But {TAIL ~ water} may pool at {HEAD ~ the top end} of the array, and on structures such as rooftops, the pooling may have undesirable consequences 
But { TAIL ~ water } may pool at { HEAD ~ the top end } of the array , and on structures such as rooftops , the pooling may have undesirable consequences
OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH