Have you ever experienced the terrible smell that can come from a bathroom that has a failed p-trap? If you haven’t, you are fortunate, because the gas does not just have a terrible odor, it is also harmful to your health, especially with long term exposure. This is why you will find a p-trap installed on all the drains in your home. Sometimes, however, p-traps fail. There are a few different reasons why this could happen. For example, if you have more than 2 sources of water draining through the same p-trap, this could overload the p-trap and cause it to malfunction.
There is also the possibility that a sink that isn’t used for a long time has a p-trap where the water evaporates over time, causing sewer gas to escape. There is a device called a tap primer that will automatically top off the p-trap when it gets low, so if you have a problem with this, it is a worthwhile investment.