Had exactly the same problem, where the stack fits into the waste tank the fitting is garbage. The lid of the machine pushes down on the stack and eventually causes a leak.
You should be able to re seal it with a good waterproof sealant that dries hard and still remains flexible (do this from the inside of the waste tank and underneath the waste tank where the motors are) then secondly unscrew the tube in the tank, take of the float valve and cut half an inch of the tube then re assemble everything . Once sealant has hardened fill the tank and check for leaks.
It’s a crap design from Prochem every time you put the wand on the carpet the lid flexes and pushes down on the stack putting pressure on the fixing, over time it will leak.
Hope this helps
John
