Definition
Synonym of down the toilet: wasted; irretrievable.
Also Said As
How People Actually Use It
Popular UK expression, especially 20 or thirty years ago = when your life or a situation is fast deteriorating or going rapidly downhill Tubes = probably has its origins in toilet tubes or pipes
"We were good at first but our relationship is going down the tubes Our season has gone totally down the tubes and looks like we'll be relegated"
Source: Urban Dictionary