The Watermaster® Single Point Battery Watering Vent Cap is the heart of the Watering System. The Cap consists of a small bowl above the cell and a Level Sensing Tube (LST) which protrudes beneath the bowl into the battery cell. It has absolutely no moving parts shutting off the replenishment water flow into the cell.

The Cap requires low pressure (1,5m) such as the natural reliable force of gravity to direct water into the cell, the universal tendency of liquids to seek one level, to compress air in the LST and the surface tension of water to cause shut off. The electrolyte level is determined by the length of the LST. At the bottom of the bowl is a small hole (orifice) allowing water to flow into the cell and a plate immediately above the hole which maintains an air-tight water seal, preventing the air in the LST from escaping upwards. As soon as the rising electrolyte reaches the bottom of the tube, the air pressure within it increases, preventing further flow of water through the hole.

Certainly the Watermaster Cap does have a float-activated valve, but this only prevents water from overflowing from the bowl when the flow into the cell has been previously stopped by the rising electrolyte and surface tension seal. The float-activated valve does not play any significant part in determining the flow of water to the cell. The float and valve only have contact with the incoming water and are never exposed to the sticky sludge in the electrolyte. It provides a unique filling safeguard against inadvertent over topping of the battery cells.

The length of the LST complies with the electrolyte levels of virtually all cells in use, however, different levels can easily be accommodated by simply extending or shortening the tube. Extension tubes are available if necessary and are included in the price of the Cap.

The design is patented worldwide. The millions of caps in operation proves the product's reliability. Kits are available for all size batteries from small golf-cart size through to large mining and traction batteries.