Tap water, though treated and deemed safe for human consumption, still contains a certain level of bacteria. These types of bacteria can usually be broken into one of just a few groups: iron bacteria, sulfur bacteria and coliform bacteria being the most common.
Iron Oxidizing Bacteria
Iron bacteria is considered the more plentiful of the two bacterial types, as there is a high amount of iron dissolved in tap water supplies. Iron bacteria are known as oxidizing agents because they combine iron with oxygen to form a rust-like slime that coats the inside of the pipes, screens, and can clog plumbing fixtures. This slime is not hazardous for human consumption, however, it is odorous and most people find its presence distasteful. This bacterial slurry can multiply at an astounding rate if the conditions are ripe for bacterial reproduction. Iron bacterial infections are characterized by rust colored water flowing from taps, rust colored stains in toilets, and foul smelling water running from taps, especially after long periods of non-use.
Sulfur Oxidizing Bacteria
Sulfur bacteria can be further broken down into two subspecies of bacteria: sulfur oxidizers and sulfur reducers. Sulfur oxidizers work much the same way as iron oxidizers, combining sulfur and oxygen to produce a slime coating that causes plumbing problems.
Sulfur Reducing Bacteria
Sulfur reducers work in an entirely different manner. Sulfur reducers are anaerobic bacteria that thrive in oxygen-depleted environments. These bacteria breakdown sulfur compounds and produce extremely foul smelling hydrogen sulfide gas. This type of bacteria is much more common than sulfur oxidizing bacteria. Symptoms of either sulfur bacterial infections include a “rotten egg” smell and a black slime coating, very similar to iron oxidizing bacteria.
In both cases, it is possible that the slime and/or smell that accompany the bacterial infections may only manifest when the hot water is run. This will indicate that the infection is occurring in the water heater. If the symptoms of infection only manifest when the toilet is flushed, then the toilet tank is probably the culprit. If the symptoms occur in nonspecific ways, the problem is more systemic.
Coliform bacteria are another species of bacteria that can infect drinking water. These types of bacteria occur naturally in the intestines of warm-blooded animals and are excreted in the feces. This bacteria type includes both disease and non-disease causing species. E. coli is one of the most well known coliform bacteria.