Reasons for a poor wash result in Commercial Dishwashers and Glasswashers

Many people complain about the quality of the wash result from their dishwasher and the amount of rewash required in their establishment. In a most cases, the poor results can be attributed to one of 4 issues:

Poor preparation of the ware (poor scrape down or pre-rinse)

* For most Commercial Dishwashers, scrape down and pre rinse is critical. A commercial dishwasher is not a food waste disposal system. Removing all hard solids from the ware will reduce contamination of the wash tank. A heavily contaminated wash tank can reduce the effectiveness of chemicals, reduce wash tank temperature, and may leave a residue on the ware. Some rack conveyor and flight type dishwashers come with a prewash section which can handle heavy soils, removing them before they hit the wash tank.

Chemical imbalance

*Chemical is an integral part of the wash process, but it is not THE critical part of the wash process. The common tendency is to add more chemical to the tank for better performance. Unfortunately this may cause more problems. Excess detergent may cause foaming in the wash tank. This foaming may reduce volume and pressure running through the wash pump. This excess chemical may also be difficult for the final rinse to remove, leaving a residue on the ware. Excess chemical may also cause damage to the heating elements within the wash tank. This may cause the unit to struggle to maintain temperature, increasing energy use and reducing the life of the element. This is far from ideal as THE most critical part of the wash process is TEMPERATURE. For every degree above 60 that the wash water is, there is roughly a 10% increase in chemical efficiency. This negates the need for more chemicals to be added.

Poor machine hygiene

* It's a simple question: How can a machine clean if it is dirty? Yet many establishments neglect their dishwashers or have older, poorly designed units that are hard to clean. The ideal machine would have a one piece pressed metal tank, easy to remove strainer pan(s), and cover corners to aid in cleaning. Regular descaling or hygiene cycles (a standard feature in better quality equipment) will aid in this task.

Machine related issues.

* As we discussed earlier, temperature is a critical part of the wash process. Many older machines which use an overflow system in their wash tanks may struggle to maintain temperature as the hottest water at the top of the wash tank is what is being dumped through the overflow. Also, many machines loose a lot of heat energy through bad design. Three sided gods on pass through dishwashers are the best example of this. At the end of a cycle, the hood is opened. Having a three sided hood (no back panel) allows the steam to escape rendering the wash chamber cold. When the next cycle starts, energy is lost out of the hot wash water into the chamber. Switching to a machine with a 4 sided hood design will capture 70% of steam energy within the wash chamber, keeping the wash water temperature up and saving 30% energy on heating the wash tank. Poor wash nozzle design may also contribute to a poor wash result. The unit may be pumping a high volume of water, but if the power of that water is not being directed correctly, it is  of no use.

When looking to replace your dishwasher or glass washer, these are wall factors which need to be considered. As always, if you have any questions relating to dishwashers, glass washers or any other piece of equipment, please feel free to contact me at any time.