Gizzmo®
A hollow, collapsible plastic fitting used to plug the skimmer. If ice forms in the skimmer, the Gizzmo® will absorb the pressure from the expanding ice. It looks like a thermos bottle.

Gunite
A mixture of cement and sand which is sprayed onto the iron reinforced walls and floor of a hole to build a pool. The gunite surfaces are generally plastered.

Halogen
Any of a series of nonmetal elements of the periodic table, comprising fluorine, chlorine, bromine, iodine, and astatine.

Hand Skimmer
A net attached to a frame which is then attached to a pole and is used to remove large floating pollutants such as leaves and insects from the water's surface.

Hard Water
Water that is high in calcium, magnesium or other salts, which makes it difficult for soap to lather. Hard water also has a tendency to form scale.

Iron
Iron is a natural element that can cause the water to become clear brown or green in color. It can also result in staining of the pool surfaces. Iron can be controlled by the addition of a suitable sequestering or chelating agent.