| Gallionella Ferruginea | A genus of stalked, ribbon-like bacteria which utilize iron in their metabolism, and cause staining, plugging and odor problems in water systems. (See iron bacteria.) | |
| Gallon | A unit of liquid volume; the U.S. gallon has a volume of 231 cubic inches or 3.78533 liters; the British (Imperial) gallon has a volume of 277.418 cubic inches or 4.54596 liters. | |
| Galvanic Cell | A cell which generates an electrical current, consisting of dissimilar metals in contact with each other and with an electrolyte. | |
| Galvanic Corrosion | The form of corrosion which occurs in a galvanic cell, in which one of the metals goes into solution; accelerated by high concentrations of dissolved minerals in water, which increases the electrical conductance; and elevated temperatures. (See corrosion, electrolyte.) | |
| Gate Valve | A valve with the closing element that is a disc which is moved across the stream, often in a groove or slot, for support against pressure. | |
| Gel Zeolite | A synthetic sodium aluminoscilicate ion exchanger. | |
| Giardia Lamblia | An intestinal parasite commonly found in water supplies originating in mountainous or wooded watersheds. It exists as a free-swimming protozoan-like organism in warm-blooded animals' intestines, causing chronic diarrhea, cramps, bloating and weight loss. Outside of the intestines, it forms a tough cyst that protects it until it finds a new host. Resistant to chlorine and most oxidizing agents, Giardia can be removed effectively through filtration below 1 micrometer. | |
| Giardia Lamblia | A protozoan frequently found in rivers and lakes, which can survive in water for 1 to 3 months, associated with the disease giardiasis. Ingestion of this protozoan in contaminated drinking water, exposure from person-to-person contact, and other exposure routes may cause giardiasis. The symptoms of this gastrointestinal disease may persist for weeks or months and include diarrhea, fatigue, and cramps. | |
| Globe Valve | A valve in which the closing element is a sphere, or a flat or rounded gasket, which is moved into or onto a round port. | |
| Gpg | Abbreviation for "grain(s) per gallon". | |
| Grab Sample | A single sample of material collected at one place and one time. | |
| Grain (Gr.) | A unit of eight equal to 1/7000th of a pound, or 0.0648 gram. | |
| Grain(S) Per Gallon (Gpg) | A common basis for reporting water analyses in the United States and Canada; one grain per U.S. gallon equals 17.12 milligrams per liter (mg/l) or parts per million (ppm). One grain per British (Imperial) gallon equals 14.3 milligrams per liter or parts per million. | |
| Gram (G) | The basic unit of weight (mass) of the metric system, originally intended to be the weight of 1 cubic centimeter of water at 4oC. (One pound is 454 grams.) | |
| Gram-Milliequivalent | The equivalent weight of a substance in grams, divided by one thousand. | |
| Gravimetric | Measurement of matter on the basis of weight. | |
| Greensand | A natural mineral, primarily composed of complex silicates, which possess ion exchange properties. (See manganese greensand, zeolite.) | |
| Ground Water | The water that systems pump and treat from aquifers (natural reservoirs below the earth's surface). |