Concrete Sewer Pipe Strengths

Sanitary vs. Storm Sewer Pipes

• Concrete pipes deliver water for irrigation and water supply to homes and businesses and carry it away in sanitary and storm sewer lines. Concrete storm sewer pipes remove the excess water from heavy rains and irrigation around homes and businesses, dispersing the water in areas where it can be safely released. Concrete sanitary sewer pipes move liquid and other waste material form homes, businesses and industrial sites to the appropriate treatment plants where the water can be cleaned and released. In both cases, the pipes must be watertight, withstand the pressure of the dirt packed around them and resist erosion from the sewage contents.

Pipe Size

• Concrete pipes are manufactured in sizes ranging from 4 inches to 17 feet in diameter. The reinforced concrete pipe generally used for road culverts, storm sewers and sanitary sewers range in size from 1 to 12 feet in diameter. When using non-reinforced concrete, sewer pipes must be small, generally 6 to 10 inches in diameter. These pipes come in standard lengths of 8 feet.

The Concrete Mixture

• Concrete ingredients include Portland cement that contains calcium, silicon, aluminum iron and other trace elements, along with aggregate, consisting of gravel, pebbles or sand, and water. Combining water and Portland cement produces a chemical reaction called hydration that forms a mixture that's malleable when wet yet hardens into a rock-like material as it dries. The concrete's strength depends on the ratio of water to cement; the smaller the ratio, the stronger the concrete. Ideally, the concrete mix should contain 60 to 75 percent aggregate, 10 to 15 percent cement and 15 to 20 percent water. This ingredient ratio, along with proper mixing, molding and curing times and methods, creates the strongest concrete sewer pipes.

Sewer Pipe Strength

• The Army Corps of Engineers recommends using concrete pipes for sewers with an expected lifespan of 70 to 100 years, though many concrete pipes in existing sewer systems have exceeded this time frame. Concrete sewer pipe has a density, or compactness, ranging from 145 to 155 pounds per cubic foot, which adds to the concrete's durability. The compressive strength of concrete pipes can be fine-tuned by adjusting the wall thickness and the mixture ratio, reinforcing the concrete with steel and by burying the sewer pipes. In fact, the soil pressure doubles the load-carrying capacity of concrete pipes. Concrete sewer pipes are generally tested over a 28-day period to ensure they meet design strengths