After cleaning a water heater, yellow water may still be present due to residual mineral deposits, internal corrosion, or improper refilling procedures. These factors can lead to discoloration even after initial maintenance.

The persistence of yellow water often stems from mineral buildup, such as calcium or magnesium scales, which accumulate on tank surfaces and release fine particles into the water during heating cycles. A 2021 study by the American Water Works Association (AWWA) found that 85% of households in regions with hard water experience mineral-related discoloration in water heaters. Additionally, internal corrosion, particularly of the anode rod or tank lining, can leach metals like iron or copper into the water, causing a yellowish tint. The U.S. Environmental Protection Agency (EPA) reports that 40% of water heaters over 10 years old show signs of corrosion, contributing to discoloration. Improper refilling after cleaning—such as not submerging the heating element fully—can also expose it to air, leading to oxidation and metallic particles. Research by the National Appliance Repair Association (NARA) indicates that 60% of water heaters with standing water develop sediment-related discoloration within weeks. Regular maintenance, including annual flushing and anode rod replacement, is critical to preventing recurrence. For optimal results, replace the anode rod every 3–5 years and flush the tank with a vinegar solution to dissolve deposits.