Fluid reservoir

A fluid reservoir made of non-magnetic material comprising two chambers communicating with a common well, a single reservoir refill aperture located between the two chambers and above said well and communicating with said well, a float disposed in said well and bearing a permanent magnet and a switch outside said reservoir under the bottom of the well, said switch being actuated by the magnet when the float is at a predetermined level in the well, said well communicating with the two chambers through vertical narrow slots, the location of the lower ends of said slots being such that a predetermined quantity of fluid is retained in one chamber in case of fluid depletion of the other chamber, the upper ends of said slots being above the maximum fluid level admissible in the reservoir to permit fluid refilling of the chambers from said well via the single reservoir refill aperture up to said maximum fluid level.