There is no Elizabeth Waters baptised at Uzmaston circa 1820.
There is no Thomas Lewis baptised at Mathry circa 1817.
I note a William Waters was of Boulston when he mrd Anne Jenkins at Uzmaston in 1819, Therefore I wonder if your William has a connection with William Waters of Bouston whose will was probated 1829. See ; http://cat.llgc.org.uk/cgi-bin/gw/chameleon?skin=profeb&...
Unfortunately your William is not mentioned as one of the 5 sons.