Mine is also doing the same thing. Doesn't help that the Vokera customer care line works in office hours only!
Advice from other people has been to pour hot water over your external pipe (the one that links to your waste pipe) and hold a hairdryer to the internal pipe (rubber pipe that leads to plastic white pipe) in case it has frozen and is blocked wiht ice.
Didn't work for us but it may work for you.
Leanne
December 2010
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