Is there any effect of high water pH in a laundry wash process?

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Written by Rich Fitzmorris

Question: Is there any effect of high water pH in a laundry wash process? Our normal water supply pH is 7-8, but I recently encountered a pH of 9. What might cause this? Is it safe to increase sour to maintain a final linen pH of 6-7, or should I stick to the rule that final pH should be one less than the water supply pH?

Answer: Before making any changes I recommend verifying that the water has indeed changed. Check the pH meter against a standard buffer, and have a chemical technician look into this further.
Washing and bleaching steps are generally unaffected if the incoming water pH is somewhat high. However, rinsing and sour baths can be affected. When titrations of the wash formulas are taken, be certain that total alkalinity is being reduced properly. When using an alkaline base chemical system, the last rinse should be titrated to less than 50 parts per million of active alkalinity.

The cause of higher than normal fresh water pH would be at the source of the water. The local water treatment plant often has to make adjustments if they switch from one source of water to another. Perhaps the treatment plant is trying to control the quality of the water by having a high pH during a time of prolonged high temperature weather conditions. If you still have concerns about the incoming fresh water quality, I suggest contacting the local water utility service.

The pH of the incoming water generally has nothing to do with what the final pH of the textiles you are washing should be. The finishing pH is what is important for fabric quality and comfort. There is no rule that says you should be only one pH scale less than the water. It might be that you would not have any problem depending upon what the textile is, however the pH of our skin is approximately 5.5. Therefore, when items that are worn have a significantly higher pH, they could become a possible irritant. I recommend dropping the pH to the acceptable levels of the past, and continue to investigate why the source of water has experienced a change in pH.