Dometic CTW 4050 toilet pump replacement

Hi Yorkyladandlass

How did you fix problem in the end as mine is doing exactly the same and I just need to know how to access pump to check it out as it might just need the blades turning after lock down - Thanks

Having had to take my Dometic loo out to replace the anti-syphon valve I can confirm that the water inlet plate has to be removed first. This is just four screws but you will need to VERY CAREFULLY cut through the sealant behind the inlet. I did this with snap-off blade craft knife with the blade extended to its longest. I put masking tape around the fitting so that the blade didn't scratch the surrounding paintwork. Once the inlet is removed the loo will lift out easily once the base screws are removed. Beware of  the 12v wiring which needs to be disconnected at the loo and there is also (on mine at least) a small drain pipe going through the floor. 

Replacement is just the reverse of removal but you will need to replace the sealant around the edge of the filler inlet plate. Clean off the old sealant first.

Hope this helps.

Forgot to say in post above, there is a wall plate of sorts and you do have to lift the toilet up by about an inch or so to remove it.

Thanks John, looks like this weekends job I will let you know how i get on, much appreciated :-)

Our Dometic loo pump stopped working and I managed to remove the it once the screws were removed. It was very fiddly, but having removed the toilet I found there was nothing wrong with the pump, it was the flush button that wasn't making contact, sprayed it with cleaner and all appears to be working. 

I learnt quite a bit from dismantling the toilet. First, the pump could be replaced by a much cheaper version than the extortionate price dometic require, second, if the flush push button packs up I will not be paying £124.00 for a replacement PCB and wiring, I will find the two contacts on the PCB and wire it to a door bell from Screwfix which will cost me £3.45 to work the flush.

One wonders why a PCB is even required merely to operate a push button contact.

 Because it lets dometic charge extortionate prices for spare parts to those who arent as tech savvy as others

For the benefit of new readers who have a failed pump I hope the following will maybe save some unnecessary work. This is based on a Dometic CTW4050 toilet in a 2015 Lunar caravan but will apply to similar Dometic units.

If the toilet pump stops working, it may not be the pump itself that has failed. You can check a couple of things before ripping out the toilet (which you really don’t want to do unless you have to)

There are usually 2 fuses; the main one in the caravan fuse panel (10A on my caravan) and a second one underneath the toilet control panel (7.5A). Needless to say the 7.5A one should blow first and of course it’s the least accessible.

To get to this fuse you have to remove the control panel (orientations are given looking at the toilet  with the word Dometic on the control panel being at the top). The control panel is held in place by 2 spring clips (similar to those found on a ceiling spotlight) at top and bottom. To remove the control panel use a couple of small screwdrivers to gently lever up the right hand side of the control panel where it sits in the casing. Once you have prised it up you can remove the control panel, and see the pump contacts and fuse under the panel. Check these are OK, and no obvious damage to the PCB or wiring/connectors. If all is OK, you will probably need to remove the toilet to change the pump – see previous posts - but just make sure you are getting 24V to the panel with a voltmeter.

If the fuse has blown the cause might be sediment in the bottom of the flush tank, especially if you use a pink flush additive. Dometic have not fitted a drain tap to the flush tank (!) so it is impossible to drain it completely either for winterisation or for cleaning. Dometic advised that best way to flush it is to pour warm water in to the flush tank and then pump it through at least 5 times. I didn’t want to stress the built-in pump any more by flushing the sediment though it so I bought a drill-driven pump from Halfords (https://www.halfords.com/tools/power-tools-and-accessories/power-tool-accessories/laser-drill-pump-221959.html) and sucked the tank up through the filling line with a bit of garden hose, which worked a treat. Something I will add to my winterisation routine.

I will have a look at the caravan wiring diagram and if the toilet circuit does not feed anything else I may swap the fuses round so that the 7.5A fuse is in the main fuse panel.

My pump has stopped working on the Dometic CTW 4050 toilet. We have a Lunar Clubman 2014 caravan. 

Thanks to, JohnM20, for a very good, step bystep guide, on how to remove and fix the problem.

I will have a go at fixing it sometime but for now, I think I may just use a sturdy two litre empty bottle, that I can refill and just stand next to the toilet.

I would just add. If you take the cassette out of it's housing and the top, left hand red light comes on. Well, is this not a sign that the pcb is operating normally and you do not need to remove the wall,(as it is called in the instructions book), to check the 7.5 fuse is working. Is this correct ?

Finally, a question to member, Marybeth, who posted a very good bit of a advice on how to help clear the gunge that builds up in the flushing tank. You mentioned, "make sure you are getting 24v feed to the panel". I am a bit ignorant here. I thought the caravan worked on a 12v system. What am I missing ?

Thank's for the advice. Will post when I find time to fix the problem, with the pump.

The pump not working on our Dometic 4050 was just the final straw in a long list of things that went wrong with it within 5 months of getting the van - which is why we now have a Thetford.  Touch wood - it's been trouble free for the last eighteen months.  Best decision I have made in a long time - an absolutely useless piece of kit.