Pool Chemistry 101

Pool Chemistry can be a little intimidating at first, but with the help from this guide and our staff, most customers get the hang of it within their first season.  Please note that this guide should not be used for a solution to any problem, but rather a set of guidelines to help inform you.  Always visit your local pool or spa store when questions or concerns arise until you get the hang of everything, and even then a little reassurance never hurt anyone.

The Core of Any Swimming Pool or Spa Maintenance

The three parts of a proper chemical system involve Sanitization, Balancing the Pool, and Oxidizing. We'll dive into what these three parts are before we go any deeper.


A sanitizer is what keeps your pool safe. It kills microorganisms (germs), such as bacteria, viruses, and amoeba. It is what keeps your water safe for bathers, and must always be maintained at a proper level at all times. What's worse is some sanitizers do not work as efficiently when the pools balance is off. Even if a blow up pool, the water might be safe until the first bather enters and introduces contaminants. Additionally, chlorine needs to be shielded from the sun (think of it like Sunblock for your chlorine), so a Stabalizer (Cyanuric Acid) must be used. Most chlorine sticks and pucks are stabalized, however salt pools need to be stabalized to reach the minimum threshold for safe sanitization. Lastly, the simple rule is to never mix two different types of chlorine as they are extremely reactive and could build pressure in your pump resulting in a increadibly dangerous situation (we've heard of stories of the pump exploding and birds dropping dead out of trees). Our products are color coded and labled to avoid any confusion.

Balancing Chemicals

In order to make sure your sanitizer is working effectively and to avoid damage to your pool and equipment, the pool must be properly balanced. Balancing the pool involves keeping the pH, Alkalinity, and Calcium Hardness in proper ranges. These levels can vary depending on what chemical system you are using and what material the pool is made out of (vinyl, plaster, or fiberglass). We'll cover the three core balancing chemicals below.

Balancing Chemical: pH

A simple definition for pH is the measure of a acidity or basicity in your pools water. The pH scale is logarithmic, meaning that when the number changes it actually changes by 10 times. So a 7.2 pH reading is actually 10 times more acidic than a 7.3 pH reading. A 7.0 pH reading is considered neutral. The human eye is usually around a 7.2 to 7.4 pH reading. For swimming pools you generally will want to aim for a 7.2 to 7.5 pH reading. It is important to note that some systems, such as chlorine generators, aka Salt Pools, produce Sodium Hydroxide (lye) which is extremely basic. Therefore pH will have to be much more closely monitored. Chlorine (and Bromine to a lesser degree) work better at lower pH's (within the ranges mentioned above), and start to get less and less effective at higher pH's, but that is outside the scope of this tutorial. To lower pH we recommend a dry acid, as they are significantly safer. Muratic Acid may be used, but remember it is a diluted (but not weak) Hydrochloric Acid and if it splashes on your skin, it will chemical burn you. In addition, Hydrochloric Acid can form a mist that has a corrosive effect on human tissue. Again, the use of a dry acid is HIGHLY recommended and only marginally more expensive.

Balancing Chemical: Alkalinity

Heavily related to pH is Alkalinity. Alkalinity acts as a buffer for your pH, preventing it from bouncing around when there is a bather load, water is added, or chemicals are added. In fact, just about everything that is added to the pool could alter the pH and that's where Alkalinity comes into play. One of the hardest our customers have when they are first learning water chemistry is pH and Alkalinity, and that is because when you lower the pH you also lower the Alkalinity. But when you raise the Alkalinity you also raise the pH. You just don't do so with a one to one ratio. Our recommendation is to always start with the lowest one first. So if your pH is low and your alkalinity is normal or high, alter your pH first. Alternatively if your pH is high and your alkalinity is low, start with the alkalinity. It is recommended that alkalinity be maintained at a 80 to 120 ppm, but this number can vary depending on the system you are using. Some products, especially Copper based Sanitizers, require that Alkalinity be adjusted slowly, and this is because a sudden addition of Alkalinity could cause the copper to come out of solution and potentially stain your pool. Always follow the bottle recommenations, or stop by a pool store and get your water professionally tested to ensure you are doing everything as correct as possible.

