This is a trap
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Why do I need it?
You need a trap because that is your protection against sewer gases coming into your house. The gases in
the sewers are so persistent that one of the reasons you have vent pipes coming out of your roof is to alleviate the
gases. If you smell a strange odor coming out of a drain you rarely use, it is probably because the water
in the trap has dried up and now there is no seal. The remedy is to put some water in the trap, by running water
into the drain.
You can see in Diagram A, where the water needs to be inside of a trap to create a proper seal that prohibits
gas to enter the house. Anywhere in between the horizontal lines in diagram A, will provide this function.
In Diagram B you can see
that the water is below the area that will create the seal. This area is known as the weir of the trap.
Darrel@plumbinglessons.com
You can see in Diagram A, where the water needs to be inside of a trap to create a proper seal that prohibits
gas to enter the house. Anywhere in between the horizontal lines in diagram A, will provide this function.