GATE VALVE: The type that spins "lefty-loosey; righty-tighty."

GAS VALVE: An electronic valve in the pool heater that directs gas flow from the meter to the pilot and the burner tray.

GASKET: A gasket is a mechanical seal that fills the space between two objects, generally to prevent leakage between the two objects while under compression. Gaskets are commonly produced by cutting from sheet materials, such as gasket paper, rubber, silicone, metal, or a plastic polymer.

GROUND-FAULT CIRCUIT-INTERRUPTER: A GFCI device protects a circuit from branching off by de-energizing the path of electricity very quickly when it senses current loss. An important safety device around water (the pool?).

GROUT: a construction material used to embed rebars in masonry walls, connect sections of pre-cast concrete, fill voids, and seal joints (like those between tiles). Grout is generally composed of a mixture of water, cement, sand and sometimes color tint which is applied as a thick liquid and hardens over time, much like mortar.

GUNITE: A dry mixture of cement and sand mixed with water at the "gun"; hence the name. A gunite operator "shoots" the pool's rough shape, while finishers trowel after.