Backflow – The backing up of water through a pipe in the direction opposite to normal flow.
Backwash – The process of thoroughly cleaning the filter by reversing the flow of water through it with the dirt and rinse water going to waste.
Bacteria – Single-celled microorganisms of various forms, some of which are undesirable or potentially disease-causing. Bacteria are controlled by chlorine, bromine or other sanitizing and disinfecting agents.
Bactericide – A chemical or element that kills, destroys, or controls bacteria.
Baking Soda – Chemically called sodium bicarbonate. It is white powder used to raise the total alkalinity of pool or spa water without having much effect on pH.
Balanced Water – The correct ratio of mineral content and pH level that prevents the water from being corrosive or scale forming.
Ball Valve – A simple non-return valve consisting of a ball resting on a cylindrical seat within a liquid passageway.
Base – Also called basic – A class of compounds which will react with an acid to give a salt. Base is the opposite of an acid. See alkali.
Bleach – This term usually refers to liquid chlorine (sodium hypochlorite 12% available chlorine). It is the same chemical used in laundry bleach but pool chlorine is 12% available chlorine while laundry bleach is about 5 to 6%% available chlorine.