Dometic Toilet Problem
My 2015 Lunar 524 has a Dometic toilet, CTW 4050 which has developed a problem. After I have filled the flush water tank to maximum and then flushed the toilet for the first time, even though the pump has stopped running water continues to constantly run into the bowl, probably due to siphonic action. This continues until the flush water tank is an estimated half full but by this time the bowl is almost full. Has anyone else had this problem or can offer any meaningful advice as to cause and rectification?
My additional concerns are that the bowl could overflow if we were not aware of it filling up and also that, if the waste cassette is getting ready for emptying there is nowhere for this excess water to be drained to. I have noticed black 'bits' in the flush water (although this is nothing new) and wondered if a 'bit' has stopped a valve from closing properly (I don't know if there is such a valve).
I must add that as a toilet I much prefer the Thetford made models that I have had in previous caravans. The blade operation on my Dometic is nowhere near as good as Thetford and although very regularly treated with silicone spray / grease it very quickly becomes difficult to operate the blade slide. The slide is thoroughly cleaned every two or three cassette emptyings. The handbook recommends this treatment once or twice a year if the toilet is used frequently.
I hope someone can come up with a solution as we will be going away again soon.
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No direct help but found this, perhaps you could figure it out from the diagram.
https://www.leisurespares.co.uk/brands/dometic/toilets-dometic/ctw4050/ctw4050-main
Worst case scenario, dont use the flush, keep the dilute pink in a pop bottle next to the toilet.
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John - you have my sympathy. We have a new Knaus Starclass 695 which had that toilet fitted. It was useless! Like you, I found the blade difficult to operate - despite there being plenty of silicone grease on it and my continual spraying with silicone. It leaked from the blade every time it was tipped up for emptying. The stupid, over-complicated telescopic handle jammed in the open position and then, finally, the flush mechanism packed up altogether. Added to which the wheels are so small on the cassette that they were useless on anything but smooth tarmac. All that in 5 months.
The dealer was unable to do anything under warranty other than to swap it for an identical model and based on their experience of continual problems with Dometic toilets, I paid them to have it changed to a tried and trusty Thetford. It went in perfectly other than the fact that the flush is now taken from the internal water tank, rendering the outside filler cap superfluous.
You may laugh - but on our recent three week holiday in Cornwall, it was a joy to use and empty as compared with all the hassle I had with that useless Dometic
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R&R, I'm sorry to hear that you have had similar problems to me re the blade mechanism but also pleased, in a way, that I'm not the only one to experience it. I wonder how many other CT members with the Dometic toilet have also had problems?
It has crossed my mind more than once about fitting a Thetford as a replacement but I guess it isn't a cheap option.
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John - if you do a search of other forums - as I did when I realised that Dometic toilets weren't as good as they made out - you will find loads of complaints similar to those I've highlighted. That was what swayed me in the end, to fix the problem once and for all.
I believe the dealer more or less did it at near cost price (so they said!) but it was still £600. However, when balanced against what we had paid for the van and the fact that we are unlikely to be buying another, it seemed justifiable to me. I just wanted something I could rely on.
The only problem you might have is whether or not you have an inboard water tank. Although the toilet has gone into the van with no signs that it has been changed, if it had had a header tank, the filler holes don't line up on the outside of the van - so they fitted the model without the header tank (although it looks as if it has one, if you understand). Your van might be different, but I doubt it.
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'I believe the dealer more or less did it at near cost price (so they said!) but it was still £600. However, when balanced against what we had paid for the van and the fact that we are unlikely to be buying another, it seemed justifiable to me. I just wanted something I could rely on.'
Or something reliable to go on?
Sorry, I'll get my coat.....
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I've been in touch with Dometic UK several times in the last few days. Their customer service department has told me that the cause is the anti-siphon valve which has probably got some muck in it. This can be caused by using too much rinse aid, ( something that I don't often use). A possible solution is to flush through several header tanks of warm water to try to dislodge the bits. Although some black bits did come through it didn't cure the problem.
