Ferrofluid can be used effectively as a liquid seal for rotary shafts to seal off gasses. However, this technology tends to be less effective when sealing off a liquid. In such applications, one major problem is the degradation of the fluid when it comes into contact with the liquid. This paper presents details of a method for replacing the ferrofluid in the seal without pressure loss, in order to improve the lifetime of the seal. A test set-up has been designed to comply with all contemporary knowledge covering ferrofluid–water interface seals and to improve on it by adding a replenishment method. Using a finite element analysis model to predict the pressure capacity, the results show the measured capacity conforms to the model. In addition, the set-up has produced promising results on the stability of the seal, when water is used as a medium in the pressure chamber