When you hear about vent pipes and traps do you know what they are all about? Its good to have a general idea when caring for a home.
Getting water to the appliances and plumbing fixtures is only one half of the home plumbing system. The other half is removing the waste water. This is called the DWV system or Drain, Waste, and Vent system. This consists of a network of pipes that carries the waste out of the house to the municipal sewer line and sewer gases to the out doors.
Waste pipes have to be wider diameter then supply pipes so as to remove solids as well as liquids.
Waste pipes are slopped to enable flow by gravity as oppose to pressure.
The DWV system has a means of preventing sewer gasses from flowing back into the house
Waste pipes are mostly seen as black plastic pipe, cast iron or galvanized pipe.
Every plumbing fixture in a house has what is called a “Trap”. The purpose of the trap is to prevent sewer gas from flowing back into the house. If you look under your sink, lavatory, tub, etc. you will see a “U” shaped pipe which retains water in it. These traps not only seal, they keep the foul gasses from entering your home and also keep rodents from entering the house by way of the sewer pipes. These traps work well as long as they are full of water.
Each plumbing fixture is also vented, meaning the fixture is connected to a pipe which goes up through the roof allowing sewer gases to escape to the out doors. This vent pipe also prevents water from being siphoned from the “Traps”.
Dave Silva/GC
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