Example - for a 3-bedroom, 2,000-sq.ft. home, with an exhaust-only ventilation strategy, and a target ventilation rate of 50 CFM you would need to install a 50 CFM fan with an adjustable-speed DC motor for continuous operation.
Quick Answer. Trenches were built during World War I to protect stalemated troops on both sides from artillery and rifle fire. Although the war began with rapid movement of the German army, when the Allied forces stopped the Germans, both sides dug trenches to help avoid losing territory they had gained.
Trench: Drain field trenches effectively treat liquid flowing from the septic tank. A drainfield trench is generally 18 to 36 inches wide and up to 100 feet long.The trench contains a perforated pipe in a bed of 3/4-inch to 2-inch diameter rock covered by natural or synthetic permeable fibers.rench: Drain field trenches effectively treat liquid flowing from the septic tank. A drainfield trench is generally 18 to 36 inches wide and up to 100 feet long.