An Alternative Pool Sanitizer

Biguanide (PHMB) is the generic name of one of the more popular non-chlorine, non-bromine chemical sanitizers used in swimming pools.  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 swimming pool on a regular basis. A disadvantage of biguanide is the development of biguanide-resistant micro-organisms, after a few 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.

ColorQ Biguanide PRO 5 Water Analyzer

► Doing It Wrong?

I have a 24' above ground with an old DE filter that was clear about a month ago, but has been cloudy for the most part since.  I used biguanide as the previous owner had but, after a week away, shocked the disgusting pool with chlorine-based shock treatment.  It's been a couple of weeks since, and it's still cloudy although the readings for pH, biguanide and alkalinity seem to be in line.   I wonder how well the filter is working.  I put a cup of DE at the beginning of the day and backwash at the end.  There is green in the backwash, but the pool is still cloudy overall.  I need serious help.

Ilana G., 8/20/21

You have to make a decision!  You can use chlorine or you can use biguanide - you can't use both.  The effect of adding the chlorine was to destroy some of the biguanide.  This by itself can cause the water to turn green.  If you want to use biguanide, you must use hydrogen peroxide to shock the pool.  If you want to use chlorine, you must add enough to completely destroy all of the biguanide and enough to deal with any algae.  Conversion to chlorine will require about 4 gallons of liquid chlorine for each 5,000 gallons of water.  The water will discolor.  Check to make sure that there is free chlorine present and add additional shock, as might be required.  Once the free chlorine level is established. the pool can be maintained in a typical manner.  You seem to be operating the DE filter, as if it were a sand filter.  It is not customary to add small amounts of DE to the skimmer.  Either the DE has to be completely replaced, after the backwashing or the filter can be "bumped" and no additional DE is required.  Consult a local dealer about your particular filter's requirements.  Browse through the archives on biguanide and filtration problems for additional information.  To better assure proper overall pool water chemistry, visit a pool store that has a very reliable, professional lab such as a WaterLink or Pinpoint system, rather than a less accurate test kit or strip reader.  To locate a dealer near you, go to:  www.lamotte.com/pages/pool/expdeal/index.html  I hope that I have been helpful.

Sincerely.  Alan Schuster, 8/21/2003

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► Perplexed?

I have been using biguanide for several years and been happy with the results.  It may cost more, but I like the feel and the lack of chlorine odors.  The problem is that on two occasions the pool has developed a water mold.   I had to add chemicals and chlorine shock and, in effect, had to start all over.  The dealer says it could happen again.  Short of switching to something else, can you suggest something?  Thanks.

Paul B., Lake Worth, FL, 9/4/2003

You could try adding an Ultra-Violet Sanitizing unit.  It will depress the microbial populations and help prevent a possible recurrence.  If the problem does recur, you really should permanently switch from biguanide.  In that case, you could change to chlorine or bromine and the UV unit will allow you to maintain satisfactory sanitizer levels with fewer chemicals.  It's your call.  Good luck with your decision.

Sincerely.  Alan Schuster, 9/5/2003

► Pool Water Mold?

I have been using biguanide for the last 4-5 years with good results, at least until this year.  I had a battle with water mold - whatever that is - and after spending a small fortune getting rid of it, it seems to be coming back again.  What would you suggest?  Thank you. Frustrated in Freehold.

Kelly E., Freehold NJ, 7/3/2003    

Water mold is caused by a microorganism that has unfortunately become resistant to the biguanide.  In order to treat the problem, various chemicals such as chlorine shock or non-chlorine shock, have to be added to the water until a Free Chlorine level of 5-10 PPM is achieved.  The water will go through various green-brown-cloudy stages, until finally the water clears up.   It takes a lot of shock, at least 2 pounds per 5000 gallons, in order to complete the treatment.  A consequence, of adding the shock, is the destruction of all of the biguanide.  Resuming maintenance on biguanide will require that you start from scratch and this is why it has become so expensive.  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, ultraviolet sanitizers, ozone generators, mineral sanitizers, salt chlorine generators, ionization-oxidation units, ionization 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, 7/3/2003

► Biguanide Testing?

