The average swimmer in the pool of the Indoor Athletic Building assumes that the water in the pool is changed once or twice a day, as is the case in most pools. As a matter of fact it is renewed but twice during the entire year, although it is constantly running in and out of the pool. This is made possible by a complicated system of baths through which the water passes. The pool is 75 feet by 40 feet with depths of 7 1-2 and 11 1-2 feet at the ends. Its capacity is 225,000 gallons, and it takes ten hours for the centrifugal pumps, which are in action while the pool is being used, to circulate this quantity through the cleansing apparatus.

On leaving the pool, the water goes through a "haircatcher" which removes any lint from bathing suits or any similar material which has remained in the water. After this, it is heated to between 72 and 75 degrees. It then runs through two coagulant pots, one of soda ash and the other of alum, which prevent undue acidity. The main work of filtration is done by 27 tons of special graded Cape May, New Jersey, fine sand, through which the water seeps. Before entering the pool again, the water is impregnated with chlorine gas, which lends a greenish color and which disinfects the water while it is in the pool. The results of this addition can be tested by comparing a test tube full of water with a graded color chart. In addition, the floor of the tank is periodically cleaned by being subjected to the suction of a large curry comb, connected by a hose to the vacuum end of the pumps.

On Saturday evenings or on Sundays the filters themselves can be cleaned by forcing the water back through them. Some waste escapes through the over flow gutters, which are closed, however, during meets to assure a quiet surface.