TECHNICAL BULLETIN

Rusty, brown, black, or yellow water appearing in the hot water.

Complaints of discolored water are commonly blamed on water heaters and storage tanks, but in fact, it is a rare occurrence for today’s high quality glass lined tanks to have a lining failure significant enough to allow water to contact enough bare metal to discolor the contents of even a small tank.

The most common cause of “rusty” water is a non-toxic iron reducing bacteria, scientifically termed Crenothrix, Leptothrix, and Gallionella. Iron bacteria is commonly found in soil, water wells, water treatment plants and water distribution piping systems where soluble iron exceeds 0.2 ppm, higher levels make conditions even more favorable. Soluble iron in the water provides food for the bacteria. Rusty discolored water is the end result of the bacteria feeding process. Water heaters and storage tanks usually require new anode rods as presence of iron bacteria contributes to premature anode failure.

The requirements for the bacteria to thrive are:

• Elevated levels of iron and manganese in the water
• Water with little or no dissolved oxygen
• Temperatures below 138°F

Items that can increase the potential for this bacteria are:

• Water softeners
• Well water
• Long periods of no water movement 

Since there is no simple way to correct pulsation of the water supply, removal of the heat traps is sometimes the only practical alternative. The heat traps may be removed from the heater without affecting the safe operation of the heater.