one of mine did the same thing up until and hour ago, then I threw it in the bin 
I have a theory though, the plastic is very bendable, and the mouth piece is a hard rubber, maybe its warping the plastic, allowing air in, loosing the vacuum, causing it to flow like a river.
I started a new one, and it's fine. For now anyway. But I suspect that it will leak in a fill or two.
	
		
			
		
		
	
			
			I have a theory though, the plastic is very bendable, and the mouth piece is a hard rubber, maybe its warping the plastic, allowing air in, loosing the vacuum, causing it to flow like a river.
I started a new one, and it's fine. For now anyway. But I suspect that it will leak in a fill or two.
 
				
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		