Balancing Chemical: Calcium Hardness

Simply put, your pool needs to have a proper Calcium reading to prevent staining and scaling. When the calcium gets too low, the water will pull Calcium from either the surface of your swimming pool or the equipment itself, which can cause serious and expensive damage. When the Calcium gets too high, the can cause scaling (that white substance that builds up on the surface line, in plumbing, and on equipment, which can not only be a nightmare to clean up, but also expensive on your equipment). The recommended levels for calcium, again this depends on the system you are using, and the material of your pool, is 200 - 400 ppm (parts per million). In many cases, our staff is trained to aim for a 150 ppm, because it is ample and does not run the risk of adding too much calcium to the water. The reason this is important is there is no chemical to reduce your Calcium level, you must partially drain and refill. There are chelating agents which bond to with the calcium to prevent, trapping the Calcium in it's solution, but most of the time it's just not a viable option in terms of cost.

Oxidizing your Pool

Without going into too much detail (this one goes into Redox reactions, if you remember that from Chemistry Class), an Oxidizer can be thought of as a way eliminate (Oxidize) organic materials in your swimming pool or spa, such as Oils. In chlorine pools, this is also commonly called "Shocking" the pool, because by adding enough chlorine at the same time, you can reach a "breaking point". Chlorine pools are actually very unique, as there are two types of chlorine, Free Chlorine and Combined Chlorine. Combined Chlorine is the "bad" or "used" chlorine, which oddly enough leads to the chlorine odor in a swimming pool. By using an oxidizer in a chlorine pool, you can help turn that Combined Chlorine back into Free Chlorine, simply by adding enough chlorine to reach a 10 ppm FAC (Free Available Chlorine). Pools with chlorine generators (salt pools) often have a "Superchlorination" setting, which generally run the salt cell for 24 hours in an attempt to reach the mentioned threshold of 10 ppm FAC. Unfortantely this is not always the case, and additionally this is not a true "Shock" (remember you want to hit that 10 ppm quickly). We recommend using a Chlorine or Non-chlorine shock, even if you have a chlorine generator at least weekly, and it happens that this will extend the life of your cell. Remember to always cut the salt cell off when you add Calcium (or Salt for that matter) which many of the best shocks on the market contain. Just leave the cell off long enough for the chemical to fully dissolve. Lastly, all pools should be shocked at least once weekly, and after heavy bather loads and/or storms (rain and debris).

Chlorine Only: Stabilization

It was briefly mentioned in our Sanitization section, but stabalizing your chlorine (in an ourdoor pool) protects your chlorine from UV light. Much like our skin can burn in such light, so can chlorine, so a stabalizer (Cyanuric Acid) helps protect your chlorine from the sun. Bromine cannot be stabilized, and such is not recommended for outdoor pools. But watch out, too much stabilized is a bad thing. Most chlorine pucks (3" Tablets) and sticks are stabilized, and some oxidizers such as Sodium Dichlor is stabilized, so there is the potential for overstabilization. Only recently has a chemical solution been developed to remove Cyanuric Acid from the water, and it is not readily available on the market yet, so the only practical solution is to partially drain and refill, much like Calcium however with Stabilizer it's a little trickier. If you were to drain 50% of your pool's water, and refill, your stabilizer level might only go down by 15-25%. This is because it tends to be more concentrated at the deepest sections of your pool. With that in mind, drain from your main drain (if you have one), or take a Vacuum Hose, Vacuum Head, and Telescope Pole, and set it upside down in the deepest end of your pool, and let the pool drain from that.

Algae, then Algaecides

In theory, if everything is always sanitized, balanced, and oxidized, and the levels are maintained 100% of the time, your pool should be naturally resistant to Algae. Also, a side note, Algae itself is not dangerous to swimmers, however it may be an indicator that the pool is not (or has not been) properly maintained, and at that point it could be dangerous. Once you have Algae it will consume your Sanitizer and Oxidizers at a much faster rate, than if the pool where to have no visible Algae. Algae can also lay dorment in hidden areas of your pool (such as in the filter). Two food sources for Algae are Sunlight and Phosphates. Because of the nightmare that Algae can (and at some point in your pool chemistry experience probably will) cause, it is highly recommended that you use a Preventative Algaecide.


