Drainage,
Wastewater, and Vent Systems Unlike the supply system, which uses pressure to deliver water throughout the house, the drainage system depends on gravity to take wastewater away. All of the water used in the sinks, toilets, and tubs throughout the house must flow down to the sewer or septic line in the basement via a network of increasingly larger drainpipes. This system is called the drainage, waste, and vent (DWV) system. Larger pipes allow water to drain quickly.
The larger the diameter of the drain pipe, the more water it can handle.
In fact, drainpipes are even larger than supply pipes. But its not just
because they handle water: Waste disposal also requires space for air
and gas buildup, too. |
|
|||||||
|
Traps
and Sewer Gas
Waste deposited into the sewer line decomposes, producing noxious gases. Traps prevent these gases from backing up and being released into your house. A trap typically is a U-shaped bend of pipe that traps a small amount of water inside it every time you use the appliance. The trapped water acts as a barrier between your house and the sewer gas inside the drain network. Every plumbed appliance in your home is required by law to have a trap. Sink traps are easy to spot; toilet traps are contained within the toilet, and are less obvious. Although these traps are very effective barriers, the sewer gas pressure building up inside the drains would eventually overcome them if the system were not vented. Venting the System Vents also allow air to enter the system
for without air the wastewater would not be able to flow out. Think of
a gas can or juice can: The liquid inside cannot flow out unless a vent
hole is opened to allow air in to keep it flowing. Your home vent |
|||||||
system works by the same principle. For wastewater to move freely through the network of drainpipes and out to the sewer, there must be a way for air to get into the system. Otherwise, the drains would empty slowly, if at all. In fact, adequate venting is so important that a partially blocked roof vent can slow your drains to a standstill. Water moving through a drainpipe also displaces air that's already in the pipe. If the air has no place to go it will cause a pressure bubble inside the pipe. This pressure buildup will stop additional drain water from entering the pipe. Venting the pipe allows the pressure from the displaced air to escape, again keeping it all flowing. DWV System Design The Waste Stack The Roof Vent Vent pipes from lower floors must join the roof vent above the upper floor appliances to avoid backups in the system. Unlike drainpipes, vent pipes can run horizontally since gas-air pressure is drawn upward by the lower atmospheric pressure outside the house. |
||||||||
All
About Dol | What's New | Contact
| Sitemap | Link
Copyright Sudprasert Engineering (C)2002
10 February, 2003