Q: We are getting water spots after using an alkaline wash and acidic rinse in CIP cleaning. Why is this happening?
A: A two-step cycle with a base followed by an acid, whether it be CIP cleaning or in a large scale liquid dispensing system washer, is a robust and, when needed, is a recommended process. Water spots typically occur because of two main mechanisms:
1. If any items being washed have a shape that can retain dirty wash water, that water may get carried into the rinse cycle, spread over the items being washed. They then and dry and form water spots. To solve this, load the items in a way so they drain completely and do not risk carrying dirty wash water into the rinse cycle.
2. Washing with hard tap water (high in calcium, magnesium and iron) along with underdosing the detergent, may mean there is not enough chelating agent to tie up the hardness ions. When this occurs, these ions will not rinse easily and can lead to water spots.
Using an alkaline wash like SolujetⓇ Low Foaming Phosphate Free Detergent followed by an acid rinse, like CitrajetⓇ Low Foaming Acid Cleaner, can help solve this problem. Be sure to use at least a 1% Solujet wash solution (10 mL/L)and 1% Citrajet rinse solution (10 mL/L). Higher concentrations give better capacity, and can be quite useful for higher dirt load applications. It doesn’t do a significant amount for cleaning ability but can be vital for highly adherent resides found in some biopharma and cosmetic applications.
Avoiding rinses, especially final rinses, with hard tap water also helps eliminate water spots. Use deionized, RO, or distilled water for rinsing (and even washing – though not necessary) to avoid this problem.
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