As mentioned above, the use of a Preventative Algaecide (or Algicide) is strongly advised in all Swimming Pools. Spas that remain covered pose virtually no (although it's not unhead of) risk for Algae. A preventative Algaecide will save money in the long term, because once Algae takes root, it can be costly. The other type of Algaecide is a Treatment Algaecide. The suffix -cide means to kill, so that is sufficient in explaining what this chemical product actually accomplishes. Both Preventative and Treatment Algaecides can kill Algae, however Treatment Algaecides are more heavily concentrated. Algae tends to stick to the surfaces (the walls) of your pool, and can act as a barrier for chemical treatment, so brushing the walls daily once Algae develops is a necessity to help get the Algae back into the water for your chemical products to eliminate it. Backwashing a Sand Filter, Backwashing and new Diatomaceous Earth (DE Powder) to a DE Filter, and Chemically Cleaning a Cartrdige Filter is strongly advised after your pool starts to clear up. Unfortunately most customers choose to ignore the advise on a Preventative Algaecide, which is why some of the treatment plans (including the manual labor) are mentioned here, but just remember by using a Preventative Algaecide, you are taking a step into avoiding a headache in the long run. Also, many customers, for some reason, think Algae cannot grow in Salt Water, but the fact is Salt Pools have just as many Algae problems as traditional chlorine sanitizaiton pools, so a Preventative Algaecide is still strongly recommended for them. We recommend Poolife Defend+ as a Preventative Weekly Algaecide, Poolife AlgaeBomb 60 as a Treatment Algaecide, and AlgaeShield by Earth Science Laboratories, Inc. as a Premium Monthly Algaecide (which can be used as a Preventative Monthly and Treatment Algeacide.)

Phosphates, and then Phosphate Removers

This particuar topic is a tricky one. We mentioned that Phosphates are a food source for Algae. When Phosphates Removers first hit the swimming pool market, many dealers, ourselves included, where misproperly trained, and overemphasized the concept. Today, we take a resonable approach. At the beginning of each season, we test for Phosphates, and expect to see some level of Phosphates. We're only concerned at extremely high levels -- even if the Swimming Pool is clear. From there, are concern with Phosphates only comes when an Algae problem develops, because at this point the food source ultimately needs to be dealt with after the Algae is treated so it cannot easily return. Some customers choose to use Phosphate Removals as part of their regular maintenance routine, and this is acceptable, as it will not hurt the pool, but this is optional if there is no Algae problem. Phosphates come from many different places, including water run off (especially from landscaping), and from County or City water, as many places now use phosphates to help clean and flush their lines (which can cause a headache for swimming pool owners). Occationally test your tap water for Phosphates to see if this might be a concern for you.

Chemical Phosphate Removers

At the start of every season, have your Swimming Pool Company test your water for Phosphates. These tests also exist in a test tube and pre-dosed strip form that you stick into the tube form. If your levels are high, treat them then. Otherwise, unless an Algae problem arises don't worry about it. You can always ask your Swimming Pool Company to run the test for you, even if there is no problem, just for reassurance. When treating for Phosphates, generally a liquid solution is used, which will sequester (cause it to stick together) and become trapped in the filter. The filter must be cleaned after application, as it will cause poor water circulation, and ultimately damage to the pump in the long run. For maintenance Phosphate removers, just keep an eye on the pressure of your filter, and when it goes up 10 PSI above where it normally is, clean your filter. A breif explanation for cleaning your filter are explained in the Algaecides section.


