Dometic CTW 4050 toilet pump replacement

Another tale of woe. Whilst away in Cornwall last week our Dometic loo developed a leak whenever it was flushed. Thankfully it was clean water. We temporarily overcame the problem by using a watering can in the caravan to flush the bowl.

Yesterday I took out the toilet (I'm getting to be a dab hand at this) and located the leak. Under the rim of the bowl there is a plastic elbow where the supply pipe joins the flush ring around the rim. This can only be seen with the aid of a mirror. Somehow the elbow had fractured. Don't ask me how as there is no stress on the elbow and no water pressure. This meant a complete dismantling of the toilet to get the flush ring free, the main problem is that the plastic supply pipe, 9mm bore x 15mm od, although probably flexible when originally assembled, has now become quite inflexible. Why such a thick walled pipe has been used is a mystery as there is no pressure in the pipe. 

I've now got to get replacement pipe and elbow although this won't be coming from Dometic even though I can only locate, at present, pipe with a 12mm od. I'm sure this will be more than adequate for the job. I'll let you know when it is all finished and up and running again satisfactorily.

I have a feeling I've seen a video on You Tube about how to fix this - which goes to show how common a problem it must be.  I will refrain from any further comments about this particular piece of kit!

We had numerous problems with a Dometic CTW 4050 too. In the end I replaced it with a Thetford unit. Its not a difficult job and our loo is now trouble free

Which Thetford toilet models did you install, Dave Nicholson and RichardandRos ?

Well, that's it, job done. I found a supplier, ( PVC Tube Online Ltd), of the identical size water hose which, if anyone wants to know is actually10mm bore x 16mm od. They also sell the necessary elbows. The whole job cost me less than a fiver to do. I can't really count my time which, in total was about four hours including taking the loo out in the first place. Far cheaper than getting Dometic to do the job of that I'm certain but I shouldn't have needed to do it.

I would ask, of those who know! When I have removed the Dometic 4050 toilet, as well described by kind members. What will I see when I look to remove and change the pump.

Is it easy to get to the pump, once I have removed the whole toilet and taken it out of the caravan, to work on?

I changed a pump, many years ago, on a Thetford and it was as easy as changing a light bulb.

Thankyou, for any helpful replies. Forewarned, as they say.

I can only help so far, greeninit. I have not (yet) had to change the pump but have had to change the anti siphon valve. Once the toilet is away from the wall, disconnect the power supply at the plug connector and pull the narrow plastic drain tube up through the floor. On the back of the control panel but under the main housing of the toilet there is a plastic tab which is part of the control panel. Push this in and the control panel will lift slightly. On the opposite side to the tab is a spring holding the panel in place. This will move as the panel is gently removed but it will only move so far because of the wiring. There are two thin white wires which go from the tank to the control panel. These should be removed from the panel. There is no positive or negative for these so it doesn't matter which way around they are when they are replaced. There are a pair of wires that go to the pump passing through the top of the anti-siphon valve to the control panel. Disconnect these (it leaves short tails on the panel). There are four screws that hold the header tank in place. Remove these, supporting the tank. There is also the water pipe connected to the top of the anti siphon valve. It may be better to not disconnect this as getting it back on can be a bit awkward especially if the pipe is old and getting less flexible. From memory I believe the anti-siphon valve just turns to release it.

This is where my knowledge ends I'm afraid. I'm not sure how the pump is held in place, I think it just hangs in the tank on a short piece of pipe but I'm sure it will be quite obvious.

Hope this helps.  

Thank's to JohnM20. 

That is good advice, of prewarned knowledge.

 I will tackle the job soon and let you all know of the out come.

just replaced the flush pump without taking out the toilet, remove the control panel with a couple of thin bladed screwdrivers, the springs are at 12 and 6 o clock, then the pipe to the toilet bowl, tricky but can be done, then twist the pump housing anti clockwise and manoeuvre out the housing and the pump,, the genuine Dometic pump was £55 bit I got a generic one off ebay for £9, fitted straight in, just had to put a couple of spade connectors on the wires and cut off the earth one, when refitting I replaced the fiddly spring clip on the pipe to the bowl with a jubilee clip. 

Just back from two weeks away and, yes, you've guessed it, more trouble with the Dometic toilet. This time it is the sealing ring between cassette and bowl that has started to leak. Not a difficult job to replace, just a costly one. For the seal it is over £35 for a rubber ring. Whilst searching for it online, I saw the Thetford seal that does the same job on Thetford toilets, it is only £13 !! Also during the search I found the Dometic elbow that is in the flush water pipe system. For this part Dometic want £18 !!!! I had already bought a pack of three completely adequate elbows for £4.29 from a PVC tube supplier. There is no physical stress nor is there any internal pressure on the elbow so why the original should suddenly fail is beyond me. I think we are being taken for mugs by Dometic. If I get any further problems with the toilet it is being ripped out and a Thetford installed. An expensive change, yes, but it's not always about the money especially when leaks are involved, and not just clean flush water

Interestingly it appears that Lunar, before they went bust, might have reverted to Thetford toilets. It wouldn't surprise me especially if they had received numerous complaints about Dometic equipment.