Bacteria
Tap pipes contain water that stands still for long periods of time while the tap is off. Water remains inside the p-trap constantly as a back flow preventer, and it also does not drain completely from inside the pipes. Standing water breeds bacteria that often smells like a sewer. This problem is not serious but it needs attention. Bacteria can cause illness in humans if exposed for long periods of time.
Cleaning Tap Pipes
To remove bacteria, clean your tap pipes. Turn off the water supply to the tap as a precaution. Unscrew the p-trap and remove the fitting from the drain pipe. Wash out the pipe with clean water and scrub the inside with a pipe cleaner or similar cleaning object to remove all bacteria. Clean the drain pipe with the same tools, without removing the drain, which is permanently attached to your home's main drain line. Reassemble the p-trap and use the tap.
Sewer Back Ups
A sewer back up is not a common cause of sewer smells from the tap. Unless sewer water enters the home's main water line, the tap is not exposed to sewage and will not emit sewer odors. Even when the sewer backs up, there is no direct conduit for it to enter your home's water supply. So, sewage never enters the water main. The sewer pipe and incoming water lines are two separate pipes, and the two never connect. A connection would allow dangerous bacteria into your water supply.
Water Heaters
Your water heater may produce a rotten egg odor. This smell is similar to a sewer odor, and the two are often confused. The odor comes from the break down of iron particles in your water, especially in home's with well water. They tend to have more iron in the water than city water homes. There is a magnesium anode in your water heater to prevent corrosion of the tank. As this anode deteriorates, it feeds the bacteria that breaks apart iron particles and causes a sulfur smell in your tap. Increasing your water heater temperature to more than 140 degrees and removing the anode helps eliminate this bacteria.
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