Don't drown the miller when you make the tea.
drown the miller
idiomTo put too much water in something; overdilute.
Origin
disputed originOriginally drown the miller's thumb, meaning to go over the specified mark.
The recipe calls for a thick sauce, so be careful not to drown the miller.
By adding excessive water to the mixture, the novice cook managed to drown the miller and ruined the consistency of the soup.