(S (S (BASENP (PRP It)) (VP (VP (VBZ is) (RB not)) (VP (VBN known) (SBAR (WHADVP (WRB when)) (S (BASENP (NN water)) (VP (MD will) (VP (VB be) (VP (VBN turned) (ADVP (RB back) (PRT (RP on))))))))))) (PERIOD .))