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Waste water leak.


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My Hymer MLT is fitted with a motorised waste water dump valve, switched on/off inside the garage. When closed, I have no water leaks anywhere.


However, when the dump valve is operated, water flows from the outlet nozzle but also leaks copiously from around the bottom of the insulated cover..


The main waste pipe enters the insulated cover thro a plate screwed on to the insulated cover with 4 screws. The pipe is sealed with mastic where it enters the plate. Has anybody been behind this plate to inspect/replace the dump valve.?


I suspect the valve is functioning OK but the pipe on its outflow has detacted itself somehow from the valve. I am currently away with the van for 5 weeks and am somewhat reluctant to get in there, in case I make the situation worse and/or find a part I cannot replace. I would welcome any thoughts on this problem. At home I would be taking it apart to investigate but would welcome any insight available just in case I make it worse.

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  • 1 month later...

Following my post on 8th July, (nobody seemed to have had this problem), I dived in to see what was wrong. I found that the outlet pipe (40mm OD) from the motorised ball valve had come completely out of the output socket ( 41mm ID) and was just resting on the output face. An O ring had been fitted in a groove (37mm OD) in the output pipe but was badly perished and simply pulled apart when handled. it was also evident that that pipe had never been fully inserted into the valve because the brackets holding the pipe to the van floor and the surrounding pipe were covered in black overspray and had never been moved. In their positions, the end of the pipe carrying the O ring, simply could not have been inserted by more that 5-6mm and the O ring had never engaged the ball valve socket, which was 40mm deep.


That was the problem I found but the solution proved much harder and is the reason why I now take the trouble to update this thread. Nobody seemed able to supply a new pipe fitted with the appropriate O ring, so I had to set about finding the correct size O ring so I could reuse the pipe. To cut a very long story short (specifying the correct O ring dimensions and stretch is a whole new ball game and I got it wrong 3 times), I identified the German manufacturer of the outlet pipe, who was able to confirm the required detail for the O ring, even though they could not supply. The dimensions required were ID 35 mm, Cross-section 2mm. A company called Simply Bearings were able to supply and once fitted with a little silicon grease, has finally fixed the leak. So if anyone else has this problem, this is the definitive answer... assuming you have the same pipe fittings....??

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