The system disclosed is for controlling the iodine level in a water supply in a spacecraft. The system iodinates drinking water as necessary. It includes an iodine accumulator which stores crystalline iodine, an electro-chemical valve to control the input of iodine to the drinking water and an iodine dispenser. A pump dispenses fluid through the iodine dispenser and an iodine sensor to a potable water tank storage. The iodine sensor electronically detects the iodine level in the water, and through electronic means, produces a correction current control. The correction current control operates the electro-chemical iodine valve to release iodine from the iodine accumulator into the iodine dispenser.