The following kitchen sink drain diagram illustrates problems with improperly constructed drain systems. Here, we see a kitchen sink drain with excessive bends and length to the line.

This kitchen sink drain diagram illustrates inefficient piping.

1.) Too many elbows
2.) Length of the drain line
3.) Inside diameter of the pipe for the application
4.) Poor venting

From the kitchen sink, downstream of the trap, the piping generally disappears into the wall behind the cabinet. The piping will run horizontally to a tee. From the tee, the pipe will become vertical. Gravity will lead water down from the branch of the tee. And, air will flow in from above the tee, through the sewer or plumbing vent.
Proper installation of the plumbing system will determine problems or efficiency in the use of the drain. In the diagram above, the vertical pipe from the tee leads down to a 90-degree bend. The pipe travels horizontally for a short distance and then drops from a second 90-degree bend. Following the drop, there is a third 90-degree bend then the pipe is horizontal until it runs over to the stack and meets a 45-degree bend, and then drops into the sewer.

The use of 90-degree bends should be avoided where possible. Limit to necessary use. And try to fit in long turn 90-degree bends where possible. What occurs is, that the grey water from the kitchen sink becomes vented when it drops through the branch of the tee. However, the ventilation is lost as soon as the wastewater piles in the 90-degree bend after dropping from the tee. From there, the grey water, levels out and is now vented from the air in the sewer. But, then there is a second horizontal drop where the water meets another 90 bend. The water will level off and then travel to the sewer.

You may be wondering why the 90-degree bends are a problem. The answer is, that the vent is choked off, and water stops flowing until the air inside the pipe can vent it. The wastewater may carry debris that will lodge itself in the bends of the pipe or imperfectly pitched pipe. Once this occurs, the build-up will become a restriction and then, eventually a blockage.

Use 45-degree bends to move the sewage through vertical to horizontal transitions where possible. This allows the vent line to be maintained. Also, determine the amount of volume that will pass from the sink. The standard for drains found in a home is based on a 1 1/4″ to 11/2″ drain from the fixture. Your drainage line should be 11/2″ to 2″ in diameter, depending on the use. Suppose you are piping a bathroom sink drain. In that case, you can reliably use an 11/2″ drain pipe to discharge water from the sink to the sewer. If you are piping a kitchen sink with more than one compartment, be sure to drain each compartment to an 11/2″ pipe then to a larger pipe when branching to the other compartments. This will allow airflow to continue when two compartments drain simultaneously.