I have used a biguanide test kit with the dropper bottles and test strips.  I can't say that I like or feel confident about having to match the colors.  Is there any other way to do the testing?  Thanks for the help.

Brad M., Naples, FL, 1/26/20078

Good News!  The ColorQ Biguanide PRO 5 Water Analyzer is an all-digital, hand-held tester that performs tests for biguanide, pH, total alkalinity, calcium hardness and biguanide shock.  There are no colors to match and no look-up charts.  It is an ideal tester for anyone with color matching difficulties.  And it is affordably priced and easy to use.  Seems to  be just what you are looking for.  I hope that this information will prove helpful.

Sincerely.  Alan Schuster, 1/27/2008

► Not A Happy Camper?

I am tempted to put a sledge hammer to the side of the pool and just start using a "cool" bathtub!  Hope you can help:  first off Alan, I use and have used biguanide in my pool for the past 5 years or so and have never encountered a problem.  This year however was nothing short of a nightmare.  When I pulled the cover off in May, I had brown, green cloudy water, a few bags of non chlorine shock and a week of filtering took care of the green brown issue and slightly helped the cloudiness.  I then balanced my pool with 15 lbs. of calcium hardness, alkalinity increaser etc.  I also got my biguanide levels up to par.  BUT, the pool was still cloudy/hazy.  I then changed the sand in the filter and filtered another week (24/7) and the pool is still hazy.  I went to my pool gal (who's very knowledgeable) and she sold me a " Filter Aid."  basically it's a dry powder added with water to make a "slurry" and poured into the skimmer.  I was told that within 8-12 hours the filter pressure will rise by 10 points, my pool will be crystal clear and at that time, I should backwash.  I filtered for a week straight and the pressure never rose more than a point.  I backwashed anyway and the backwashed water cleared within a few seconds.  But, still the water was cloudy.  I decided to take the cap off the filter and found this "slurried" solution I poured in a week earlier had hardened into a 3 inch thick shell.  So I cleaned out the filter and changed the sand AGAIN.  I ran it another day or two and still no clearing up.  I poured into the skimmer, a flocculant (dry granules) and the water got worse.  I tried it again with the flocculant the next day and now I can't see the bottom of the pool.  What can you tell me Alan?  I'm ready for the nut house.  Again, I NEVER had problems like this before.  Thanx much.

Steve M., Kunkletown. PA, 7/6/2006

You told me a lot but there are gaps.  You cannot use non-chlorine granular shock with biguanide, as it will decompose the biguanide and will not solve the problem.  Only hydrogen peroxide can be used as a shock treatment.  The filter aid should not have caused that to happen.  It is either contains some other additives or there is something that coagulated it in your pool.  Biguanide can do that!  But, why would they recommend the product, if you are using biguanide?  Freshly filled sand filter can be very inefficient and the dead algae and debris might be passing right thru.  Ordinarily, I would suggest adding some DE to the skimmer.  But DE will be coagulated by the biguanide.  Make sure that the biguanide level is OK.  Add some more hydrogen peroxide.  LaMotte makes a test strip that can test for peroxide - maybe the dealer has the item.  There is a possibility that the floc - if it was aluminum sulfate - got into the pool.  This being the case, it could contribute to the cloudiness, until it is completely removed.  Raise the pH to 8.0 and shut off the filter.  The next morning vacuum the bottom to waste.  This should remove all of the flock and may even give you clear water.  Now for the bad part.  It is not unheard of for long time biguanide users to develop problems with white water mold.  This may be part of your problem.  However, it is difficult to say this with complete certainty.  The treatment for this problem is the complete destruction of all the biguanide and the establishment of a 1-3 PPM level of Free Chlorine.  At this point your pool is on chlorine and it should destroy the water mold.  Switching back may bring a return of this problem.  It takes about 4 pounds of non-chlorine shock or 4 gallons of liquid chlorine per 5,000 gallons, to destroy the biguanide.  Depending on the condition of the water, even more could be required.  Thereafter, boost the Free Chlorine to about 5-10 PPM.  The decomposing biguanide will consume the chlorine and the pool will go thru a green-brown stage.  There are lots of alternatives that minimize the use of chlorine and you might look into them:  UV Sanitizers, Mineral Sanitizers, Ozonators, Salt Chlorine Generators and Ionization-Oxidation units.  Some can be used together, for even better results.  I hope that this information proves helpful.