This one is rare, but does occur in Swimming Pools. It is namely caused by run off from fertilizer. Swimming Pool Companies seldomly check for it, but you can always ask for a Nitrate test if you feel this might be an issue. Test Strips can be used to test at home, and some customers choose to use Aquarium testing kits. Nitrates will eat up your sanitizer (namely Chlorine), and you won't be able to hold a chlorine level. It might cause the pool to look like it's in a "Chlorine Lock" (which will not be covered in this tutorial). An extremely large dose of chlorine is used to break up Nitrates, and because of this, we highly recommend that you goto your Swimming Pool Store to find out how to dose this (at the necessary level you could cause damage to your pool).

Minerals to Reduce Chlorine or Bromine Levels

In both Pools and Spas, Minerals (silver and copper) can be used to lessen the levels of Chlorine or Bromine sanitizer needed. Don't use these systems if a bather has a senstivity of allergy to heavy metals. While these systems work, in theory, they cause one problem. Because you are running the sanitizer level at a lower level, when the Sanitizer level drops (and it will), there isn't much threshold. For example, one product might recommend a 0.5 - 1 ppm FAC in a spa, where traditional chlorine levels for 3 - 4 ppm in a Spa. That means if you tested it and it was 0.5, you would assume it was safe. But after getting in the spa, the level has now dropped further, and is below the safe level. Mineral systems are great, but we highly recommend dosing the Sanitizer higher (generally double) of what the product directions call for. Some systems automatically dose the Sanitizer, and that is entirely different, because Sanitizer is constantly being delivered into the Pool and/or Spa. Most of the Frog Systems for Pools and Spas do this, and they are acceptable. One note on the Frog System for Pools. We recommend these for 12,000 or more gallons of water, because they will quickly raise your Stabilizer levels to an unsafe level in smaller pools. For Spas, Bromine is used, so Stabilizer is not an issue (remember Bromine cannot be stabilized). On that note, Minerals are a great addition to pools and spas if used properly.

Optional Products including Ultima® Endure® Water Conditioner

There are many optional enhancement products that can be added to your pool such as liquid solar covers, minerals, etc, however this particular product is unique. While it may be supplementary, we have found it to be one of the best products on the market today. It's compatible with virtually every system on the market, including pools with Chlorine Generators. It's a natural Algae Surpressent, to the degree that most people that use this product, open their pool every year to sparkling clear water. It acts as a clarifier, softens the water, and additionally helps with buffering the pH of your water. We have versions of this product for your Spa was well, labeled under the Leisure Time pH Balance Plus line (the Plus is important, as the pH Balance product is something totally different, and cannot be used in Hard Water). Our favorite part of this product is it lasts the lifetime of the water, meaing you only have to add a small amount occationally to compenstate for backwashing and splash out.

What Systems Do you Recommend

First Time Swimming Pool and Spa Owners

Balancing the pool is going to be closely the same, regardless of what system you are on. Sanitizing and Oxidizing is where our premium chemical systems can help save time and ultimately money in the long run. We have vetrans on our premium chemical systems of over 25 years.


We'll be frank here, many of our customers love it, some do not. Baquacil is a Biguanide based chemical (it actually has a very long scientific name). It has been around for a long time, and the system has been slightly changed to a point where it works great nowadays. One of the biggest issues in the past was keeping the Oxidizer levels high enough, but with the addition of the Step 3: Baquacil CDX, this is no longer an issue. Additional the Algicide was added into the Sanitizer (Step 1: Baquacil Sanitizer and Algicide) because again, many customers choose not to use a Algicide. Biguanides (step 1) are based on many of the same chemicals that surgeons use to wash their hands, and also similar to early Contact Lense solutions. The Oxidizer (step 2) is a strong Hydrogen Peroxide. CDX (step 3) is a very complicated chemical so we won't go into that. And that's it. Baquacil is a Step 1 through 3 system, added weekly, in addition to balancing your water.

The Pro's: Baquacil is the gentlest systems on the market today. It is not dependent on pH levels (although you still keep those levels in check for your pool equipment and surfaces), pH barely plays a role in the sanitizers effectiveness. And Baquacil is one of the easiest systems on the market for new pool owners. Vinyl liners have been known to last for 30 years (where the average for Chlorine is 10 to 12 years with proper maintenance). Biguanide's are one of the only non-chlorine products on the market, which is especially improtant for those people who have sensitivities or allergies to chlorine and bromine.

