Biguanide (PHMB)
Another sanitizer for pools is biguanide, or PHMB. This compound has come to be known as a “non-chlorine” sanitizer, but perhaps would be more accurately called “non-halogen” since it does not rely on either bromine or chlorine. The PHMB system has created interest because it is said to be free of chlorine odors and irritation. Many people like the idea of getting away from the use of traditional sanitizers. While PHMB can be effective in controlling most microorganisms, the system is different from traditional sanitizers and has some drawbacks. For example, the system does not tolerate the addition of chlorine or bromine, and if added to a biguanide pool, these products can cause the formation of gummy deposits on surfaces and pipes. Since most source water contains chlorine as a treatment chemical, small amounts of the gummy deposits can form over time. On the positive side, the product is stable in the water and needs to be added only in top off doses every week or two and does not require the constant testing of levels as do chlorine or bromine. Absence of chlorine odors, reduced skin irritation and ease of maintenance are also claimed.