Household Waste Drainage Systems

1. Household Waste Drainage Systems

2. When we flush a toilet, empty a bath tub or sink, wash clothes, etc. we run water and waste through a system of pipes in our homes out to a waste system of some sort (we’ll look at this a little later). Drain pipes in our homes/buildings have to be the correct size. If they are too small they won’t permit waste to flow and if they are too large it becomes a problem when trying to install them and it doesn’t carry away the waste correctly.

3. From our sinks, toilets, etc. the waste runs into pipes. These pipes have to be at the correct angle in order for the waste and water to flow together. If it is too steep the water will leave the waste behind. If too low neither will run correctly. This will cause major problems in the system. The water and waste then move to a larger pipe called the soil stack. This pipe connects all the pipes and leads to the main pipe going from the building to the outside waste system. Inside the pipe system of the building there needs to be vents strategically placed. These vents allow air into the system so that the pipes can run correctly and also to vent the gases that build up from the septic waste. If these gases aren’t vented correctly they not only cause a bad odor but can be potential fatal or cause explosions.

4. Problems with vents A plugged vent can trap dangerous gases and inhibits drainage; similar to plugging a drinking straw with your thumb to hold liquid. Make sure the vent doesn't terminate in the attic. Trapped sewer gases can be dangerous, stink and cause serious structural problems. A system without a vent may actually suck water out of a sink's trap, or do the reverse and fill the sink with water when another fixture drains.

5. A trap blocks sewer/septic gases. Without one, sewer gases can flow up the stack, drain pipes and come out wherever there's a drain. A trap looks like a "U" and is installed below the drain. When water drains, the trap's shape causes a small amount of water to remain in the bend. That water blocks any gases from moving up the pipe and entering the room. NOTE: Traps are needed on all drains. That is, sinks, tubs, showers, washers, floor drains all need to have a trap in their drain lines. In most cases, a toilet has a built-in trap and doesn't require a trap in the drain line

6. In the pipeline there needs to be installed special areas: Cleanouts are put at different spots to allow access to the pipes if there is a blockage. These are Tees or Wyes placed in the system. Backwater valves are placed in the system as well. These valves do not let waste and water back into the system once it leaves the house/building. This has a one way flap the allows things to flow only one way. Backwater Valve

7. Waste Systems Once outside the home/building there are two main ways we get rid of human waste and water. Depending on where you live you will use one of these systems Municipal waste systems Septic Systems

8. Municipal Waste systems The overall state of Canada’s water quality is relatively high, but is increasingly being threatened by contaminants from waste systems near populated areas and industrial development. National Pollutant Release Inventory Domestic wastewater includes typical wastes from the kitchen, bathroom, and laundry, as well as any other wastes that people may accidentally or intentionally pour down the drain.

9. Treatment plant Many of the waste systems around our province dump the waste directly into the ocean. There are a series of pipes which come from houses, businesses, industry, etc. That feed into a much larger sewer trunk. These underground pipes then feed to a main area and all the waste water and run off water is dumped into different locations. Most of the waste water in the St. John’s Metro region goes directly into St. John’s harbour. The region is currently building a new sewage treatment plant so that all contaminants can be removed from the waste system prior to the water going to the ocean.

10. Private Treatment: The Septic Tank In rural areas where houses are spaced so far apart that a sewer system would be too expensive to install, people install their own, private sewage treatment plants. These are called septic tanks. A septic tank is simply a big concrete, plastic or steel tank that is buried in the yard. Wastewater flows into the tank at one end and leaves the tank at the other.

11. Anything that floats rises to the top and forms a layer known as the scum layer. Anything heavier than water sinks to form the sludge layer. In the middle is a fairly clear water layer. This body of water contains bacteria and chemicals like nitrogen and phosphorous that act as fertilizers, but it is largely free of solids.

12. As new water enters the tank, it displaces the water that's already there. This water flows out of the septic tank and into a drain field. A drain field is made of perforated pipes buried in trenches filled with gravel. A septic system is normally powered by nothing but gravity. Water flows down from the house to the tank, and down from the tank to the drain field. It is a completely passive system.

13. There are precautions to be taken with any waste and water system. This is especially true for a well and septic system. When planning your system you need to ensure that your septic system is far enough away from your well so that the run off from the septic field does not interfere with the well. This can have a deadly affect.

14. Activity:Using the book Modern Plumbing by Keith Blankenbakercomplete the following: Explain the various venting methods. P. 287 Why is selecting the right size pipe important in a DWV system? P.281 What are two main things that must be considered when designing a plumbing system? P.295 What is the difference between a Sanitary Tee and a Vent Tee? P.222 What is the difference between a Wye and a TY? P.222 A great resource for the description of the household plumbing system can be found at:http://www.easy2diy.com/cm/easy/diy_ht_index.asp?page_id=35720510