Having fitted a new bath with a pop up waste, I have found a major snag!. Although the pop up works perfectly when empty, or even with 3-4 inches of water, it is simply impossible to get it to lift with 6 inches of water in the bath! The system isn't man enought to lift against the head pressure, but there is no adjustment available on the cable to take out slack. I cant raise the plug bit any more, or it will leak Any ideas?