Where Does Shower Water Go? Treatment and Reuse

When we take showers and use sinks and toilets in the home, the water seems to magically disappear and never bothers us again. If you’re wondering where it goes to and whether it’s wasted or recycled, you’d be glad to know that most of the water is recycled and made available for reuse. The treatment procedures are quite simple yet fascinating.

Shower water and water from sinks, toilets and other drains goes into the drainage system and ends up in a septic tank or wastewater treatment plant for cleaning. Septic systems clean water naturally then it seeps into the ground while water treatment plants clean it with chemicals ready for reuse. 

Where Does Shower Water Go?

Where does shower water go?

When shower water enters the shower drain, it combines with wastewater from the toilet and sinks then goes to either a septic tank or a wastewater treatment plant. If it goes to the septic tank, it will naturally get cleaned and allowed to seep into the ground. On the other hand, if it goes to the wastewater treatment plant (sewage treatment plant), it is cleaned by chemicals and machines then released back into the environment. 

The water from your shower goes into one of the following areas through the drainage system:

Septic tanks

Shower water goes into the septic tank where it’s naturally broken down by bacteria that make it clean enough to seep into the ground and be part of the natural water cycle. Water is cleaned in the septic tank in the following steps:

  1. Wastewater from the shower, toilets and sinks flows through the plumbing into the septic tank. 
  2. Anaerobic bacteria breaks down the organic material in the watery waste (effluent). 
  3. The byproducts of the anaerobic bacteria combines with inorganic solids to form sludge which will fall to the bottom of the septic tank
  4. Scum, made up of oils, greases and fats, will float to the top of the septic tank
  5. Solids are filtered from the outlet pipe which allows only the liquid part of the waste (effluent) into the drain field. The drain septic field is a large surface area which promotes bacterial activities and allows water to seep into the ground. 
  6. The drain septic field pipe allows effluent to seep into the gravel surrounding it which in turn allows effluent to seep into the soil around the septic tank. This gravel also allows oxygen to reach the bacteria in the septic tank. 
  7. Further aerobic decomposition of the wastes goes on in the soil and gravel surrounding the septic tank to further remove wastes from the remaining water. 
  8. The clean water then seeps into the ground and back into the natural water cycle. The drain septic field, also called the leach field, has holes through which water will be naturally absorbed by the soil. 

Onsite septic systems are very helpful since they work on their own without interventions or large maintenance costs (unlike wastewater treatment systems). However, unlike water treatment plants, the water from septic tanks isn’t clean enough for direct use that’s why it’s mostly released into the ground rather than piped back for immediate use. The EPA details several types of septic systems each with its own benefits and downsides.

You should empty your septic tank every 3 to 5 years although that depends on how many people rely on the septic tank. To avoid issues with your septic system, you should use septic friendly toilet paper that won’t clog up the system.

Water treatment plant (sewage treatment system/plant)

Once the water from your shower, toilets, and sinks reaches the water treatment plant, it’s treated then release back into the environment. The water treatment stages are as follows:

Where Does Shower Water Go?
  1. Primary treatment

Also called mechanical treatment, the first stage of wastewater treatment involves the removal of up to 60% of the suspended solid waste from the water. This includes human waste, cans, fruits, grease, gravel, sand, and many other objects. The removed solids are sent to a landfill or other favorable location. 

  • Secondly treatment

In the second stage, the remaining wastewater is broken down by aerobic bacteria with components such as food and human waste, soaps, and others being broken down. The same bacteria will form floc (blocks of waste) which are then removed from the treatment plant. 

  • Tertiary treatment

The tertiary stage involves filtering and disinfecting the water to make it suitable for release back into the environment. For example, phosphorus and nitrogen are removed from the water to avoid algae blooming in rivers, lakes, and everywhere the water will end up. 

This stage usually uses either ultraviolet (UV) light, ozone, or chlorine in the disinfecting process. Ozone and UV light are safer than chlorine since they’re not toxic to the environment. However, they’re quite costly.

  • Water release 

Finally, the water is released back into the environment either through natural water bodies like rivers and lakes or into the municipal water system for direct reuse. It can also be left to seep into the ground naturally. If you use incinerating toilets, you won’t have to deal with septic systems or water tretment plants for wter from the toilet since none is used.

Septic tank vs wastewater treatment plant

The main difference between septic tanks and wastewater treatment plants is that septic tanks simply separate the water from the wastewater while treatment plants treat it. All the differences include the following:

Septic tankWater treatment plant
No electricity requiredRequires a power supply like electricity
Separates the water from the wasteTreats the wastewater
The discharged water is not safe for useThe discharged water is safe for use
Little serving requiredRequires frequent servicing
AffordableCostly 
Has two major zonesHas three major zones

Where does the sewer water go?

Sewer water goes either back to the environment or is piped back into homes and businesses for rescue depending on how clean it is. Most sewer water from septic tanks will be channeled into natural water bodies or left to seep into the ground since it’s not clean enough for direct use. 

On the other hand, water from sewage treatment plants is often clean enough to be piped back into homes for use. Still, most of it it released back into the environment through rivers and lakes to be part of the natural water cycle. 

Does shower water and toilet water mix?

Shower water and toilet water mix once they reach the main drain pipe and into the sewer line. However, they have different drain pipes coming from each fixture with the shower having a drainpipe on the floor of the bathroom while toilets have drain pipes in the walls behind the toilet bowl. 

When you use the toilet and the shower, water from both fixtures enters their individual drain pipes then meets at the drain stack. This is a Y-shaped pipe with outlets on all sides. In our case, toilet water enters the pipe through one arm of the Y while shower water enters the pipe through the other arm. The Y can have as many branches as possible on the upper side. 

Water then meets at the lower part of the Y-shaped drain pipe which guides it to the sewer or septic tank through a (slightly sloped) horizontal pipe called the lateral connection, lateral line, or house lateral. Given that there are different setups to the sewage system of your home, you should ask your plumber exactly how it was down for your house to avoid issues. This also helps prevent clogging in toilets and showers. 

The drainage system of your house is vented through drain pipes that are connected to the sewage system to balance the air pressure between the roof and the outside. This way, excessive pressure, and sewer gases escape to the atmosphere (above your roof) instead of backing up into your home. The sewer gas backup is further prevented by P-traps installed in all drains, sinks, and toilets. Without proper venting, the toilet will have many issues including toilets not filling with water after flushing.

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