Failing this as a cure, I was told at it would need the valve removing from inside the toilet housing, a job for a service engineer. In view of this I have now asked twice for the name / location of a service engineer in our general area. So far I've had no response from Dometic about this. Pretty poor service.
Although we have very few caravan workshops around us we do have quite a lot of boat yards including boat builders. They must put toilets into new boats but do they fit Dometics, that is the question.
When I first emailed Dometic I had a reply within hours but by strange that they can't email with the name of a service agent. Very frustrating.
Any new caravan purchase in the future will NOT have Dometic equipment fitted having experienced problems with the Dometic fridge and now the toilet in the current caravan.
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My overall impression of the Dometic toilet is that the design is over-complicated and the materials flimsy and just not up to the job. You did well for yours to last 4 years - we had all our problems within the first five months of ownership of the van and every time we used it, something else failed or didn't work properly. The flush mechanism failing was the final straw.
With regard to boats - they are a different beast altogether and I think you will find that Jabsco toilets are the preferred choice - another tried and tested brand that's been around for years in the marine world.
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I’ve just had to replace the sealing o ring under the blade of our Dometic toilet and was in disbelief at the cost of a rubber o ring £80 I think were all being taken for ride by these manufacturers. It’s cheap unreliable equipment at an eye watering price.
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You do not need to have an on board water tank to use a toilet without a flush tank, the water can be drawn from the Aquaroll.
Our previous van, a Sterling Eccles Emerald, had this arrangement, and it took us ages to remember that we had to keep the separate flush tank on our present van topped up!
The only slight drawback would be if you wanted to use and flush when stopped for, say, lunch, we got round this by having a small 10 litre water carrier that we dropped the external pump or water uptake into. This travelled in the back of the car.
The water was of course also handy for hand washing and kettle filling.
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I too have a Dometic in my Clubman SB and I hate it with a vengance - if I try to use the flush it ends up leaking onto the blade and then the floor, I have resorted to the pop bottle next to the loo! I've had it looked at but short of taking the unit out the problem couldn't be found.
I have been considering replacing it with a Thetford, so can I ask please what model Dometic did you have removed and what Thetford did you replace it with?
Thanks
Carole
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I will check these details later but I think the Dometic toilet was the CTW 4050 and the Thetford, the C263 - CSL. I know the Dometic had the ceramic bowl - and that it used to stain far more quickly than a plastic one!
We also had the identical problem that you describe in that flush water leaked across the top of the blade and into the caravan - despite there being loads of silicone grease on it and me spraying it every two or three days.
The Thetford replacement looks as if it has a flush tank but in actual fact it's a dummy - but that's why it goes in without any signs of replacement.
The reason the dealer went for this model is that the filler cap / hole in the side of the van doesn't line up, so it's not possible to have a Thetford with the integral flush tank and, instead, the flush water is drawn from the inboard tank (as all our water is). Although I was a bit dubious about this, it's turned out to be a bonus and I prefer it. It just means you have a redundant filler cap on the side of the van but no one but you knows this!
Although it was an expensive fix and I wasn't best pleased having spent a shed load of money on a new 'flagship' German van, the problem is now sorted, once and for all. Why, given the high quality of everything else in the van, Knaus fit this (expensive) rubbish toilet, is beyond me (and the dealer agreed!).
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Thanks for that. I don't have an on board tank but in my last caravan, that had a Thetford toilet, I was able to access the flush tank from inside so that maybe a possibility. You have certainly given me hope that there may be a real alternative to the Dometic, and a good pointer for further research
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As KjellNN has pointed out, it is apparently possible to fill the flush tank from the Aquaroll. Failing that, a retro fit of an inboard tank is quite easy - ours was put in prior to purchase by the dealer since the Starclass 695, for some strange reason. is the only TA in the range without one.
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I've just re read that post from KjellNN and can see that would work. I'm a bit tight on payload so that would probably be my best option, I may even save some weight by replacing the ceramic with plastic. The only issue I could have is the Thetford seems to come out further from the wall than my existing Dometic and it's cosy enough in the washroom as it is - a good excuse to visit a showroom or two and take some measurements - every cloud as they say
Thank you very much for your help.
