How Plumbing Drains Work


The systems in your home are generally the same whether you have a sewer or septic system. Pressure is not a factor in drainage systems, as it is in supply systems. Instead, waste material exits your home due to the drainage pipes’ downward pitch, or slant, towards the sewer. The garbage is dragged along by gravity. This downward flow is continued by the sewer line to a sewage treatment plant or a septic tank.


While the system appears straightforward, it includes vents, traps, and cleanouts. The air might enter the drain pipes from the vents on the roof of your house. Wastewater would not flow properly if there was no air supply coming from the vents, and the water in the traps would have to be drained away.


Drainage systems are incomplete without traps. Every sink has a trap visible beneath it. Under a drain, it’s a curved or S-shaped piece of pipe. Water runs with enough power from the basin to pass through the trap and out the drainpipe, but enough water remains in the trap to form a seal that prevents sewer gas from backing up into your home. A trap is required in every fixture. Toilets are self-trapped, thus there is no need for a separate trap at the drain.


Drum traps are common in older bathtubs, and they not only establish a seal against sewer gas, but they also collect hair and dirt, preventing clogged drains. Drum traps, on the other hand, no longer meet contemporary code requirements. Grease traps are installed in certain kitchen sinks to collect grease that might otherwise clog the drain. Because grease and hair are the most common causes of drain blockages, traps commonly incorporate clean-out plugs that make removing or breaking up any obstruction easier.


A drainage system is commonly referred to as the DWV: drain-waste-vent system since it includes all of these components. All components of the DWV must be present and in good operating condition for water to flow freely and waste to depart properly. Examine the pipes in your basement or crawl space to gain a better understanding of the system.

Types Of Drainage Systems In Buildings

There are two types of drainage systems:

  1. Wastewater is collected from showers, sinks, kitchen sinks, washing machines, and other similar sources. Gray water is another name for this. Wastewater is usually drained through pipes with a minimum diameter of 75 mm.
  2. WCs and urinals are the sources of soil water or sewage. This is also referred to as “black water.” Wastewater is transported through pipes with a minimum diameter of 100 mm. Because soil water pipelines include sediments, they should be run horizontally at a steeper slope, such as 1:40. These can be made of either cast iron or PVC.

When draining waste from kitchens, a grease trap should be employed; grease should not be allowed to enter the conventional drainage system. A grease trap is essentially a miniature inspection chamber. The grease floats and must be manually removed on a daily basis. The inlets and outputs into this chamber should be arranged in such a way that the floating grease layer is not disturbed.


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