Depends on the shape of the vessel.First, find the volume of the vessel, according to its dimensions and the formula for the volume of the shape of the vessel. Convert it into the units given by the rate at which the vessel is being filled.Eg. If your volume is in cm^3 and the rate of filling is in m^3, convert it appropriately.Then divide the volume of the vessel by the rate of filling. The answer will be your time, which will be in the units as described in your rate of filling.If the filling rate and volume are in cm^3 per minute, then your answer will be in minutes too.Hope this helps!