Understanding how your plumbing system works is an essential part of homeownership. When you know how the plumbing in your home functions, you have a better grasp on how to take care of it and how to prevent a multitude of costly problems.

Below, we’ll provide a high-level explanation of your plumbing and explain the main components of its water supply system and drain-waste system.


In broad terms, your plumbing is made of two systems:

  1. The water supply system brings water into your home for use (washing dishes, taking showers, flushing the toilet, etc.).
  2. The drain-waste system transports wastewater and sewage away from your home.

These two systems are comprised of pipes. Your home’s water heater, faucets, sinks, showers, bathtubs, and toilets are also part of your home’s plumbing.


The Water Main

How does water get to your water supply system? Unless you’re living “off the grid,” you get treated water from a local company. The company delivers water to your neighborhood through a huge pipe called a main. From there, it flows to your home as needed, with a meter tracking your water usage so that the company knows how much to bill you.

The Main Shutoff Valve

Most homes have a main shutoff valve near the meter. When you turn the handle clockwise, the valve will stop the main from supplying your home with water. Familiarize yourself with the valve’s location and how to use it ahead of time: you may need to turn the water off in a hurry if you spot a sudden leak in your home.

The Supply Line

After water reaches your home’s water main, pressure pushes it into your supply line (a pipe that is frequently made of copper, plastic, or galvanized iron). Water then travels through the supply line to your home. Right before it hits the water heater, the supply line splits into a cold service line and a hot service line. Water in the hot service line enters your water heater, while water in the cold service line continues toward wherever it’s needed.

Hot and Cold Water

Once heated, hot water leaves the water heater and enters the hot service line alongside the cold service line. Then, these primary pipes branch off into a network of service lines. These lines bring water to intake pipes, which are connected to water-using appliances and faucets. When you turn the faucet handle, you’re opening a valve that lets water out of an intake pipe.


As mentioned earlier, the drain-waste system takes wastewater and sewage out of your home to the municipal sewer. Wastewater is any water that ends up down a drain. While the water supply system moves water based on pressure, the drain-waste system moves waste based on gravity.


Under kitchen or bathroom plumbing fixtures, plumbers install “traps” through which wastewater passes. These traps work with standing water and gravity to keep the wastewater, sewage, and sewer gases from backing up and causing a smelly disaster.

Toilets contain built-in traps, whereas bathtubs will often have drum traps to help prevent clogged drains. Sinks require P-traps, named for the P-shaped curve of the pipe that creates the “trap.” You probably see a P-trap in your home whenever you open the cupboard under a sink.

Drain-Waste-Vent Lines

In most cases, the next place wastewater ends up is a drainpipe. In the case of wastewater from a toilet, the water and sewage will enter waste pipes, specifically, which tend to be wider than drainpipes because of the material they need to transport.
To keep things moving, these pipes are connected to vent pipes. Vent pipes give sewer gases a place to go, and they prevent suction from occurring inside your plumbing system, which, in turn, would stop wastewater from flowing.

Sewer Line

All of your drain and waste pipes eventually empty into a main drain, often called the sewer line or main sewer line. Your home’s sewer line is what transports all the wastewater away from your home and takes it to the municipal sewer. The line is usually only four to six inches in diameter and is built at a downward angle to keep wastewater flowing out.


Now that you have some basic information about your home’s water supply system and drain-waste system, it’s easier to understand how critical it is to take good care of them.
When it comes to your water supply system, keep an eye out for these signs of an issue:

  • Discolored water or water that doesn’t taste or smell right: this could mean that something has infiltrated your main water supply line.
  • Recurring leaks or banging/knocking noises coming from your plumbing: this usually means that your water pressure is too high.

When it comes to your drain-waste system, watch out for these red flags:

  • A slow drain: this means that a clog is developing, either from a large obstruction or a buildup of material.
  • Soggy or especially lush, green patches of grass in your lawn: this a major red flag that means you probably have a leaking sewer line.
  • Sewage odors: this could indicate that one of the traps in your plumbing is not working correctly or that you have a sewer line issue.
  • Gurgling in a sink drain: this often signals that a clog is developing, but it could also mean that something is blocking a vent pipe.

If you need plumbing services in Woodland Hills, San Fernando Valley, or the Greater Los Angeles Area, Contact Bryco Plumbing at (818) 805-0883 or online!