Plumbing might seem like a fairly simple matter, but there are some things that make it complicated. One of these things is sewer gas.
Because of the mixture that goes down the drain, sewer gas is formed, and it is not just foul smelling, it can actually be very harmful to your health. This is why p-traps play an integral role in your plumbing system. A p-trap will let things pass through to the sewer, but it blocks the gas from coming back up. However, it is possible for a p-trap to fail and let these gasses through. For example, if you have a sink that isn’t used very often, the water in the p-trap could evaporate and break the seal that it used to form in the pipe. To counteract this, you could either set a schedule for yourself when you turn on the faucet for a short while in seldom used sinks, or you could install a tap-primer that will add water to the p-trap when it runs low.