Sincerely.  Alan Schuster, 7/7/2006

Thanx much Alan.  I just returned from my pool gal and she states that the problem is water mold.  My shock level was low even though I poured it 4 days ago.  I'll ask you though Alan, IS THIS the time to forget about biguanide and just go with chlorine from this point forward?  After reading your email, I see that this may not be my last battle with water mold.  Also, the filter aids and flocculants I used were both biguanide related products, assumingly safe for biguanide pools.  I will shut everything down and see what the water looks like tomorrow.  Alan, thanks so much for your advise.

Steve, 7/7/2003

Tomorrow may bring clear water.  BUT, the mold will still be there, lurking and ready to start trouble all over again.  This is a biguanide-resistant organism and once it appears, I think that a switch to another sanitizer is the best thing to do.  There are lots of alternatives to ordinary chlorine to choose from:  UV Sanitizers, Mineral Sanitizers, Ozonators, Salt Chlorine Generators and Ionization-Oxidation units.  Many can be used together, for even better results.  I hope that is clears up for you.  Have a good summer.

Sincerely.  Alan Schuster, 7/7/2003

► Bad Conversion Advice?

► Wild Shade Of Pool Water Colors?

I was advised by my pool dealer to let my biguanide level drop, slowly begin treating the pool with chlorine via tablets in the skimmers, and finally use a chlorine shock to "eat up" the biguanide.  I did as told and all went well until I added the shock.  My water turned a wild shade of green/yellow/brown.  A day later it is now a murky sea foam green color.  I think I should have used a non chlorine shock from what I have now researched via the internet.  My question is what do I do now that I'm in this mess?  Help Please?  Thanks.

Ron, 6/3/2006

The preferred method to destroy all of the biguanide, according to a leading biguanide manufacturer, is to add 4 pounds of non-chlorine shock per 5,000 gallons of water.  Chlorine will accomplish much the same end result.  It is normal for the water to undergo a color range, as you have described.  All of the biguanide will not be eliminated from the water until you are able to maintain a stable Free Chlorine level and the water clears up.  At this point, I would add 2 pounds of non-chlorine shock for each 5,000 gallons of water.  How much shock will be required will depend upon the biguanide concentration and the condition of the pool water.  Algae filled pools will require much more shock!  I believe that if you are going to make a switch to chlorine, the sooner and faster you add the shock - the better.  There's no point in prolonging a period of discolored water and inadequate sanitation.  The color will return to normal, as soon as all of the biguanide has been decomposed by the shock treatment.  Afterwards, resume normal chlorination.  I hope that I have been helpful.

Sincerely.  Alan Schuster, 6/3/2006

► Biguanide Filtration Issues?

Can I use Zeobrite in my biguanide pool?

A.G., 5/3/2007

Sincerely.  Alan Schuster, 5/4/2007

► All Gummed Up?

► Damage To Plastic Components?

► Chlorine To Biguanide?

Currently my pool is being maintained on chlorine.  I'm thinking of switching to biguanide.  I heard that there is no chlorine smell.  Is there anything I have to do before switching over?  Thank you.

Phil H., Mt. Ephraim, NJ, 7/22/2004

In order to start using biguanide, it is necessary to eliminate all of the chlorine in your pool.  For that purpose, the biguanide manufacturer provides a chlorine neutralizer product.  Copper and silver algaecides might, also, present a problem.  If you have ever used either product, I suggest that you bring in a water sample for analysis.  The dealer should be able to determine, if any additional steps, are required.   Good luck with your decision.

Sincerely.  Alan Schuster, 7/22/2004

► Is Draining To Convert Necessary?

Can I use a cartridge filter pump with a 16’ X 24’ above ground pool utilizing a biguanide system?  We want to convert from a chlorine system and  we are draining the pool, but I want to make sure that we have the right type of pump for this system.  Thanks! 

Eileen, 5/26/2005

You don't have to drain the pool.  Draining could result in the liner shrinking or structural damage. Conversion is simple.  Add 4 gallons of liquid chlorine for every 10,000 gallons of water.  The chlorine will react with the biguanide and start to decompose it.  As this happens the pool will go through cloudy and discolored states.  This is normal.  Periodically test the FREE CHLORINE level!!!  You have to repeat this dosage.  Only after enough chlorine has been added to register a stable FREE CHLORINE level, will enough have been added so as to destroy the biguanide, algae and debris.  From this point on you should be able to maintain the chlorine level with normal product additions.  During this time, adjust the pH, total alkalinity and add chlorine stabilizer.  If you are interested in maintaining the pool with chlorine and at the same time getting better water quality with less effort, you might look into a salt chlorine generator.  It will give you everything that biguanide could not.  No more chlorine to buy, handle or store!  Enjoy the season and I hope that this information proves helpful.

Sincerely.  Alan Schuster, 5/26/2005

► Looking To Switch?

I noticed you keep referring to "automatic pool cleaners."  We have one that is water powered.  It has a net attached to a hose and water jets propel debris into the net. Is this the same thing?  Is this good enough to keep circulation going on the bottom of our above ground pool?  We have been having an algae problem lately and I was wondering if we should use the cleaner more often?  Also, we have been using biguanide products in our pool.  Is it safe to use chlorine instead?  The biguanide just doesn't seem to be doing the trick, but I don't want anything we put in the pool to harm the liner.  Thanks for your help.

Cindy R., 6/16/2005

The automatic pool cleaner that you have is fine.  It will remove the coarser debris and stir up the silt for removal by filtration.  It will help improve the circulation across the bottom and that can aid in algae control.  In order to switch from biguanide to chlorine, you will have to add enough non-chlorine shock or liquid chlorine to completely destroy all of the biguanide and establish a level of Free Chlorine.  Start with 4 pounds or gallons per 5,000 gallons of pool water.  The pool will go through a cloudy green to brown stage, but it will clear up, once a Free Chlorine level has been established.  Thereafter, maintain normal chlorination.  I hope that I have been helpful.  Enjoy the summer.

Sincerely.  Alan Schuster, 6/16/2005

► Off To A Springtime Disaster?

Alan, your site is just what us pool owners need, especially us confused ones.  My pool description is as follows: in ground, approx. 10,000 gal., fiberglass, 1 HP pump, 90 sq. ft. cartridge type filter.  Late last summer I switched from a non-chlorine sanitizer to chlorine. The switch went fine, water was clear. However, when I shocked periodically I noticed the water took on a slight green tint but stayed perfectly clear. This would go away after a few days. This was the water condition when I covered the pool for the winter. A little over two weeks ago I uncovered the pool and almost got sick. There was a brown, green, black ring around the water line and the water was dark green and very cloudy. The return nozzles and the top step were not visible. Since that time, upon advice from the local "expert", I have added around 15 lbs. of shock and added algaecide on numerous occasions. At least now I can see the bottom enough to vacuum; there was very little debris on the bottom. All chemical readings are within limits or very close with the exception of cyanuric acid which is high; from the excessive shocking I guess. When I do shock the water becomes greener and cloudier and stays that way for several days. Also, there is now a brown ring at the waterline and below. The filter cartridge has been cleaned repeatedly using muriatic acid, possibly it's not doing as good a job as it should. The back pressure on the filter is 12-13psi when the cartridge is clean and I let it rise to around 20-22psi before I clean it. At around 20psi the flow is greatly reduced. The cartridge is green when I remove it for cleaning but the "greenness" of the water doesn't seem to be decreasing much.  Progress seems to have stalled; what should be my next step? Would putting chlorine tablets in the skimmer help? Should I keep shocking to the point where the chlorine level is maintained around 10? I have read that sodium bromide can be used to reduce the cyanuric acid content; is this true and is it worth doing? Is the brown ring caused by excessive algaecide and what is the best thing to use to remove it? We swam in the clear water with the slight green tint last summer but I sure wouldn't swim in what I have now; is there some definitive deciding visual factor that says swim or don't swim?  Thanks in advance for your help.