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I have exactly the same problem with the blade on my Dometic loo (2018). It works ok for a while after liberally spraying silicone over the slide rods and applying silicone grease to the seal, but it’s only a question of time before it becomes stiff again. The Thetford toilet in my previous MH had no such problems in 6 years of use and seemed a more robust construction.
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Whitedragon - rest assured, it isn't deeper - and the reason I can be certain is that the carpet in ours fitted snugly around the base of the original Dometic and now there is a gap - at the front - of about an inch or so. Unless I pointed it out to you, you wouldn't notice - but it definitely isn't bigger.
The model number of the new Thetford is C263-CS
Hope this helps
Richard
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Just read the problems with domestic toilets and would like to add our experience.We bought a new coachman VIP in February,not realising the troubles with these toilets.Our van is now parked up waiting for its 3rd visit to the dealers for toilet repairs.First time was to cure the toilet flushing on its own.Luckily we heard the pump running when we stopped.Went into the van to find bowl full and pump still running.Dealer fitted a new circuit board after having the van for 2 days.We also discovered that the cassette was leaking!
Next time we had been on site for a day when the pump started up on its own again.Not so lucky this time,the water overflowed on to the floor.Back to the dealer for 2 weeks this time.We were then told problem was with pink fluid blocking a breather pipe and we shouldn't use it.
3rd problem was when travelling back from a week away discovered the control panel on the top was falling into the housing of the toilet.
We cannot understand why coachman fitted these without testing them,have now been told they have gone back to Thetford for 2020.
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Erny - sorry to hear this and, like me, you will be frustrated and angry that having shelled out a load of money, you are having these problems. One way or another, I would advise swapping it and if you can persuade the dealer to do it under warranty bearing in mind the Thetford is now fitted to 2020 models, so much the better. Virtually everything that could fail on ours - did - and I would never touch Dometic toilets with a barge pole ( or anything else for that matter!)
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I’ve toyed with the idea of replacing our Dometic toilet with a Thetford one for some time now. Ours is fitted to a Burstner Ixeo motorhome and its the one item that spoils an otherwise perfect vehicle. I have to spray the slide with silicone after every empty and the flush mechanism’s performance has always been less than adequate. The design of the Dometic unit is abysmal. How it ever progressed passed the development stage has always been a mystery and an annoyance to me. Sounds like the Thetford loo is a viable alternative.
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I would do it. It's now five months since the toilet was changed and its had 60 days use since then without a single problem, whereas with the Dometic, something went wrong every time we were away. As I said earlier, the Dometic design is over-complicated and the materials used are flimsy. I could have gone down the 'not fit for purpose' route but I suspect that wouldn't have got me anywhere other than putting my blood pressure up. At least it's sorted now.
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Thetford are not without problems, including the one where it starts flushing spontaneously! Much debated over the years on SwiftTalk.
In the case of the Thetford it seems to be a problem with the control board getting damp. We have suffered from it and in the end I resorted to fitting an additional button on the top of the tank, which interrupts the power, so now both it and the flush button have to be pressed simultaneously.
100% successful.
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Well, hopefully, with our new one not having an internal flush tank, that shouldn't be a problem!
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Hi Richard,
We are about to buy a van with a Dometic toilet and was interested to see you have actually swapped over to a Thetford, which is what I’d like to do but wasn’t sure if it was possible, may I ask who swapped yours over please?
Regards
AlannBailey
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Having read the issues on the German made Dometic cassette, it would seem that my problem is nothing to moan about. "Ive mislaid the dump cap on my cassette, probably fallen down the hole. To get a replacement it will cost me £37.10. which would have made "Dick Turpin" blush.
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Another vote for Thetford. My Dometic toilet is flimsy and hard to operate requiring regular silicone grease/spray to keep it useable. My old van with a Thetford had no such issues and was much more robust - no pretty colours tho’
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Hi Alann
Sorry - only just seen this after the thread was resurrected. The work was done by ALV at Tebay - the dealer from which we bought the Knaus. It turned out to be quite an easy job - it looks fine and, touch wood, we haven't had any problems since it was installed. As someone said earlier, it was the one thing that was spoiling an otherwise perfect van and I'm pleased I made the decision to shell out the extra cash and get it sorted once and for all.
