Biguanides were originally developed as a surgery scrub disinfectant.  

Chlorine and Bromine are considered halogens because they form a negative ion and are in group VII of the periodic chart.  Biguanide is a NON-halogen.  The chemical name is guanylguanidine [C2, H7 N5].   PolyHexaMethylene Biguanide also referred to as Polymeric Biguanide or simply PHMB is available under the trade names Baquacil TM, BaquaSpa TM and SoftSwim TM.  .  

It is the only non-halogen approved by the EPA for sanitizing, but it is not recommended by the National Pool and Spa Institute (NSPI) for use in spas and most swimming pools.  It is NOT an oxidizer, so it will not break down body oils, waste and perspiration.

Biguanide is generally used in conjunction with algaecides and hydrogen peroxide for shocking.  According to the users, the overall cost of maintenance is higher with Biguanides than with Chlorine.

Biguanide is not compatible with other pool chemicals that contain chlorine, bromine, iodine, silver, copper or persulfate.  It is also not compatible with other household chemicals such as detergents, cleaners, etc.  READ THE LABEL CAREFULLY!

We have had reports of Biguanides gumming up pool equipment especially DE and cartridge filters.  People have said that sand filters gum up the LEAST with Biguanides but you MUST clean them every 3 or 4 weeks.  This is in ADDITION to backwashing.

They are also known to cause a scum ring around pools and lots of foaming in spas.

To counter these drawbacks, the manufacturers also sell a wide selection of special additives such as filter cleaners, anti-foamers, anti-scum ring cleaners, algaecides, etc.

Most Biguanide systems include 7 special chemicals for start up and routine maintenance:

1.) Biguanide Solution to maintain 20 to 60 PPM (manufacturers disagree on the ranges)

2.) An Algaecide to be used weekly.  (Seems to be some disagreement among the manufacturers as to whether Quats or PolyQuats are compatible.)

3.) Hydrogen Peroxide shock to be used monthly or as needed to maintain 20 to 60 PPM (manufacturers disagree on the ranges)

4.) A defoamer to be used as needed

5.) A poolside scum cleaner to be used as needed

6.) A filter cleaner to be used about every 2 months

7. A filter aid (flocculant)

We have seen lots of negative comments about Biguanides for one reason or another.  We have also seen lots of web pages dedicated to detailing the steps to converting from Biguanides back to chlorine.  Not sure if it's their misuse or what.  For these reasons, we are skeptical of their use in pools and spas.  

For what it's worth, here are a few quotes:

"I have been one of those people posting problems with Baquacil. I was anxious to read your post hoping that it would tell me some new information that would tell me what I did wrong for 3 years even though I have now switched to chlorine. I am sorry to say that I followed all your instructions for 3 seasons (which were also explained to me by my pool pro) and I had nothing but problems every year. Now of course I have only been using the Nature2 and chlorine for a little more than a month and I cannot say if I will have problems or not this season, BUT I can say 2 things that I do know for sure. 1. I spent one third the money on chemicals for this season than I would have just on the normal BAQ system. This amount does not include any of the "special" chemicals I needed to solve problems....which might I add never worked any way. And 2. My water has NEVER been so clear and beautifully sparkling clear. I find (and so do countless others on this site and others) chlorine is cheaper and more effective than BAQ."

Jane S., California

I have a 15foot round X 42inch intex pool with a cartridge filter. I was using Baquicil and having nothing but expensive troubles. We emptied it, cleaned it, moved it, and refilled it. I switched to chlorine.

Susan Wood

Now that you've heard all the bad things, here are the advantages.


- Not affected by sunlight, temperature or pH

-May not irritate skin or eyes

-May not corrode pool equipment like oxidizers

-No smell

-Does not require a dispenser

-Degrades slowly

-Feels softer due to reduced water surface tension

Converting Biguanide Pools Back to Chlorine:

The following was emailed to us as a suggested method to convert back to chlorine:




A good time to switch may be in the spring, after a winter of not adding any baquacil or soft swim. I have heard reports of others who have said that they simply let their pool go very green, made sure the baquacil levels were 0 and then shocked it with chlorine. 


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