Know Your House Drainage System

Elements You Absolutely Must Know When Remodeling

Home drainage... Who cares? Uh oh, now the toilet won't flush, kitchen sink is full of gray water, and the downstairs tub is brimming with human waste.

It's funny how your home's hidden infrastructure--in this case, gray and wastewater drainage--becomes suddenly fascinating when it's not working. It's best to know about drainage when remodeling so that you don't have expensive troubles later on.

Let's look at your house's drainage system, properly called DWV, for...MORE Drain-Waste-Venting, from the moment water or waste enters a drain to the moment it enters the municipal line:

  • 01 of 08

    Sink, Shower, and Tub Drains

    picture of tub drain removed
    Tub Drain Removed. © Lee Wallender; Licensed to

    The upper section of the drain for tubs, showers, and sinks is the part that everyone is familiar with. In most cases, if you're having drainage problems, the solution is not to be found in this area. You'll either need to go down to the P-trap or farther down in the drainage area. Sink P-traps can be accessed below the sink and cleared out. Tub and shower traps cannot be accessed and thus must be snaked out with a drain auger.

  • 02 of 08

    Washer Drainage

    Washer Drainage Line
    Washer Drainage Line. © Lee Wallender; Licensed to

    I've split off your washer drainage system from sink/shower/tub drains because it's sometimes hidden behind walls.

  • 03 of 08

    Branch Drainage Lines

    Branch Drainage Line
    Branch Drainage Line. © Lee Wallender; Licensed to

    Branch drainage lines connect drains to soil stacks. They are often completely hidden by ceiling wallboard.

  • 04 of 08

    Soil Stack

    Solid particles move vertically down this pipe to the lateral sewer line.

    Continue to 5 of 8 below.
  • 05 of 08

    Soil Stack Vent

    This is the "V" of DWV, and the only part of this system that does not carry water. This pipe runs vertically upward, performing two functions: 1.) Carrying noxious fumes away; 2.) Providing a release so that discharge waste and soil can move downward (much like piercing two holes in a can will allow the liquid to exit faster and easier). Whenever you see a mysterious pipe sticking up from your roofline, it may be the soil stack vent.

  • 06 of 08

    Sewer Line Clean Out

    Sewer Line Clean Out
    Sewer Line Clean Out. © Lee Wallender; Licensed to

    The sewer clean-out is only there for emergencies and regular cleaning. It allows an auger to move freely through your lateral sewer main.

  • 07 of 08
    types of sewer pipe
    Sewer Main - 3 Types of Pipe. © Lee Wallender; Licensed to

    All wastewater from your house is carried to the municipal sewer line by one pipe. Usually 4 inches in diameter, this pipe might be either ABS or PVC plastic, clay, or cast-iron. In some cases, previous owners may have patched together all three types of pipe.

    Read: Sewer Main FAQs

  • 08 of 08

    Municipal Sewer Line

    Municipal Sewer Line
    Municipal Sewer Line. © Lee Wallender; Licensed to

    The end point of your home's drainage system is the municipal sewer main. Your lateral line will run perpendicular into the main, angled downward to promote flow of waste. You have no control over the municipal line, since it is owned by a city, county, or wastewater district.