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We have a Dometic toilet in Our 2018 Coachman 520 VIP. The toilet cassette cracked on the underside after about 3 uses and within one year of purchasing the caravan brand new in 2018. We informed the dealer who contacted Dometic who said that I had damaged the cassette as it had some scuffing on the underside of the cassette. To cut a long story short this has been ongoing for well over a year with the dealer saying that they had informed me that Dometic had refused to replace under warranty, I don’t recall receiving any such notification, and me contacting Dometic directly. They reaffirmed their decision that it was not covered under warranty as there was some scuffing on the underside of the cassette so it was damaged by me. This turned into rather an irate phone call and raised a couple of questions.notably I asked who is responsible for consequential damage and they informed me that it would be me as it is now a known problem so I should replace the cassette but Dometic also made me feel as though mine was the only cassette that had failed in this way. On mentioning this on a Coachman forum I found that numerous others had had similar problems. Since I now cannot use the toilet unless I replace the cassette does this make the whole caravan not fit for purpose? Given that Coachman have gone back to using Thetford toilets I’m surprised that Coachman haven't done a recall and replaced this pile of junk that they insisted on using in their flagship van. Another problem that has developed is that the plastic film cover to the flush button has also holed. I am now waiting again to see what the dealer comes back with but am not holding my breath and considering going to trading standards as the cassette is not fit for purpose making the whole caravan not fit for purpose. I would advise anyone thinking of buying a caravan to avoid any with Dometic products fitted
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Unlike the Thetford, the Dometic cassette is actually made of a much thinner, brittle plastic. I actually found a YouTube video of how to repair a crack in the Dometic cassette which made me think that it wasn’t an uncommon problem.
Another thing that sort of amused me - anyone found a way of emptying the cassette and holding the vent button down at the same time - without using three hands!😂
Given my previous comments, I can’t think of one single design feature of this toilet that is worth a recommendation.
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I agree wholeheartedly with the comments about the Dometic loo. After a frustrating couple of years I recently changed mine for a Thetford C220 series unit. The changeover was relatively easy although i did have a problem with height tolerances on the Thetford loo between the casssette and the fixed part of the unit. To their credit Thetford did get back to me with some advice but in the end I’ve had to pack the cassette bottom rail by 3.5mm. Its no big deal and it would be an exaggeration to say its a pleasure to use and to empty it but I’m sure you know what I mean.
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This is an old post, but for the sake of others, I would like to share my experience.
First of all, in the absence of a manual, I more or less dismantled the toilet (Dometic CTW4050). Probably a mistake.
The water filler for the flush must be removed from outside the van. It has a pipe with O-ring extending into the flush tank. You can then lift the unit off the internal wall plate (hook) that retains it.
Find the 6 long screws securing it to the floor of the van, and remove them, not the 6 screws that hold the damn thing together. You should be able then to lift it off, unplugging the supply first, and extracting the breather hose that presumably goes through the floor.
The flush water pipe is relatively heavy and ours has become stiff. Where it entered the outer bowl, there is a 90 degree elbow made of flimsy plastic that had deteriorated and literally crumbled. This is what was leaking. You need to remove the seat (lever up with thin blade at each of the triangular marks on the seat) to reveal the screws holding the 'flush ring'. You should then be able to remove the bowl (sealed in to the base), and gain access to this fitting. Nasty spring steel clips are used to retain the hose, awkward to release by easing the spring with pliers. They also rust. There is no support for the hose or wiring - suggest self adhesive anchors and cable ties.
The other end of the flush pipe on the tank goes into another naff fitting, which again broke. This also includes the anti syphon valve. Our tank was heavily polluted with black residue presumably from leaving pink fluid in the tank for too long. Some people say don't use it. The valve was presumably not working due to residue. Incidentally, the pump motor wires pass through a hole in this fitting, so that if the tank is overfilled it will spurt out of this, possibly over the electronic control unit?
I attach a photo showing the remains of the elbow, and the tank cap with syphon..
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