Biguanide To Sanitize Your Pool: Should You Use It?


by Rick Patterson

Did you know that chlorine isn’t the only chemical you can use to keep your pool water clean?

This may come as a shock since most pools rely on chlorine. Even saltwater pools, which are designed as a chlorine-alternative, use small amounts of it. But chlorine has its fair share of drawbacks.

Thankfully, there’s a game-changer when it comes to pool sanitization – and that’s biguanide.

What Is Biguanide?

Biguanide is a chlorine-free sanitizing liquid compound for your pool or hot tub.

Similar to hydrogen peroxide in its disinfecting and oxidizing capabilities, polyhexamethylene biguanide (PHMB) was originally created to be used as a surgical disinfectant.

Surprise surprise, it can also be used as an alternative to chlorine or bromine for cleaning pool water.

Chlorine sanitizes pool water via hypochlorous acid and hypochlorite ion, which kill microorganisms and bacteria in the pool water.

Biguanide works differently on contaminants. It doesn’t kill them, but instead, causes them to bind together. This turns them into insoluble clumps, making it easy for the pool filter to catch them.

There are a range of biguanide products on the market, and like “hoover” for vacuum cleaners or “kleenex” for tissues, biguanide is also often referred to by brand names such as:

  • Baquacil
  • SoftSwim
  • Revacil
  • Aqua Silk

Reasons To Use Biguanide In Your Pool

Bignuaide can make a big difference in the quality of your pool’s water, and there are a number of reasons for that.

It Produces Zero Chloramines

You know that heavily chlorinated pool smell that is present at some public indoor pools? That’s the smell of chloramines, which are a gaseous by-product of pools that have insufficient amounts of chlorine in the water.

When pools get really dirty, and the chlorine level becomes low, chloramines are formed. 

Chloramines are very dangerous to humans. They can irritate the eyes, nasal passage, throat, lungs, and skin. In some cases, people that are exposed to them for long periods of time can develop irreversible allergies to them and respiratory distress.

Well, here comes biguanide to save the day.

As biguanide doesn’t contain any chlorine (which is what chloramines are formed from), biguanide won’t produce them, or any other harmful by-products for that matter. 

This means you can swim in clean water and not ever have to worry about inhaling toxic fumes that could result in life-long damage to your body.

It’s Less Harsh On The Body

While chloramines are flat-out dangerous, some people are very sensitive to chlorine itself.

These sensitivities show up in various ways. 

For one, some people can get irritant dermatitis, which is essentially a mild chemical burn. It shows up as a rash or hives on the body. Skin can also become inflamed, tender, and itchy. 

People with asthma and other respiratory conditions like EIB and allergic rhinitis can also experience troubles due to chlorine. Things like sneezing, wheezing, coughing, chest tightness, and nasal congestion can all result.

Chlorine also bleaches and breaks down a pool’s vinyl liner as well as bathing suit fabrics over an extended period.

Biguanide won’t cause any of these problems. It’s decidedly less harsh, making it the healthier option to swim in as it’s more gentle on your hair, skin, eyes, clothing and doesn’t even smell!

It’s A More Stable Sanitizer

Another drawback of chlorine is that the pool requires you to frequently replenish it.

Due to its make-up, chlorine gets destroyed by the sun’s UV rays. During the summer months, chlorine consumption is even more pronounced. This leads to an increase in chlorine demand, which means you’re spending more money more often on it.

Even changes in the water’s temperature can cause you to use more chlorine, as you’ll have to re-balance the pH level when this happens.

Additionally, if there’s metals such as copper in the pool water, chlorine can oxide them. This can be a nightmare for those with blonde hair, as it will turn green. Unless you’re striving to look like The Joker, you’ll might want to seriously consider switching over from chlorine.

The inclusion of biguanide in your pool water will eliminate these issues. 

Sun/UV light won’t cause it to break down, it’s more stable in elevated temperatures (even in a spa), and biguanide won’t react with/oxidize any metals that may be present in the water.

Reasons Not To Use Biguanide In Your Pool

So we’ve established that biguanide has plenty of upsides, but are there any drawbacks to using it?

Limited Sanitization

Unfortunately, biguanide isn’t as effective as chlorine when it comes to full spectrum sanitizing.

It will still get rid of bacteria and algae, but it can’t remove other contaminants such as sweat/body oil, sunscreen, and other “body-related” pollutants.

In addition, over time, biguanide’s sanitizing effect may dwindle. This is because some microorganisms can build up a resistance to it. However, you won’t see them in the water, and you’ll really have no way of knowing if this is even occurring.

