spospe Posted September 18, 2021 Share Posted September 18, 2021 We have an Auto-Sleeper Warwick Duo fitted with a Thetford C400 toilet and overnight it emptied the flush tank into the waste tank, seemingly without running the flush pump. Has anyone experienced this before and any ideas on how to prevent it happening again? This is the first time in 20 years that this has happened to us and we have never heard of it happening to anyone else: Ideas (or solutions) please. Link to comment Share on other sites More sharing options...
Tracker Posted September 18, 2021 Share Posted September 18, 2021 Not sure, no expertise as it never happened to us but first guess suspects continuously running pump as the cause, dodgy switch comes to mind? Can I presume the pump was not running continuously as you would probably have heard it but as it is designed to run wet it may not have survived pumping air from a dry tank? Is the pump working OK now - and does the switch turn it on and off OK? Link to comment Share on other sites More sharing options...
spospe Posted September 18, 2021 Author Share Posted September 18, 2021 Rich Pump working OK at present and certainly was not heard running in the night. Pump runs when switch is pressed and stops when switch is released, sounds normal. I wonder if a syphon action was involved, but I have never heard of this happening before, hence this query. Link to comment Share on other sites More sharing options...
tonyishuk Posted September 18, 2021 Share Posted September 18, 2021 our toilet does not have a flush tank so I assume the flush tank is above the toilet seat where the flush discharges. If so my guess is that the fluid siphoned from the flush tank. I have no idea what is involved with the plumbing but would guess that a seal on the pump has gone where it would normally hold back the flush after pumping, or similarly some type of valve that only works when pressure from the pump. You maybe lucky, may be a one off incident where some muck held the seal open, and then blown through at the next flush. Rgds Link to comment Share on other sites More sharing options...
Keithl Posted September 18, 2021 Share Posted September 18, 2021 I thought the problem sounded familiar! Here you go, try this thread... https://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Thetford-toilet-problem/58291/ Keith. Link to comment Share on other sites More sharing options...
Tracker Posted September 18, 2021 Share Posted September 18, 2021 My memory is not what it was Michael but as I recall the loo in our Warwick Duo was a bench type with a built in water tank surrounding the bowl that was filled from the outside through a movable capped spout inside the waste tank access hatch? The flushing water when pumped came out of a spout close to the rim of the bowl, which is generally higher than the water level inside the tank itself and as such it is hard to imagine how water can get from this into the waste tank by syphoning when the bowl blade is closed - unless there is some pressure sensitive 'gubbins' (technical term) that allows water to pass directly from one tank to the other hidden under the bowl in the hatch? The flushing tank was only a few litres less than the holding tank as I recall so unless you had only just emptied it was there capacity for (from memory) around 15 litres of flush go into a 19 litre holding tank - if not where else might it have gone? I expect you know this already, but my understanding is that to syphon the outlet needs to be lower than the source water level and needs to be in a continuous tube fully filled with liquid and no air - and that does not seem to appy here - or does it? Perhaps your van being newer than ours has an 'improved' loo? Sorry, there probably is a simple answer, but it is beyond my simple experiences!! spospe - 2021-09-18 8:38 PM Rich Pump working OK at present and certainly was not heard running in the night. Pump runs when switch is pressed and stops when switch is released, sounds normal. I wonder if a syphon action was involved, but I have never heard of this happening before, hence this query. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted September 19, 2021 Share Posted September 19, 2021 Spospe’s toilet will be a Thetford C402 bench-style model and a diagram and spare-parts list can be downloaded from here https://www.thetford-europe.com/gb/products/toilets/cassette-toilets/c402-x-right Logically, if the water in the flush-tank were siphoning into the cassette, the water must have been passing through the inlet of the toilet’s submersible pump that would be near the bottom of the flush-tank and (presumably) below the water outlet in the toilet bowl. As Tracker has said, this makes siphoning doubtful. On the other hand, if siphoning does start, it won’t stop until the flush-tank is empty and, if the pump wasn’t operating, there’s no obvious alternative explanation. (If this happened when the flush-tank was full and the cassette’s blade-valve was closed, there would be a flood in the bathroom. Even worse, if the flush-tank and the cassette were both full and the blade-valve was not fully closed, the ‘flood’ would be very unpleasant.) Link to comment Share on other sites More sharing options...
paulmold Posted September 19, 2021 Share Posted September 19, 2021 I had it happen on a swivel bowl toilet. That was a faulty switch which continually ran emptying the tank. This can't be the switch because it operates normally so I've no idea. Link to comment Share on other sites More sharing options...
spospe Posted September 19, 2021 Author Share Posted September 19, 2021 I have no idea other than syphonic action. The flush tank was full and the waste tank was more or less empty, so there was space for all the flush water. The blade seal was not tightly closed, so the water could drain from the bowl into the waste tank. Potentially quite nasty and unpleasant, especially as it was so quiet and I only found it in the early hours. I'm not sure if our toilet has a 'vacuum' valve, but it does not draw water from the main vehicle water tank (it has its own tank). Thanks for all the suggestions / help, if I find out any more I will post it here. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted September 20, 2021 Share Posted September 20, 2021 Spospe The link I provided in my posting of 19 September 2021 9:05 AM above indicates that C402 toilets do NOT have a ‘vacuum breaker’, though C403 toilets (that have no integrated flush-water tank) evidently do have that part. This Thetford file covers repairs to C400 toilets https://www.thetfordservicenet.com/wp-content/uploads/C400-Repair-Instructions.pdf About a quarter of the way down is a section describing how to replace the water-pump of a C402C/X toilet and a ‘cut-away’ photo (attached below) shows the pump’s location in the front-left bottom corner of the toilet’s flush-water tank. There’s also a YouTube video covering pump replacement The parts-list drawing indicates that there’s nothing ‘clever’ about the connection between the pump and the water outlet nozzle under the rim of the toilet bowl: the pump connects directly to the nozzle via the plastic hose shown in the photo. Given where the pump is located and the simplicity of the pump-to-nozzle connection, I believe the ’siphoning’ hypothesis idea is a non-starter. Even if the flush-water tank were completely filled so that the level of the water in it were higher than the nozzle in the toilet bowl (I don’t know if that can actually happen) and water began to flow spontaneously through the pump to the nozzle, once the water level in the tank dropped below the nozzle’s position in the bowl, water would cease flowing. Basically, even if one were to allow the possibility of siphoning, a full water tank could not empty completely. If water could siphon into the toilet bowl when a C402 toilet’s flush-water tank is full, it would be a well-known phenomenon and, essentisally, the toilet would be unfit for purpose. But there are no online complaints of this happening. And if the siphoning idea has merit, it should happen every time you fill the flush-water tank - so you should be able to replicate the ‘emptying’ experimentally. Paulmold mentioned a faulty flush switch. The control-panel switch seems more likely to have been the culprit in your case even though everything is now back to normal and you say that you didn’t hear the pump running during the night when the flush-water tank emptied. You could replace the control-panel (about £50) as a precautionary measure, or just hope the problem won’t reoccur. Link to comment Share on other sites More sharing options...
Keithl Posted September 20, 2021 Share Posted September 20, 2021 Derek Uzzell - 2021-09-20 8:38 AM You could replace the control-panel (about £50) as a precautionary measure, or just hope the problem won’t reoccur. Or turn the electrics off at night. Keith. Link to comment Share on other sites More sharing options...
spospe Posted September 20, 2021 Author Share Posted September 20, 2021 I agree that a faulty switch would provide a simple answer and indeed this was our first thought, but and it is a big but, we did not hear the pump running at all. When the problem was first found (by myself at about 3 AM) the pump was not running at all and the flush tank was empty, the waste tank was full (light on) and the toilet bowl about half-full. Perhaps the best thing is to replace the switch as a precaution as turning the power off at night also turns the heater off and this is not something we wish to do. I will report any other findings. Link to comment Share on other sites More sharing options...