The Con's: A pinkish buildup will eventually build up in your plumbing, and the use of a Line Clean product is recommended occationally to keep the pool circulating well. Sand should be chemically cleaned at least annually, although some customers choose to change their sand annually (Chemically cleaning of sand should actually be done on every system, but it is especially important on Baquacil). Because this is a premium system, and you are dealing with a large volume of water, Baquacil tends to run about 20-30% more expensive than traditional chlorine systems, although this is the price of piece of mind and reassurance that you are swimming in a safe chlorine free pool..

Baqua Spa

Baqua Spa is only marginally more expensive in spas (about 5%), because you are dealing with a smaller volume of water, that should be changed every 3 months according to industry standards. It still runs on a 3 step system, however CDX is not used, and a Waterline Control product is used instead (the steps run in a little bit of a different order: Step 1: Waterline Control, Step 2: Sanitizer, Step 3: Oxidizer). A number of years ago, Hot Tub Manufactuers started using very cheap plastics for their lighting, etc. and the Hydrogen Peroxide could cause them to crack. The industry has since fixed this issue, and cracking is no longer an issue unless your spa is over 12 years old. Check your spa manual to see if the use of Biguanide voids the warranty in any way, and if not, Baqua Spa is highly recommended.

Pristine Blue (for Pools and Spas)

Pristine Blue is based on copper, and thus should not be used if a sensativity or allergy to heavy metals is present in any swimmers. Pristine Blue is not based on metallic copper, and stays in solution, so with proper maintaince the copper should never come out of solution (see the Alkalinity section). Pristine Blue is added to the Pool every 2 weeks, and of course should be kept balanced. It's a great system. It is compatible with Chlorine, unlike Biguanides, so a Chlorine Oxidizer can be used if there is ever a need (for example: Nitrates). On of the most amazing parts of this system, is it is self dispersing even when the pool's pump is off (because of copper molecules repel each other, and thus spread out throughout the pool).

Chlorine Generators

Let's start by saying a Salt Pool is a Chlorine Pool, which is a huge misconception with Salt Pools. Most new pool owners want a chlorine generator, so we'll focus more on the myths of salt pools.

Myth 1: Salt pools are chlorine free. Salt pools use electrolysis to produce chlorine. You are essentially replacing your 3" tablets with a chlorine delivery system.

Myth 2: Salt pools are easier. Read the balancing section again.. Salt pools require the same balancing as any other system, which most customers find as the most difficult part of swimming pool chemistry. Salt pools produce Sodium Hydroxide (Lye), which is extremely basic (pH of 13.0), so pH has to be more closely monitored and constantly lowered than any other system on the market. Lastly, we have found that the reason Salt pools seem easier, is the pump, and therefore the filter, have to be running for chlorine to be produced. Therefore, most salt pools run longer than any other system. Longer filtration times results in less problems using ANY system, and therefore it is our advice to look into a variable speed pump before investing in salt system (you can do both).

Myth 3: Salt pools are cheaper. While this is not totally a myth, the math only favors salt pools on year round pools. For pools with a 4 to 6 month seasons, traditional chlorine methods are cheaper. Remember, we strongly recommend shocking your pools with a grandular chlorine or non-chlorine shock, so the salt cell itself is really only replacing the 3" Chlorine Tablets. Lastly, the life of a salt cell is governed by the coating on the cell, which is generally Iridium or Ruthenium, and on average will last about 3 years. The cell itself can cost anywhere from $300 to a couple thousand dollars, so many owners choose to go to chlorine after the cell goes bad. This does not even get into the control panel, which as with any electronic device can, and will ultimately need to be replaced (easily a couple grand). Additionally salt cells cannot produce chlorine when the water is at or below 60 degrees fahrenheit (first few weeks and last few weeks of the swimming season), so 3" tabs have to be used to get the pool ready for opening and closing.

Many of our customers love their salt systems, so we'll cover the facts and benefits as well.

