What is a Main Drain?


Your main drain is an integral plumbing system that removed all the waste water from your home. In essence all the drain pipes in a home connect below the house with the main drain, which then transports waste water into a septic tank or public sewer lines. As would be expected municipal codes are the determining factor when it comes to the distinct size of a main drain. For residential properties these pipe systems are usually required to be 4” in inside diameter. Additionally, local codes also specify the exact type pipe material used. However, the most common materials utilized include vitrified clay, plastic, cast iron, or even bitumized fiber. To prevent contamination, the main drain is usually located 10 feet away from the water supply line or 12” beneath it, if they happen to be in the same trench. The depth of such trenches is largely dependent on the climate of the given area as well as the exact location of the septic tank or public sewer lines.

To begin with a building’s plumbing system, for the most part, comprises of 4 main components.

What is the purpose of a main drain?

A main drain is an extremely important component of any residential plumbing system as it permits the effectual and safe removal of waste water from a home. This goes a long way in preventing the cropping up of serious health hazards as well as safeguarding the structural integrity of a house’s foundation.

How does a residential main drain work?

Each and every single plumbing fixture in a home has its own drain line that ultimately connects to the main drain. This has the task of transporting waste water to the septic tank or public sewer line. The main drain normally includes 2 components, which are the trap and vent.

The trap functions as an effective barrier that prevents waste water from finding its way back to the building. This fixture necessitates airtight and watertight connections utilizing a nut and ferrule. The main drain also features a network of vents (ventilation pipes) that ultimately protrude out of a home’s roof. The main purpose is to eliminate gaseous outflows from the sewer line that can drift out of the main drain into the living quarters. As a rule, main drains are installed adhering to a sloping angling criteria, which is known as the pitch, to facilitate for easy and steady waste water flow utilizing gravity. Ideally, this is usually a drop of ¼ inch per foot of the main drain.


It is thus self evident just how critical a main drain is to any household in the elimination of waste water and other filth. For this reason, it is highly recommended that homeowners take the time and resources to schedule regular maintenance on this plumbing system..