The good news is that by adding an oxidizing agent, which most biguanide pool care systems offer, you can get rid of all the contaminants in the pool. The downside to this oxidizer is that it’s another expense to add to your pool bill.

Can Result In Cloudy Pool Water

Unless you are 100% on top of your pool cleaning, using biguanide will probably cloud your pool water at some point.

Cloudy pool water happens because of how biguanide causes bacteria to cluster together. This is great because it makes the bacteria easy for the filter to catch.

But the downside of this is that a clogged up filter isn’t effectively cleaning all the water. Hence, cloudy water.

However, you can remedy this situation by adding some pool flocculant into the mix. Flocculant will cause hazy bacteria to bind almost immediately and fall to the bottom of the pool where you can vacuum it up.  

Pricier Than Chlorine

One of the biggest drawbacks to biguanide is the price tag that comes with it. 

Not only does biguanide cost more than chlorine does, but you have to use multiple products together. 

Most brands require you to use at least 3 different biguanide-related products in unison (they refer to it as a complete pool care system). 

Sure, biguanide will control bacteria, but then you need to include an algaecide, as well as an oxidizer for organic pollutants, and even a clarifier to keep the pool water sparkling.

Biguanide systems work well, but keep in mind you have to use them at least once a week, and their additional cost will add up quickly.

Biguanide Pool Chemistry (vs Chlorine)

Just as there is a certain chemical make-up that needs to be maintained in a chlorine pool, the same rule applies in a biguanide pool. However, there are some differences between the two.

Sanitizer (Duh!)

Biguanide sanitizer is the main component you’ll need to keep your pool water clean.

Where chlorine takes care of a myriad of contaminants (bacteria, algae, organic matter), biguanide sanitizer only tackles bacteria. 

Sufficient levels are between 40 and 50 parts per million (ppm), and it should never drop below 30 ppm.

Oxidizer Not Included

In chlorine pools, organic contaminants are easily destroyed. These take the form of body sweat and oils, sunscreen, urine and feces (hey, birds can poop in the pool, right?)

However, biguanide is only a sanitizer against bacteria. 

To get rid of these organic pollutants, you’ll need to add an oxidizing agent to the pool water. As a side benefit, the oxidizer will also help increase the sanitizer’s effectiveness against algae.

Take note that you can only use oxidizer that’s designed to work with biguanide sanitizer.

The Same pH Rules Apply

pH level refers to the water’s acidity, with the recommended range being 7.4 to 7.6 on the pH scale.

In chlorine pools, keeping this level balanced can be tricky as chlorine gets used up by contaminants and depleted by the sun.

A biguanide system is the same, so you should be retesting and balancing for pH level everytime you add sanitizer to the water.

Alkalinity Still Plays a Key Role

Total alkalinity works to keep drastic fluctuations in the water’s pH level from taking place. 

Fluctuations can happen any time the pool is subject to an outside influence such as the changing temperature, when swimmers or rainfall enter it, and when chemicals are added to the water.

Alkalinity needs to be above 100 ppm but lower than 150 ppm. If it drops under 100, the pH balance can massively spike or drop. If it rises over 150, the pH level will plunge causing scale and cloudy water.

Alkalinity can be controlled a few ways.

To increase it, use an pH increaser, or sodium bicarbonate.

To reduce it, you can use pH reducer, muriatic acid, or just wait it out as the total alkalinity will naturally drop over time.

Calcium Hardness Is Still a Thing

Similar to chlorinated pools, you need to have a bit of calcium in biguanide pool water. 

Too much and you’ll end up with a cloudy pool. Too little and the water can corrode concrete as well as any metals in the pool (things like ladders, etc.).

Increasing calcium hardness is simple to do by adding a calcium increaser until the desired level (between 175 and 275 ppm) is reached.

Decreasing calcium can be achieved a few different ways.

  1. Use a flocculant. This will clump up the calcium which can then be vacuumed out.
  2. Drain some of the pool’s water and replace it with softer water.
  3. Add muriatic acid to the pool, which ups the water’s saturation level and balances it out.

It Needs a Hand with Algae

It’s always recommended to keep your pool water chemistry properly balanced to stop pool algae from even forming in the first place.

But when algae is present in chlorine pools, the quickest and easiest way to remove it is with algaecide.

However, as this isn’t a chlorine system, you must make sure that the algaecide you use is designed to work with a biguanide sanitizer.

Pick Your Poison

Biguanide is a worthy alternative to chlorine pools, and some who have switched over swear they’ll never go back.

Whether you use a chlorine system or a biguanide system, keeping your pool water clean at all times is imperative to a safe and healthy pool. 

Categories: Pool Care, Pool Chemistry