I am an English speaker. This lavoir is down a small road off the roundabout on the D668 at the entrance to Monségur. The road looks like a private road but it is not.
[I have a small collection of Lavoir pictures on my web site here:https://www.flickr.com/photos/79565611@N08/sets/72157647790678663/
This lavoir is not easy to find. In Riocaud on the North side of the church, take a sloping farm track going West down through the field, then bear right for 50 meters, and it is on the left at the field edge. It is not close to the large neglected pond.