In October 1819, Tench was reactivated as commandant in the Plymouth division at the age of 61. Although he and his wife had no children of their own, in 1821 they took responsibility for three nephews and a niece when the four children were orphaned. At the time, Watkin Tench was 63 and his wife was 56. Watkin Tench resided in Chapel Street, Penzance, in the house constructed by Richard Oxnam's grandfather. He lived there from 1818 until 1828.

In July 1827, Tench retired