Biguanide was first developed as a presurgery antimicrobial scrub. It is the only nonhalogen sanitizer and oxidizer available for spas. (Both chlorine and bromine belong to the halogen family of chemicals.) Some spa owners prefer biguanide because it is less susceptible to UV rays than chlorine and bromine, it doesn’t require a stabilizer, it doesn’t degrade with high temperatures or changes in pH, and it usually is applied only every couple of weeks.
With biguanide, the water doesn’t smell of chlorine, of course, and it reduces the surface tension of water, which creates a smoother feel. And at recommended concentrations, biguanide won’t irritate the skin or eyes.
On the downside, biguanide is more costly than chlorine and bromine; it has a tendency to gum up filters; and it is incompatible with chlorine, bromine, copper-based chemicals
(such as certain algaecides), and nonchlorine shock (such as potassium monopersulfate).
Several companies offer complete biguanide spa care systems, which tell you exactly how to use each product. Follow the instructions carefully and you shouldn’t have any problems.
Testing Biguanide Levels. Biguanide levels are monitored with special test kits. To ensure proper use, follow the manufacturer’s testing and application guidelines precisely.
Adjusting Biguanide Levels. Biguanide is available in liquid form. The acronym for its chemical name is PHMB, which you may see on the package label. You’ll need to add biguanide to spa water only about every 10 to
14 days, but you should still test the water regularly to make sure it is balanced. Follow the manufacturer’s directions carefully to determine how much biguanide to add to your spa and how often. And always check with your biguanide dealer before adding supplemental chemicals to biguanide-treated water to make sure they are compatible.