a pair of liquid containers at {TAIL ~ substantially the same level} including {HEAD ~ a water container} and a detergent container 
a pair of liquid containers at { TAIL ~ substantially the same level } including { HEAD ~ a water container } and a detergent container
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH