Biguanide (PHMB) is the generic name of one of the more popular non-chlorine, non-bromine chemical sanitizers.  The main advantage is that no chlorine or bromine is required and there is little chemical odor.  Biguanide is an effective bactericide and can replace chlorine or bromine in that function.  However, chlorine or bromine are also oxidizing agents that can destroy organic contamination:  biguanide cannot destroy organic contamination and, therefore, concentrated hydrogen peroxide must be added to the spa or hot tub on a regular basis.   A disadvantage of biguanide is the development of biguanide-resistant micro-organisms, after several years of product usage.  This usually takes the form of a pink slime or water mold and the only recommended treatment is the application of large amounts of chlorine and/or non-chlorine shock.  This treatment destroys all of the biguanide present in the water.  Restoration of the biguanide regimen can risk a return of the problem and, therefore, a permanent switch to chlorine or an alternative form of sanitation should be considered.  Clicking on the underlined and highlighted "keywords" or "catch phrases," in the archived answers will give you access to additional information on that topic or product.  Please refer to the Glossary, if there are terms or phrases that require explanation.

My wife seems to be sensitive to chlorine.  I've tried bromine and that seems to be no better.  Could biguanide make enough of a difference?  Please advise.

H. S., 1/23/2004

Biguanide is an alternative to chlorine and bromine.  It is based on a totally different chemistry.  Actually, with biguanide you will not be able to use any chlorine or bromine -  even for shocking purposes.  A spa on biguanide can only use concentrated hydrogen peroxide for shocking purposes.  In your situation, biguanide is worth considering.  I suggest that the spa be emptied completely and cleaned before starting on biguanide or another alternative spa sanitizer.  There are some other alternatives to chlorine and bromine to consider: products such as ionizers, mineral sanitizers, ultraviolet (UV) sanitizers or ozone generators or a combination.  Look through the archives, on these topics, for more information.  Good luck.

Sincerely.  Alan Schuster, 1/23/2004

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I have been told that my spa has a water mold in it.  I have been using biguanide with good results, until recently.  How should I handle the problem?

Sam A., Columbia, MD, 9/14/2004               

Water mold is caused by a microorganism that has, unfortunately, become resistant to the biguanide.  In order to treat the problem, I suggest that you drain the spa and refill with fresh water.  Add some quick-dissolving chlorine or non-chlorine shock and make sure that at least a 1-3 PPM level of Free Chlorine persists overnight.  Add more shock, as necessary.   This will destroy the water mold on the surfaces and in the lines.  Resuming maintenance on biguanide will require that you once again drain the spa, refill and start from scratch.  Once a biguanide-resistant microorganism has developed there is no guarantee that it will not return, even after successful treatment.   For this reason, I suggest that an alternative sanitizer be considered:   chlorine, bromine, ozone generators, mineral sanitizers, ionizers, ultraviolet sanitizers or a combination.  Otherwise, you just might get the problem back, in spite of your best efforts. I hope that I have been helpful.   Good luck.

Sincerely.   Alan Schuster, 9/14/2004  

► Test Difficulties In A Biguanide Spa?  

I use biguanide for the spa and their test strips.  For some reason I find the results hard to read.  Especially pH always appears high, but when I have had the water tested at the spa dealer it appears to be in the correct range.  Is there another test strip or kit I can use for the biguanide system that will test pH, TA, Hardness, Sanitizer?  I have had problem with calcium & high pH that resulted the circulation pump going bad.  Thanks for your assistance

Dave, 1/27/2008

The test strips are convenient, but some people may have trouble reading the colors   For a better testing option consider using the ColorQ Biguanide PRO 5 Water Analyzer.  It is hand-held, all-digital and requires no color matching or look-up charts. It is quite reasonably priced and easy-to-use.  In addition to testing for biguanide, it tests the pH. total alkalinity, calcium hardness and Biguanide Shock levels.  It's the perfect tester, for those with any color vision impairment!   I hope that this information will prove helpful.

Sincerely.  Alan Schuster, 1/27/2008

► Spa Sanitizer Sensitivity?

I am having a problem with my hot tub. I have just switched over to biguanide as my sanitizer, as my wife has developed a reaction to chlorine  and bromine.  I cleaned and  fill my tub 5 days ago and have a high pH reading. I have been adding a granular pH reducer ever few hours for 3 days and can not get the pH down. I am also getting a reddish brown scum around the tub.  This scum is very sticky to touch and hard to remove. Can you give me some help. My tub is located indoors. Is this a factor?  Thank You.

Don G., Ontario, Canada, 8/12/2005

There have been some reports of problems with some brands of test strips.  I suggest that you have the pH verified by a local spa dealer.  There is no reason that the pH should be able to be lowered.  The LaMotte Insta-Test Strips do not seem to have any problems testing the pH in a biguanide sanitized spa.  The reddish deposits could be iron.  Have the source water tested.  If may be necessary to treat the water.  The problem may disappear if the pH is lowered.  The reddish deposits are very likely to be a bacterial slime, due to inadequate sanitation.  Check the sanitizer level.  Adding shock may be necessary.  Biguanide is a reasonable chlorine/bromine alternative for sensitive people.  However, long term use may cause sanitizer-resistant microorganisms to develop, requiring a switch.  You might consider using an ozonator and a mineral sanitizer.  It will be chlorine free sanitizing.  Another alternative is UV sanitizing, which is chemical free.  However, UV sanitizing must be used in conjunction with other products.  Good luck and I hope that this information proves helpful.

Sincerely.  Alan Schuster, 8/12/2005

► What Is Biguanide?

What is biguanide sanitizing that you mentioned?  You suggested against it but I've never heard of it.   I've been using chlorine, but considered switching to bromine.  It sounds like you prefer bromine.  I've been adding a lot of chlorine, much more than the dealer said I should have to add.  I test the water every couple days and need to add chlorine.  A friend has a very old hot tub and adds chlorine once a week.

Wondering, 3/30/2005

Biguanide is an alternative sanitizer, based on a chemical other than chlorine or bromine.  It is based on the polymer PHMB (polyhexamethylene biguanide) and can be useful for people with chlorine or bromine sensitivities, but is, otherwise, not something that I would suggest:  cost factor, tendency to foam and possible development of resistant microorganisms.  I do prefer bromine over chlorine:  less odor and less irritation potential.  How much chlorine a spa will require is more directly related to how the unit is being used, than by its size or age.  If you are looking to improve your spa sanitation and simplify maintenance, I suggest that you consider adding an ozone generator.  With an ozonator all you should need is 0.5-1.0 PPM of chlorine and it will take much less chemical to do that.  The ozonator will do most of the work and the chlorine will act as a backup.  Adding a mineral sanitizer will also reduce the amount of chlorine required and provide backup protection.  It works well with ozone.  I hope that this information proves helpful.

Sincerely.  Alan Schuster, 3/30/2005

► Milky White Spa Water?

OK - I haven't seen this one before.  I just bought a new house with a 300 gallon spa.  The owner drained and refilled the tub just before we moved in.  The water tested OK and looked beautiful.  My wife and I climbed in, turned on the jets and everything was just fine.  Then I turned on the blowers and everything turned milky white.  I have shocked and waited, but no improvement.  After this the water still looks great when only the filter or jets are running, but as soon as you hit the blowers, it happens again.  Any help is appreciated.  Oh yeah - biguanide chemicals in the water.

Steve C., Jacksonville, FL, 4/12/2004

Two possibilities.  The blower lines are coated with a biofilm (mold, bacteria, etc) and some of it is loosened when the blower is turned on.  The other possibility involves the biguanide itself:  this material has a tendency to foam and the blowers may be creating zillions of micro-bubbles that cloud the water.  To deal with the biofilm, you will need to shock with hydrogen peroxide and let the blowers operate to clean the lines.  So far as the foaming due to the biguanide is concerned, you may be able to control it by the addition of an antifoam.  If none of this works, it is possible that you have a water mold problem that has become resistant to the sanitizer.  Such problems are not uncommon with biguanide.  If that is the case, you will have to switch from biguanide to another sanitizing method.  My suggestion would be to use an ozonator and a mineral sanitizer or bromine.  I have no doubt, that you will be happy with either method.  I hope that this will clear things up.

Sincerely.  Alan Schuster, 4/13/2004

► What To Do?

Dear Alan, I could not find this question addressed anywhere, so here goes.  We bought a spa 6 mo. ago and it arrived with a Biguanide Spa start-up kit.  Our spa has an ozonator and we have used the chemicals with relative success.  However, they are pricey.  We heard from a spa salesperson that simply dropping a bromine tablet into the filter area once a week.  That sounds too simplistic to me.  I know that there are pH levels that need checked and maintained and also shock treatments that he never mentioned.  What do you recommend I use?

Mary S., Fremont CA, 1/21/2004

I would like to stop using biguanide and switch to an Ozonator and an Ionizer.  I want to use as few chemicals as possible.  Is there anything that I should do before switching over?  Thank you.

The Kelly Family, NJ, 3/22/2003

Spa water has to be replaced on a regular basis, so you might as well start there.  That way you start with a clean page and avoid the chemical buildups, that may have previously occurred.  Thereafter, the spa water should be changed on a regular basis depending upon your usage patterns or at the first signs of a loss of optimum water quality.  In any event, not more than 3 months is recommended without a water change.  Enjoy the spa.

Sincerely.  Alan Schuster, 3/23/2003

Gary J., Chatsworth, GA, 1/3/2004

The water mold and the resultant cloudiness are the result of the formation of a biguanide-resistant microorganisms.  The cleaning and treating with chlorine are only temporary:  it is resistant to biguanide and will, in all likelihood, return quickly.   I suggest that you permanently switch from biguanide to another sanitizer.  To reduce the chemical effects of bromine you should add an ozonator, as this will allow you to maintain proper conditions with much lower bromine levels.  To completely eliminate bromine, you could use an ozonator and with a mineral sanitizer or ionizer.  In any event, it is time to move past biguanide.  I hope that I have been helpful.

S.E.B, 11/17/2003

The active chemical is a polymer called biguanide:  abbreviated PHMB.  This material is incompatible with chlorine or bromine and is a popular alternative to these sanitizers.  While it does function as a spa water sanitizer, it cannot perform the necessary oxidizing action that is needed to destroy organic wastes and accumulations.  For this purpose liquid hydrogen peroxide is used.  For someone sensitive to bromine this is a reasonable alternative.  Another viable alternative spa water sanitizing method would be the use of an ozonator with either and ionization unit or a mineral sanitizer.  In this case the ozonator provides the necessary oxidizing action and the ionization or mineral sanitizer provides a source of metallic ions - silver and zinc or copper - that act as water sanitizers.  Less chlorine or bromine will be needed, on a regular basis.  I hope that this information proves helpful.

My spa was supplied with an Ozonator already installed.   I currently use some bromine to act as a back up.  Would it be possible to stop the bromine and start using biguanide as a back up?  I think that my wife is sensitive to bromine and chlorine.  Thank you.

Marc P., 2/3/2003

Yes, you can use biguanide and ozone based on a leading biguanide manufacturer's recommendations.  I suggest that you start by draining and cleaning the spa.  That way you'll get rid of all of the bromide salts and start off with a clean slate.  You should only need to maintain a minimum level of biguanide, because of the Ozonator.  Follow the directions on the label and test a least twice weekly, until you get a handle on how much biguanide you need to add periodically.  Biguanide has a tendency to foam and that could interfere with the venturi (vacuum siphon tube) effect, by which ozone is added to the water.  There is another possibility that you might want to consider.  Why not use an Ionizer or a Mineral Sanitizer with your ozonator?  If sensitivity to chemicals is a consideration, this makes a lot of practical sense.  Browse through the archives for more on the topic.  Good luck and I hope that I have been helpful. 

Sincerely.  Alan Schuster, 2/3/2003

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