Was this non-chlorine sanitizer biguanide?  If so, it explains everything.  Switching from biguanide to chlorine requires that enough chlorine be added to completely destroy all of the biguanide.  In the course of destroying the biguanide, the water can discolor green-brown.  Last fall you did not destroy all of the biguanide and closed the pool without any chlorine and inadequate biguanide levels.  You have to boost the Free Chlorine up to a stable level of 1-3 PPM.  Keep adding shock, every few hours, as necessary.  Once all of the biguanide is destroyed the water will clear up.  If there is algae present keep the Free Chlorine level raised until that is eliminated.  Once the problems are solved, resume normal operations.  Sodium bromide will not remove cyanuric acid!  Whatever you read is mistaken.  A cyanuric acid level over 150 PPM is too high and will require a partial replacement of the pool water.  Levels below 150 PPM may be above the ideal, but are manageable.  This information assumes that you were using biguanide.  If not the case, write me back.  The time to swim is when the water is clear and there is a stable free chlorine level.  Soon, just do what needs to be done!

Sincerely.  Alan Schuster, 5/11/2004

► Shocking A Biguanide Pool?

I know that chlorine shock can't be used in a biguanide pool, but what about a non-chlorine shock?  I would like to avoid the hydrogen peroxide.  Thanks for the help.

Allan G., Staten Island, NY, 6/2/2003

Non-chlorine shock is potassium peroxymonosulfate.  It is also called potassium monopersulfate or monopersulfate compound.  No matter what you call it, you can't use it with biguanide.   Hydrogen peroxide is the product of choice.  Special Test Strips can be used to determine, if enough peroxide has been added.   Adding non-chlorine will destroy the biguanide and that will accomplish nothing.  Enough said?  Enjoy the season.

Sincerely.  Alan Schuster, 6/2/2003

► Biguanide To Chlorine?

I have been using biguanide for the past several years.  The results have been good, but I would like to reduce my pool expenses, for the upcoming pool season.  I will be opening the pool in about 6 weeks and I would to convert to a automatic chlorinator.  What do I need to do to keep it simple and inexpensive?  I have a cartridge filter.  Thanks.

Pete S., Wilmington, DE, 4/23/2004

Remove the cover and get the water level up and the filter operating.  Add  4 pounds of a quick-dissolving chlorine shock or a non-chlorine shock, for each 5000 gallons of water.  The water will discolor.   Test the Free Chlorine level.  It is important to establish a 1-3 PPM level of Free Chlorine.  Add more shock, as necessary, until this is accomplished.  Once this level has been established, the discoloration will disappear and all of the biguanide should have been destroyed.  Normal chlorination should be started, at this point.  Of course, the pH, TA and calcium hardness may have to be adjusted.  The chlorine conditioner level should be 20-30 PPM.   If there is some cloudiness, try one of those "Blue" Clarifiers.   Adding an algaecide would be a good idea.  It is a good practice to clean your filter thoroughly, in order to remove decomposition products that might be present.  Just about the easiest way to clean the filter cartridge is with The Blaster.  Basically, your only extra costs will be the shock and the stabilizer.  Good luck and enjoy the season to be.

Sincerely.  Alan Schuster, 4/23/2004