Durham succumbed by one wicket in their penultimate match in the ECB Women’s County Championship Second Division match.
Durham were all out for 117 against Wales, with Laura Hockaday (32), Elysa Hubbard (23), Laura Ellison (12) and Hayley Falla (11) the only batters to reach double figures.
Wales were reduced to 78-8 in their reply, but their tail saw them home, despite four wickets from Rachael Petherick and three from Hubbard.
The final game is against Essex in a potential relegation decider at Durham City on September 13.
Second-bottom Essex trail third-bottom Durham by 14 points but have a game in hand.