Tracker Posted September 21, 2021 Share Posted September 21, 2021 spospe - 2021-09-20 6:24 PM Perhaps the best thing is to replace the switch as a precaution as turning the power off at night also turns the heater off and this is not something we wish to do. I will report any other findings. You might be able to get at the wiring via the outside locker? If so an on/off switch operable from within the loo should not be too hard to fit - but it might need to be showerproof - unless you can fit it on the outer wall close to the door so it can be switched on on when needed! Link to comment Share on other sites More sharing options...
rajohno Posted September 21, 2021 Share Posted September 21, 2021 I would check all the pipework between the pump and flush for damage leaks and lose connections, it sounds to me, no matter if it seems impossible, the tank is self syphoning somehow. this could be due to pressure changes which can occur if the flush tank is warmer than than the ambient temp or being pressurised by aircon or domestic fans within the habitation, it dosn't take a lot of variation in temp or pressure to encourage the syphon action. Link to comment Share on other sites More sharing options...
spospe Posted September 23, 2021 Author Share Posted September 23, 2021 Thanks again for all the suggestions and here is an update on what I have found so far. I have pulled the switch unit out, which seems to be as per Derek's photo above and it is both dry and corrosion free. Nor is there any sign of any kind of damage, to either the push-button switch, connectors, or wiring. The pipework seems to be as per normal and the pump itself seems OK. I agree that there does not seem to be the possibility of syphonic action as the pipework as installed would not support it. I am left with a puzzle, the pump was not running when the problem was discovered, the flush tank was empty, the waste tank was full and the toilet bowl was half-full (of flush water). The black plastic blade was open just enough to allow the flush water past it and into the waste cassette (otherwise the shower tray would have been flooded). The pump switch is the obvious culprit, but no one else seems to have heard of the problem before. Surely this is not a 'one -off' unique happening? Link to comment Share on other sites More sharing options...
Brian Kirby Posted September 23, 2021 Share Posted September 23, 2021 But, with a full cassette, an empty flush tank, and standing water in the toilet bowl, any attempt to remove the cassette, (bearing in mind the blade valve is on the cassette, and if it is not fully closed it usually blocks removal of the cassette - for obvious reasons), would have released the water from the toilet bowl into the "bench" base that houses the cassette. And yet, you haven't mentioned the inevitably resulting flood. Was there one, or had the part closed blade valve actually prevented some of the water in the bowl from entering the cassette until, presumably on seeing the standing water in the toilet bowl, you fully opened the blade valve, only then discover that the cassette itself was full? It doesn't explain why water would continue to flow into the toilet bowl after the flush button was released, but it might explain why there was no flood when the cassette, as I assume you must have done, was removed. Have you tried contacting Thetford to see if they have any experience of similar problems? If the bench itself houses the flush water, placing most (if not all) of that water below the level of the flush nozzle on the toilet bowl rim, syphonage of water from tank into bowl via the nozzle seems for all intents and purposes, impossible. And yet, that seems to be what actually happened. The only other logical answer is that the pump had, for whatever reason, been running. As it had stopped before you discovered it, it seems it must have continued running after a previous use, the pump noise possibly having been masked by other noise from elsewhere. Clearly the pump itself works OK, so the most likely culprit seems to be the flush button sticking on when actuated, and then later releasing. Might high recent temperatures have caused the button to stick? Is there any lubricant on/in the switch mechanism that has gone sticky sufficient to prevent the actual switch contacts opening when the button is released? Link to comment Share on other sites More sharing options...
Keithl Posted September 23, 2021 Share Posted September 23, 2021 Brian Kirby - 2021-09-23 4:03 PM But, with a full cassette, an empty flush tank, and standing water in the toilet bowl, any attempt to remove the cassette... would have released the water from the toilet bowl into the "bench" base that houses the cassette. And yet, you haven't mentioned the inevitably resulting flood. The method of dealing with a full tank and a full bowl is to swivel the emptying spout outwards WITHOUT removing the cassette, and then carefully unscrewing the cap over a bucket or bowl. The contents will discharge until the level is below the blade valve which can then be closed and the cassette removed as normal. Keith. Link to comment Share on other sites More sharing options...
laimeduck Posted September 23, 2021 Share Posted September 23, 2021 Keithl - 2021-09-23 5:43 PM Brian Kirby - 2021-09-23 4:03 PM But, with a full cassette, an empty flush tank, and standing water in the toilet bowl, any attempt to remove the cassette... would have released the water from the toilet bowl into the "bench" base that houses the cassette. And yet, you haven't mentioned the inevitably resulting flood. The method of dealing with a full tank and a full bowl is to swivel the emptying spout outwards WITHOUT removing the cassette, and then carefully unscrewing the cap over a bucket or bowl. The contents will discharge until the level is below the blade valve which can then be closed and the cassette removed as normal. Keith. Ahhh .... reminds me of a "Blaster Bates" monologue.... "A shower of **** over Cheshire!" Link to comment Share on other sites More sharing options...
