Waterline Accumulation – Biguanide Systems

Formation of deposits along the waterline is sometimes seen in Biguanide treated spas. There are a couple of different types and causes of waterline accumulations.

One type of waterline formation is light or fluffy and easily removed with a sponge or cloth. High pH or excess amounts of a Biguanide sanitizer cause this type of waterline formation. This formation is common at start-up due to miscalculation of the spa volume, which results in an over-dosage of sanitizer.

Another type of waterline formation is a sticky, dark brown or green deposit. This type of waterline formation is very difficult to remove. Use a surface cleaner for spas to remove this buildup. Some waterline accumulation at startup is common. Continue using all Biguanide products as directed.

The proper application of Biguanide products and the proper maintenance of pH in the 7.2 to 7.6 range can prevent waterline accumulations. The accumulation of deposits at the waterline is closely linked to a high pH. Biguanide treated spas will experience waterline accumulation at a pH greater than 7.8. It is important to remember that a spa’s pH will tend to drift upwards due to elevated water temperature and aeration of the water during jet or blower operation. Test the pH regularly and adjust with pH Decreaser as needed.

Note: This information is intended for a residential spa with average use. It is not designed for public, commercial, or semi-public spas. If your hot tub is used more than three times per week, you should check and make chemical additions more often than suggested.