Contents:

1.  Modification to Thetford Toilet C4 2. Not Flushing

     Our previous Motorhome had a Thetford bench toilet.  Press the hand pad and the flush water swirled around the bowl in a reasonably efficient fashion.  Easy, checking the handbook I found this is called the C2 Type.

     When we changed our Motorhome for the Autohomes Wanderer we were surprised to find we had to press the hand pad in a clockwise direction to operate the bench toilet. This I found was designated the C4 type.  This was obviously produced for those “Wild Campers” who don’t have a leisure battery, but we have one!

     After a weekend away to assess the van, before our booked month in Spain. It was obvious that our old hands, we have just retired, could not press hard enough to obtain a complete swirl around the bowl to allow the chemicals to clean efficiently.  The Grandchildren could not get the “Hang” of things either. It was proving too problematic.

     I made some telephone calls and found that modifications parts are not available. I had considered modifying up to a C2 type of toilet. This meant changing to a C2 type.  The price of this change certainly inspired some thought to a possible modification for an electrical pump operation.

     Perusing the Thetford site on the Internet, www.thetford-europe.com, where a handbook can be downloaded, titled; “thethetfordtoiletparts.pdf”  This made it obvious how the whole thing worked and how a possible modification could be arranged.  The C3 Type was an inspiration.

     This modification had to be a “reversal,” as all changes and modifications in a Motorhome should be.  The future purchaser probably might not like the modification. The other consideration, would the modification prove reliable over the long term? 

     With this in mind I produced my electrically operated C4 toilet. 

     The “Mod” is basically cutting the pipe which produces the flow to the toilet rim and placing an 12Volt pump in the cut position.  This would allow the push bellows operation and the electric operation.

     One concern we have learned to live with is that on the C2, it has a protected operation, the pump will not work if the cassette is removed during cleaning.  My modification does not have this built in and will operate with the cassette removed.  This modification will be added later, but for the present a notice on the push button will suffice. [ The Grandchildren have been given a verbal instruction.] The modification proposed would comprise of a lever micro switch in series with the press button. Constructed close to the cassette. So when the cassette is removed the lever micro switch would go open circuit, holding off the press button.

     Before work was carried out I ensured parts were available in case I had to reverse my “Mod.”  To be sure I purchased from my local caravan dealer the parts I would “Destroy.”  The part is the “Flush Tube” and has the part number: 20292, which comprises the Flush Tube, Seal/plunger/spring, O-ring, and Nozzle.

     Other parts need were sourced from a local DIY store.  They are: 

     1. A “Y” piece with outside diameter of 19mm, suitable for the Flush Tube.  This has an inside diameter of 16mm.

     2. A length of clear plastic tubing with 12mm outside diameter and inside diameter of 9mm.

     3. A length of plastic tubing with 15mm outside diameter and inside diameter of 12mm. [I was able to use garden tubing for this.]

     4.  A 12volt immersible pump.

     5. A Push switch.

     6. A suitable length of 2 way Cable.

     The pump came from one of the Motorhome Shows, it was blue in colour and cost £10. It was quite small and was very suitable for this modification.

      The identification markings  on it are;

"BOHLER PUMP -TAUCHPUMPE MODEL T3 12V DC 81 Min 0.6bar."

     The dealer I purchased it from advertises in the “MMM” magazine.

     To start the “Mod” requires the bellows Flush Cap to be removed from the bench. This is eased off the retaining rim by pulling gently in easy movements, pulling from one side to another.

     When removed the Flush Tube can be seen attached to the bellows at it’s base.

 

     The Flush Tube is then cut approximately one third the length from the bellows side. Remove the assembly and take it to a convenient place of work.

     The completed work can be seen here.

     A “Y” piece was fitted in the flexable tube by cutting  a gap.  This “Y” piece was obtained from a local DIY store and was found in the Garden Accessories Department where parts were being sold for the garden ponds and fountains.  This white coloured “Y” piece has 19mm outside diameter and a 16mm inside diameter which fits the Flush Tube ideally.

     The arrangement of fitting the tubes to the pump and “Y” piece might seem a “Hotch Potch” but the Mark 1 modification had a single plastic pipe which I heat 'melted on.'The pipe developed a kink and reduced the flow. So the final arrangement has produced a rigidity required.  This was to fit the 15mm outside diameter pipe inside the "Y" piece, then the clear tubing with outside diameter 12mm,  inside the 15mm pipe, then the other end on to the pump which had an outside diameter of 9mm  which was the size of the clear tubing.

     The pipes were secured with Solvent Cement.  It is not important to worry about leaks as as any water leakages return to tank. The Solvent is there to hold the pipes when under flush pressure.  The result can be seen below:

     The photo below   illustrates the modification ready for fitting inside the bench.  The pump is secured to the Non Return valve with cable ties. This ensures the assembly will fit neatly inside the baffle plates located inside the bench.

     The 12 volt feed cable is fed through a grommet which is conveniently located on the right wall of the bench.  This grommet is quite small and a tight fit, but with patience it can be used.  The cable is then brought out to a switch which I fitted on the lower wall, as I felt if the modification had to be removed this hole could easily be camouflaged.  Images below show the Push Button fitted.

     The cable from the button was then fed to the fuse panel, making sure the source was fused.

This modification has proved to be very reliable in service, with no problems experience through out our tour of Europe during the summer of 2003 and is still in use Sept 2011.

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For those who might be getting their Motorhome out of storage, as we are, you may find that the Thetford Toilet gives trouble. Intermittent or not flushing. 

Turn off the toilet 12 Volt electrics before carrying out any repairs. Check the fuse.

The solution is to remove the toilet holder in the toilet body, This container is a push fit and can be removed by easing the rim by small amounts around it's perimeter.  This then exposes the inside of the Thetford bench and the water immersed pump. 

Remove the pump and check for any dirt obstacles at the bottom of the pump, which might have stopped the pump impellers.  Rotate the the impellers by hand to ensure they are free. They can be found at the inside base of the pump body.

Turn on the electrics and start the flush while holding the pump in your hand.  It's OK to do this for short bursts, but not recommended for long periods without it being immersed in water.  The water keeps it lubricated. 

If after this the pump does not rotate, check the cables back to the fuse.  Check the fuse and ensure you have 12Volts at this point.  If you have, then you must consider the pump as being faulty.

Notes: 

Cassette C2 

Type:  Permanent, fixed bowl toilet for caravans and Motorhomes.  This Cassette toilet has an integrated freshwater tank and features a powerful touch button electric flush.

Cassette C4

Type:  Permanent, fixed bowl toilet for caravans and Motorhomes.  This Cassette toilet has an integrated freshwater tank and features a hand operated flush.

On both types the cassette waste tank has a greater capacity than the fresh tank.  The theory is when the fresh tank runs out it is time to change the waste tank.

Information on the Thetford Toilet can be found at their web site.  Where also can be found spare part drawings and numbers.  Making it easier to order the parts:
www.thetford-europe.com/

The link below will take you to Hints and Tips on Cassette toilets. It will also give you the opportunity to download a owners hand book.
http://www.thetford.nl/the/thomecon.nsf/web/cleaning_waste_tank_en

Here it is possible to renovate your toilet:
http://www.thetford-europe.com/en/about-thetford/news/2011/thetford-launches-toilet-fresh-up-set-for-c400-cassette-toilet.aspx

Features: 

Finish: white 
Flush: electric (12V) on the C2
Manual:  on the C4
Integrated pour-out-spout: yes 
Separate toilet tissue storage compartment: yes 
Waste tank capacity: 20L 
Freshwater tank capacity: 15L