work better than the store bought.
There are a couple of differences with my approach to this. I decided that the toilet enclosure was basically airtight (or can be made so) and therefore all I needed was to add a 40mm hi-flow computer fan to the door and it would provide negative pressure in the toilet compartment and modified a spare lid to allow the air to escape from the cassette unimpeded by any flexible hose, These fans perform badly when asked to pump air thru a hose less than their diameter so ditching the whole hose concept made sense.
This turned out extra good and there is a good flow down the toilet and out the vent when the slide is opened. I fitted a microswitch on the slide actuator to operate the fan whilst the slide is open and the toilet being used. This should keep any smell outside the van.
This all cost around $45 for the fan, microswitch, vent cover, junction box, filter mat and the spare cassette cap and can be done in an hour or so.

Author's Conclusions after 6 months use
Having done this mod I decided to give a full test without chemical for a few weeks, and yes you can do without it and there will be no smell indoors BUT be aware that the addition of air to a cassette of sewerage WILL NOT treat it and wont make it smell any better when you empty it. Also to really use this system you need to be camped out on your own as there is a fair aroma when the slide is open and someone is using the throne. Also if you are unlucky that aroma will re-enter your home via a downwind window. Yuck!
It would NEVER be an option for me in a caravan park if you want the neighbours to speak with you again. My advice, in the bush sure use the system but in the real world get yourself some Aquachem Premium Blue and turn it off.
Note, when travelling replace the vented cap with the standard unless you want a mess to clean up!

This is how it looks on the outside with the vent $3.95 from BCF© attached with 4 CSK SS screws and sealed on with white silicone. Choose the location for the fan keeping in mind that the filter box will be mounted behind it and you will want the door to close properly. 40mmx20mm computer fan mounted over the 40mm hole drilled thru the door infill panel with a 40mm hole-saw. Fan available from CoolPC © for $10.Feed the wires via the existing wiring tubes back to the terminal strip location. The fan is sealed to the panel with blue acrylic putty and the base of a HPM© junction box (larger size) cut to fit and attached with two screws. Cost $4.90 from Bunnings©. The larger size was chosen to allow for more holes so as not to restrict airflow. The lid of the junction box was drilled out with 5 holes using a hole saw and a piece of activated charcoal from a fish tank mat was cut to size and pressed into the lid before fitting over the fan. $5 from pet shop for enough to last for years of replacements. Fit microswitch SM1039 $3.75 from Jaycar© as shown with two stainless self tappers just long enough to hold the switch to the plastic. Make sure you fit the wires before you mount it to make it easier. Adjust the operation by carefully bending the actuator strip so that the fan operates when the slide is open. Thread the wires back following the hoses and wires back to the terminal strip securing with cable ties.

Connect in series with the supply to the fan utilising one of the unused positions to join in to the fan wiring. The wires and terminal strip then push down behind this panel to keep them out of the way. The next part of this modification making a ventilated cap. Start with a new Thetford© "Dump Cap" $11 at local caravan shop. The stainless steel mesh was acquired from a kitchen icing sugar duster from the $2 shop. Just tap out the mesh around the outside edge with a small screwdriver and a hammer.

If you thought this page was helpful check out my other ideas by pressing the "back" button at the top of the page. Cheers Lawrie

Drill a 40mm hole in the cap using the same hole saw, remove the sealing washer and trim the stainless mesh down to size with kitchen scissors. This will prevent any accidental escape of solids from the cassette when moving and keep out any blowies that might show an interest. Insert the mesh and the washer in the modified cap. Next a blank pipe cap was sanded out slightly to be a snug fit on the dump cap and cut away about 10mm at the top to form the vent as shown, cap is marked Vinidex 65mm DWV PVC $3 from Bunnings©. This was attached with Deal Extreme© two part 302 acrylate glue to the dump cap making sure it is in the UP position when fitted to the cassette. A light sand around the edge of the dump cap will ensure the glue has something to key on to. This addition will ensure that no liquid contents will escape from the vented cap when on the road. Here it is ready to go showing the vent cap fitted to the cassette in the rest position and the original stowed under the cassette handle to use as a chemical measure. Test that you have correct airflow using a cigarette in the bowl and seeing if smoke is drawn into the casettee with the slide retracted and the door to the compartment closed. This will show you that everything is working as it should. Now you're done.

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