Benefit 1: Salt will soften the water, making the water feel soft and overall better.

Benefit 2: As long as their is enough salt in the water and the temperature is above 60 degrees, you don't have to worry about keeping tablets in your water.

Benefit 3 (with some Cons): Many of our customers choose to use the "Super Chlorination" cycle instead of shocking their pool, so they don't have to worry about the Oxidiation step (This is not a true shock, see Oxidiation Section). Also note, this will greatly reduce the amount of salt in your pool, and will reduce the life of your salt cell.

Benefit 4: Salt pools are considered "greener" for a number of reasons, but mainly there is no transportation needs of hazardeous materials (namely Chlorine).

Salt pools have become the most popular system on any Swimming Pool, and we just want to ensure that every customer knows exactly what they are getting, and we believe we covered the most common misconceptions in this section. It might sound like we are against salt pools, but we aren't. Nearly 90% of all new ingrounds we put in use salt.

NOTE: Customers with automatic covers should not use salt generators.

We do however strongly discourage our customers from using salt generators on aboveground pools, even though the aboveground pools we carry do not have a warranty void for their use.

We also do not recommend salt generators for hot tubs, because there are heaters and metallic equipment which can and will corrode. Only a few manufacturers use salt, and it's almost always an "upgrade". Why is it that it's not a standard feature? Ask to see the owners manual for those hot tubs, the warranty, and the cost of replacement before even remotely considering this.

Vetran Pool and Spa Owners

Once you are more experienced with pool and spa chemicals, there are other options to treat your pool and spa.

Bromine for Spas

Bromine is more stable and heavier than Chlorine, so it is highly recommend for Spas, instead of using Chlorine. You don't have to worry about the stabilizer levels building up too fast, bromine is less senstive to pH changes, and because bromine is heavier than chlorine, you aren't overwhelmed each time you open your cover with chlorine gases.

Poolife Brite Stix System

These sticks are your sanitizer, to be used in conjunction with TurboShock (a Calcium hypochlorite, non stabilized shock), and Defend+ Algaecide. The sticks only work in skimmers, as they need running water to dissolve. They dissolve much slower than a traditional 3" tablet, have a built in clairifier and water softener.

Poolife MPT Extra System

This is a better version of the 3" Tablet, and only marginally more expensive. It's used in conjunction with TurboShock (see Brite Stix description) as well as Defend+ Algaecide. The Tablets are a 4-in-1 product, that sanitize, clarify, prevent algae, and soften pool water. These dissolve at the same rate as a traditional 3" tablet.

Poolife 3" Cleaning Tablets

This is a high grade slow dissolving 3" Tablet, and used in conjunction with TurboShock and Defend+ Algaecide.

Poolife 1" Cleaning Tablets

Recommended for smaller pools (such as a blow up pool) to be used in a floater. Essentially the same as their 3" counterpart.

One Last Cautionary Note

This tutorial is designed to inform and educate, but does not serve to replace product labeling or professional pool company or manufacturer advice. Adjust your chemical levels according to manufactuer recommendations, to avoid warranty and safety issues. Always read the product labels and only use products for their intended purposes. If there is ever a doubt, call your professional Pool & Spa Company for their recommendations.

Weekly Service for Swimming Pools & Spas

Some customers just don't have the time, and we get that.

We have one of the largest service departments in the greater Richmond, VA area, and offer weekly maintenance for Swimming Pools & Spas. Call us at 804-748-4330 for more information.

Other customers want us to teach them first

That's absolutely fine as well. Let us know how many weeklies you want to schedule, and that you will want to be there so you can learn. Also ask about our on-site pool school (which is more than enough for most customers). Many new customers schedule either an opening and closing, and a pool school to just get a handle on the basics.

Coming Soon

New Guides
Over the next few months we'll be developing more guides, and possibly break this guide down into different sections. We just felt that a tutorial such as this one is vital for any Swimming Pool or Hot Tub Owner that we couldn't wait. If there is anything you would like to see in the new guides, please contact us and let us know!

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