Dishwasher Spotting Problems

Hard Water

• Hard water is a regional problem that comes from too many minerals in tap water. It can result in calcium or other mineral deposits accumulating on taps or appliances. Spotting (calcium residue) on dishes and glasses is often another sign of hard water. Commercial water softening companies can attach softening tanks to your household water supply and provide soft water throughout the home. Once the water is softened, you should reduce the amount of detergent, as soft water does not remove detergent residue as well as hard water.

Too Much Detergent

• The common thought of "more is better" can prove counterproductive with a dishwasher. Filling the detergent bin to the top will often leave a portion undissolved in the cleaning process and result in residue. Reduce the detergent by 50 percent then run the machine and look for improvement. Continue to add a bit more until the spots return, and then go back to the last measurement.

Low Phosphates

• Phosphates in detergents have been linked to algae growth in lakes and reservoirs that deprive plant and marine life of oxygen. Detergent manufacturers have responded to environmental law and requests by reducing phosphate in their products. Unfortunately, the phosphate helps keep the dishes clean by suspending particles so they can't adhere to the dishes, as well as softens the water. Phosphate levels in the past that have been as high as 8.5 percent are now often found at .05 percent.

Clogged Filter

• Most dishwashers have a filter located on the bottom below the rack near the back of the unit. This filter can become clogged with detergent, creating spotting or a thick film on dishes or glasses. Remove and clean the filter, pour a cup of white wine vinegar in the bottom of the unit and run the system (empty and without detergent) on the longest and hottest temperature. Stop the unit before the drying cycle and hand-dry the walls and racks of the unit.

Commercial Solutions

• Several commercial additives are very successful in preventing dish spotting. Most are additives that accompany the detergent in the system and most have a citrus base due to their use of citric acid. Rinsing agents help keep spots away by lowering the surface tension of water, keeping it from staying on the dishes or glasses in the drying process.

Home Remedies

• Citric acid is often suggested as an additive to clean lime scale. Purchased as sour salt or sodium citrate, citric acid acts as a water softener, helping to remove unwanted metal ions that cause spotting. A popular home remedy is to use an unsweetened package of powdered lemonade with the application of detergent. Using a quarter cup of lemon juice is another choice but could be more expensive. While weaker than citric acid, white wine vinegar poured into the bottom of the machine will yield some results, but not better than what is achievable with citric acid.