How Does Sink Odor Occur?

The most common way a p-trap can dry out is from evaporation as a result of inactivity.  There are a number of other ways a p-trap can lose water including improper ventilation, wind oscillation, capillary action, and siphoning.  With a P Trap Pal installed, sewer gas will not enter your home even when your p-trap has dried out!