This document  is  an American Water Works Association (AWWA)  standard.  It  is  not a  specification. AWWA  standards  describe minimum  requirements  and  do not  contain  all of  the  engineering  and administrative  information  normally  contained  in  specifications.  The  AWWA  standards usually contain  options that  must be evaluated  by the  user  of the  standard.  Until  each optional feature  is specified  by  the  user, the product or service  is not  fully defined.  AWA publication of  a  standard does not  constitute endorsement of  any product  or product  type,  nor  does  AWWA  test,  certify,  or approve any  product.  The use  of AWWA tandards is  enti.rely voluntary. AWWA  standards are intended  to  represent  a  consensus of  the  water  supply industry  that  the  product  described will provide satisfactory  service.  When AWWA  revises  or withdraws this  standard,  an official  notice  of action  will  be placed  on the  first  page  of  the  classified  advertising  section  of  Journal AWWA.  The action  becomes  effective  on the  first  day  of the  month  following  the  month'  of  Journal  AWWA publication of  the  official  notice.