Originally developed as a pre-surgery anti-microbial scrub, PHMB was patented in 1977, and marketed for pools and spas under the trade name Baquacil. This technology has the distinction and the EPA approval as the only non-halogen sanitizer available for pools and spas. Biguanides, as the class of chemicals is called, is chemically known as polyhexamethylene biguanide. You may have heard of using peroxide to bleach your hair or for an ear infection. The formulation is a bit different, but basically in the same chemical family.

Here's a page if you're looking here to find out how to convert back to chlorine or some other sanitizer from a Biguanide treatment.

When the patent expired back in the 90's, Bio Lab introduced a line of biguanide products under the name Soft Swim. Since then, other chemical manufacturers have produced their own line of biguanide based pool care products, including Revacil, Splashes and most recently Aqua Silk.

A full system for complete halogen free water care, biguanides are also the only stand alone alternative to traditional sanitation methods [chlorine]. The Biguanide itself is combined with algaecides and hydrogen peroxide for periodic oxidation.

Biguanides will gum up pool filters, and filter cleaning products are available to de-gum it. DE or cartridge filters are not recommended by manufacturers, who suggest sand filtration, being easier to clean, although they recommend changing the filter sand every two years. If you have a DE filter, it is recommended that the filter be taken apart and hosed clean after each backwash, to ensure a thorough cleaning. Use of their filter cleaning products is recommended twice per season, to combat the slimy gunk that accumulates, and always before closing a pool for winter.

Testing for levels of biguanide in the pool can be accomplished by the use of test strips, which may not be very accurate. Baquacil recommends taking a water sample to your Baquacil dealer once per month, or after a heavy rain, or adding large amounts of make-up water.

Don't add any other chemicals but those recommended by the manufacturer - adding a small amount of chlorine and your pool can turn to orange sherbet! I find it odd that at least one manufacturer recommends that biguanide treated pools be closed with chlorine – after allowing the PHMB levels to drop to zero, they suggest using Trichlor tablets and chlorine shock for winterizing. The reason given for this is that biofilms can form in the pipes and cause resistant algae that PHMB cannot remove.

Biguanides are also incompatible with TSP, ozone, detergents, ionizers, and other common chemicals, but are not at odds with any water balancing chemicals you may add to adjust pH, Alkalinity or Calcium. When unsure of compatibility, contact your dealer before adding any non-system chemical to the pool or filter.

Some fish pond experts use the hydrogen peroxide shock to control algae in Koi ponds and other natural bodies of water. Those who do so may be taking a large risk of killing or sickening expensive ornamental fish, but some experts find it useful for summer algae blooms. Do your homework if you plan to add pool chemicals to a pond, especially a fish pond. Manufacturers do not recommend this use of peroxide.

Users of PHMB can have trouble with pink slime and white mold, which are both forms of bacteria, not algae. According to the manufacturer or Revacil, a French PHMB product, both pink slime and white water mold occur when the pH level drifts too high, and the biguanide (which is actually a bactericide) drops too low. Balancing the water, raising the biguanide level to around 50 ppm, and shocking the pool with hydrogen peroxide is the recommended treatment.

Cloudy water is also a problem for many biguanide users. If biguanide levels and pool water balance is good, the most likely cause is poor filtration, possibly a combination of a gummed-up filter, and not operating the filter long enough each day. There is a flocculant available from your dealer which will settle suspended particles to the floor, for vacuuming to waste (using the waste setting on a multiport valve).

Biguanides have been reported by users to be easier to use, with less chemical level testing, and less adding of chemicals. The water doesn't smell of chlorine of course, and the reduced surface tension gives the pool water a smoother feel. Biguanides don't degrade with sunlight, temperature, or changes in pH levels like chlorine. At recommended concentrations, biguanides won't irritate the skin or eyes and can't corrode pool equipment. And, no, at recommended levels, using hydrogen peroxide based pool sanitizers will not turn your hair platinum blonde!

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