Brian Kirby Posted September 23, 2021 Share Posted September 23, 2021 Thanks for that Keith. I hadn't realised one could do that. Wouldn't want to try it on ours, as the spout is quite a way into the van, making placing almost anything large enough under it tricky to say the least. Hope to avoid that one! Worth knowing though, just in case!! :-D Link to comment Share on other sites More sharing options...
spospe Posted September 23, 2021 Author Share Posted September 23, 2021 Brian I drained the water in the bowl as per Keithl's mention above (swiveling the emptying spout of the waste tank), this worked very well at 3 AM in the dark! I have not spoken to Thetford, mainly as I cannot find a Customer Support phone number, only the telephone numbers of dealers. Just to reiterate again, the pump and its switch work fine, there is no sign of the switch (a kind of push button) sticking on, nor is there any sign of corrosion. The pump was not working on discovery, yet worked perfectly well when I tried it on discovery of the problem. Sleepwalking and unconscious toilet use? Link to comment Share on other sites More sharing options...
spospe Posted September 30, 2021 Author Share Posted September 30, 2021 Been away for four nights without any further problems: now stumped. To empty the flush tank takes a good long press of the pump button, not something you could do accidentally, syphoning seem impossible, a faulty switch does not seem at all likely (it has been examined and seems perfect). There has to be an answer, but what is it? If I find anything more it will be posted here. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted September 30, 2021 Share Posted September 30, 2021 spospe - 2021-09-30 3:11 PM ...There has to be an answer, but what is it? Sleepwalking perhaps... Link to comment Share on other sites More sharing options...
Geeco Posted October 2, 2021 Share Posted October 2, 2021 laimeduck - 2021-09-23 4:22 PM Ahhh .... reminds me of a "Blaster Bates" monologue.... "A shower of **** over Cheshire!" Jeremy an old friend from Bradford introduced me to Blaster Bates on 33rpm long play vinyl. Being a foreigner I had to play the recording three times to finally decifer what he was saying. Once understood he was very funny. The nearest we had here was "Gelignite "Jack Murray. During the first round Australia car rally way back when, he was reputed to have thrown the odd stick into the bush to possibly scare other drivers. But I digress. Cheers, Link to comment Share on other sites More sharing options...
laimeduck Posted October 2, 2021 Share Posted October 2, 2021 Geeco - 2021-10-02 6:43 AM laimeduck - 2021-09-23 4:22 PM Ahhh .... reminds me of a "Blaster Bates" monologue.... "A shower of **** over Cheshire!" Jeremy an old friend from Bradford introduced me to Blaster Bates on 33rpm long play vinyl. Being a foreigner I had to play the recording three times to finally decifer what he was saying. Once understood he was very funny. The nearest we had here was "Gelignite "Jack Murray. During the first round Australia car rally way back when, he was reputed to have thrown the odd stick into the bush to possibly scare other drivers. But I digress. Cheers, Gary Blaster Bates would have been able to empty a Thetford Cassette in seconds! A genuine and total character ...... and whats more most of the tales were true! (albeit a tad embelished!) Jeremy https://en.wikipedia.org/wiki/Blaster_Bates Link to comment Share on other sites More sharing options...
spospe Posted October 27, 2021 Author Share Posted October 27, 2021 Been away for two weeks without any problems. I have dismantled (as far as possible) the push-button flush switch and can find nothing wrong. I have tried to start a siphon going by overfilling the flush, but it just does not work. The only way for the toilet to act as it did, is by the pump running and for this to happen the push-button must be pushed. Baffled. Sleep-walking? Link to comment Share on other sites More sharing options...
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