These days, we associate footwashing with Maundy Thursday or Holy Thursday services. It turns out to be a fairly new practice, at least at the parish level.
In 2010 I graduated from the Graduate Theological Union in Berkeley, CA, with a MA in Liturgical Studies. My thesis was entitled “Footwashing in the Western Christian Liturgy : The History of a Ritual Element”. It traced the course of footwashing as a feature in Christian liturgy through the centuries.
I’ve provided the whole thing for you to download, if you like.