Rate at which plasma is cleared of solute free water is known as:
Free Water Clearance: 

Is regulated by ADH. 
It is the rate at which plasma is cleared of solute free water.

​Free-water clearance (CH20) is calculated as the difference between water excretion (urine flow rate) and osmolar clearance:
Free water clearance
Bound water clearance
Water clearance rate
Solute level clearance