Hey Jo, how ya doin? I just bought that same brand used and it had what seemed to be that same problem. I worked on it forever taking it apart and found out that when the shampoo holder is empty the unit will not supply the water nor suck it up so I would look into that. If it is not the tub itself you should trace out the water tubes and anything related to it to see if you have a clog somewhere. Hope that fixes it for you. :)
Musky
May 2010
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix vacuum cleaners.