How Much do You Know about Drains?

How Much do You Know about Drains?

Many people in urban areas don’t think about where their water comes from. And they certainly don’t give much thought to where it ends up!

So, here’s a little refresher. Water comes into our homes via main water lines that connect to the city’s water supply. Tacoma’s water is stored in wellfields in South Tacoma and is supplied by primarily from groundwater and the Green River which is in turn supplied by snow runoff from the Cascade Mountain Range.

A massive underground plumbing system transports fresh water to homes across the city, and a separate one carries wastewater to nearby treatment plants. The picture gets much bigger when we think about what happens after that. It’s a neverending cycle, after all. But for now, we’ll focus on how drains in our home help keep water flowing in the right direction.

Proper drainage is critical to the safety and sanitation of your home and surrounding property. And contrary to a surprising number of assumptions, wastewater doesn’t just “go away”. What we put into our drains, be it toilet, sink, or floor, is merely part of a larger cycle. Let’s start with how many types of drains help to carry waste away to the right places.

Types of drains

There are two major types of drains in your average home: primary drains and secondary drains. Secondary drains are visible under sinks, floors, and behind walls. Secondary drains connect to primary drains, and primary drains connect to municipal sewer lines.

There’s also an important distinction to make between waste pipes and drainpipes. Waste pipes are specific to toilets whereas drain pipes carry greywater from sinks, appliances, showers, and bathtubs.

All of the drains in your house have a unique function:

  • Kitchen Sink
  • Bathroom Sink
  • Tub
  • Lateral Sewer Mainline
  • Drain Tile
  • Branch Drainage Lines
  • Soil Stack
  • Clean Out

Where do they all go?

Kitchen and bathroom drains carry greywater past the curved section of pipe under the sink called a “P Trap” and down to the lateral sewer mainline that carries waste away from of the house. Drain tile is a type of pipe made of corrugated plastic or clay meant for re-routing groundwater and rainwater to the storm sewer.

Branch drainage lines connect drains to soil stacks, and soil stacks move solid waste vertically to the lateral sewer line. The clean out is an access point for sewer cleaning. The sewer clean out is used by plumbers to access the main line easily without having to dig a trench. This is important when inspecting lines for damage or buildup that may be causing a backup in the house.

All of the primary and secondary drains in your house lead ultimately to the municipal sewer where it is then transported via a complex network of pipes to Tacoma’s water treatment plant. Drains may seem insignificant, but they play a major role in keeping contaminated water heading in the right direction. And with the help of things like vents and traps.

How traps, vents, and pitch support drainage systems

Traps are fitted inside drain pipes and work by creating a one-way-road of sorts; preventing wastewater and sewer gases from returning back to the house. Drain-waste-vent (DWV) lines also help keep fluids moving by allowing sewer exhaust to escape and air to flow in. The terminus of these types of vents can sometimes be seen on rooftops.

Finally, plumbing systems need a little help from gravity to maintain a downward flow. As a rule, plumbers install drainpipes at a slope of 1/4 inch per foot.

It’s an intricate process, which is why it demands the knowledge and skill of a licensed plumber. Call West Coast Plumbing, Pumps, & Filtration, LLC for expert drain cleaning, sewer cleaning, installations, and more.


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