What is a Drain-Waste-Vent (DWV) System?
Do you know how plumbing works? While it may seem like magic since nearly everything happens out of sight, these inner mysteries have simple and elegant explanations.
Let’s start with the main water-supply-drain-waste-vent system. The water supply system brings hot and cold water into the home and the drain-waste-vent (DWV) system drains water and waste from the building to a local sewer or septic tank.
Water Supply System
Water enters your home via the main supply line, which can come from a private well or the city. If you have municipal water, this pipe — the main supply line — passes through the water meter before entering the home. The meter registers the amount of water used.
After the main supply line enters the home, a branch line splits off and runs to the water heater, which supplies hot water to fixtures and appliances in the house.
The main supply line provides water to fixtures and appliances, which are controlled with valves and faucets. Unlike the drain system, the water supply system is pressurized, usually around 40 to 55 psi. The supply system has to be pressurized because supply water runs up; wastewater is able to run down naturally with gravity.
You may hear pipes banging when you turn off a faucet. This is called a “water hammer” and should be fixed before any damage is caused. A plumber will install air chambers or mechanical water hammer arresters to trap the air and cushion the impact the hydraulic shock.
Drain-Waste-Vent (DWV) System
The drain-waste-vent system, also known as the sanitary system, is all of the plumbing in your home minus the water supply system. This includes the drainpipes, drains, and vents. When wastewater enters the drain system, it has to flow past the drain trap—a U- or P-shaped piece of pipe that creates a water seal to prevent sewer gases from entering the home. Every drain in your home should have a goosenecked P-trap.
The drainpipes send water to the main sewer line, located underground. The main sewer line sends water to the municipal sewer system or septic tank, if you have one.
The drainpipes are attached to a system of vent pipes, which bring fresh air to the drain system. This helps prevent suction that could slow or stop drain water from flowing freely. The vent pipes usually exit the home via a roof vent.
Wastewater ends up in the main waste and vent stack, which curves to become the main sewer line that exits the house near the foundation. If you are connected to a municipal system, the sewer line connects with the main sewer line located near the front curb. If there is no sewer service available, the sewage would empty into a septic system.
The DWV system is one of the most important and complicated systems in the home. Contractors usually install it first and plumbing codes help ensure proper safety and sanitation. Strict regulations, such as pipe size, slope, and fixture height, must be followed to keep contaminants out of the house.
If you have any questions about your plumbing system, don’t hesitate to contact Sobieski Services. We provide comprehensive HVAC and plumbing services throughout Delaware, Maryland, Pennsylvania, and New Jersey.