Drain systems are a crucial part of your house and can be surprisingly complicated. There's a lot to understand when you think about it: the different types of pipes and how they work together.

What is a home drain system?

A home drain system helps to remove wastewater from your plumbing pipes. It consists of the following:

• The line that carries water to your house.
• Various household drains, such as sinks, tubs, toilets, and clothes washers.
• The main sewer line takes sewage (wastewater) to a treatment plant or septic tank.
  

How does a drain system work?

A drain system is simply pipes that carry wastewater from the fixtures in your house to a trap and then outside. This process includes gravity, venting, and pumping. In most cases, gravity moves water through the pipes with some assistance from venting or pumping. Gravity causes wastewater to flow downhill when it leaves a fixture higher than the trap. Venting occurs when air enters an enclosed pipe carrying water because of atmospheric pressure changes caused by weather events such as rainstorms or windy days. Pumping helps move wastewater uphill if there is little or no free-flowing drainage.

What are the main parts of a drain system?

A home drain system is made up of many parts, but it's essential to know the main ones so you can spot potential problems. The piping in your house carries wastewater from all of your fixtures and appliances out to the public sewer or septic tank. 

1. Fixture Drains - these are the visible drains you see in your sink, shower, and tub.
2. P-Trap - a curved pipe just after the drain to hold water and prevent sewer gases.
3. Toilet Trap - similar to a p-trap but in the toilet
4. Clothes Washer Stand Pipe - this is a specialty pipe to service the drain for your clothes washer.
5. Branch Drain Lines - these run horizontally with a slight downward slope taking water to the sewer line.
6. Soil Stack - branch drains flow into soil stacks.
7. Soil Stack Vent - will run from your soil stack and vent through your roof.
8. Sewer Line Clean-Out - mounted in the floor for access to your drainage system for emergencies 
9. Main Drain Line - this is the final drain line from your property to the sewer line.
10. Municipal Sewer Main - this line connects all the drain systems in your neighborhood and takes water to the treatment plant.

If you’re interested in learning more we recommend these websites:

School of PE

How Stuff Works - Plumbing

Larry o Plumbing