This topic will deal with replacing a Thetford toilet water pump in this case a model C402C in other models the components will be similar but may be located in different places, all will require a switch, pump, holding tank and will be protected somewhere with a fuse.

If you need this topic you are no doubt having problems with your flush and one of the first ports of call is the fuse, having said that fuses rarely go wrong (burn out) unless there is a good reason for it.
If your fuse is blown you could replace it [b]with one the same size[/b] which may cure the problem but will more likely not.
In my case it meant I could hear the pump trying to work but no flush water, so I suspected a siezed impeller.

The fuse is located in the cassette compartment on the left side on my model.


The model number was found just inside the cassette door (handy for finding downloads or contacting Thetford about spares)


NOTE just read this back and need to add a safety note here............NEVER work on live equipment specially when it involves water. Disconnect any hookups and the battery before starting to dismantle.

My loo is the Thetford C402C which looks like this


and the area marked in red is where you get access to the pump.

The handle that opens the flap is on a splined shaft and just lifts off, next comes the control cover


This needs careful prizing off at the front and back as you will see when I turn it over


As you can see parts 1 and 2 in RED are the pins that hold it in place.

1 and 2 in BLUE are where I unplugged the electrics.


Under that is a large plastic cup which needs removing too (I had to gently lift it with pliers as its a tight fit)
see image


In the image above No 1 arrowed is the flush pipe after removal from the pump (tucked in there so I don't lose the end)
No 2 arrowed is a rubber ring that seals the cup when fitted in the tank (it goes where the pink dashes are) Try not to damage it or lose it in the tank or you will need new one.
No 3 arrowed is a rubber grommet that seals the cable in the base of the cup.

Getting the pump out of the tank was something of a struggle as the gap it fits in is quite tight and the flush pipe attached is a sturdy bit of kit that doesn't bend easily pulling on the electric cable though not recommended was the only way to raise it from the lower reaches of the tank (and it had to come out or the flush would never work again)

A short pause here to ponder on the production of black stuff in flush water ...........I have no idea why this happens and can only speculate that it is
1 some sort of bacteria that grow in the water or.....
2 the pink stuff somehow coagulates in the tank or
3 something else is happening that I am not aware of?

Anyway I read of others having this problem and the inside of my tank on opening was coated with black crap of some sort.

Sharp eyed members will have seen it on the pump pipe in the image above (which is a cream colour)

Also on the pump (I cleaned it a bit before I shot this)



No prizes fo guessing what is jamming the impeller
Once out I did manage to get the impeller to turn a bit but it was very tight ............so a new pump is needed.

After finding the part number I tracked down a supplier leisureshopdirect.com sell genuine parts and that will do for me (there are lots out there for sale some 1\2 that price but not necessary made by Thetford) its your choice

http://www.leisureshopdirect.com/caravan/water/product_29418/water_pump_12v_for_thetford_cassette_toilets.aspx

So then I had to order a new pump ..............then I have to cut and join the new wires to the control panel and refit the pump

After trying hard to flush all the crap out of the tank (that opening and the sight glass seem to be the only ways in and out

An alternative to replacing the pump on youtube and although it didn't work for me might help someone else

https://www.youtube.com/watch?v=ItDVpmR1L4s

part 2 fitting the new pump to follow

..............................................................................................................................

Well the postie delivered my new pump, So what's in the bag?

A new pump
a plastic bit to secure it (not needed on my model)
instructions (not for my model)
and some shrink wrap


the first step is to cut the old pump off the cable

and throw it in the bin.
Next strip the remaining wire ready for the new join

Before you crimp the new wire to the old DO NOT forget to put the shrink wrap on the cable


Join blue wire to blue wire and brown wire to brown wire

Next you need a heat source .........I used one of these, DIY stores sell them for stripping paint


And something to protect the loo from the heat, I used some hardboard and a piece of alloy to shield the plastic toilet from the heat


You need to apply enough heat to shrink the sleeve enough to provide a watertight seal
The next image shows
1 the cup seal in place
2 the grommet over the cable in place (you may need a screw driver to fit it correctly)
3 the flush pipe reconnected


Re connect the cables to the switch circuit board

Next comes the hard part......you now need to wrestle the pump with flush pipe attached into the small aperture in front of the switch housing
..................not easy but it can be done.

Once the pump is in position replace the cup and connect some power...............either battery or mains
(in my case mains.............no battery)

Add water to the flush tank and press the flush button...............if it works you have done a good job refit the control panel and the flap handle ............open the flap to allow the test water into the cassette.

Well that's how its done

One last tip ...............it's a little known fact but if you lift the covers in the cassette compartment there is room to store 4 bottles of chemicals inside them.