New Jersey's Leading Pool Service & Repair Company

Basic Pool Chemistry Guide

Understanding your pool chemistry

**All pool chemicals are to be added directly in to the pool water with the exception of Stablizer/CYA**

It is recommended that you add chemicals in increments rather than dumping pounds of chemicals in to the pool at one time. We suggest that you add the chemicals slowly in to the deepest part of the pool or near a pool jet where the chemicals can be easily distributed throughout the pool.

Pool water chemistry is not tricky to master. There are chemicals that you add initially at the beginning of each season (as needed) and then chemicals that you add weekly to maintain. We recommend that you use test strips to monitor your pool levels and visit a local pool store weekly or biweekly to have your water analyzed electronically with a computer.

There are seven main chemicals that you need to be familiar with:

  • Total Chlorine
  • Free Chlorine
  • Algaecide
  • Calcium hardness
  • pH
  • alkalinity
  • Cyanuric acid/stabilizer

Below is a brief overview of each of the chemicals and details what each chemical is, what level you want to maintain, how to raise or lower each level and the effects of letting the levels get too low or high for an extended period of time.

Total Hardness/Calcium Hardness: Calcium hardness is the amount of calcium and magnesium present in your pool.  The ideal range for a vinyl liner pool is between 175-225ppm (parts per million).  Water will naturally have some water of calcium but you typically need to add more in the beginning of the season.  Once there is the initial level establish, this will not alter frequently.  It is important to maintain good calcium levels because the water craves this chemical and if the calcium level is low, the water will pull the calcium from the liner, thus resulting in a shorter life of your liner because the liner will become brittle quickly.  If the calcium becomes too high, then you may see scaling.  To increase your calcium level, you will need to add calcium increaser/calcium hardness.  To lower your calcium levels, you will need to dilute your pool water by draining some (a few inches at a time) pool water out and adding some fresh water.

Total Chlorine: For the lay person, total chlorine is the number of contaminates in the pool.  You want the total and free chlorine levels to be equal, meaning the level of contaminates is matched by the level of sanitizer in the pool.  Total chlorine is the sum of free chlorine and combined chlorine. The level of total chlorine will always be higher than, or equal to, the level of free chlorine. If the total chlorine level exceeds the free chlorine level a super chlorination or “shock” is needed. If the pool water has a strong, offensive odor and is irritating the skin or eyes of the swimmers that may be a sign that you need to “shock” the pool to remove the total chlorine. In short, free chlorine is chlorine that is available and ready to help keep your pool water clean. Combined chlorine has been “used up” and will no longer help with sanitizing your water. Total chlorine is the sum of both the free chlorine and the combined chlorine.

Free Chlorine: Free chlorine is in simple terms the working chlorine in the pool.  In chemical terms, free chlorine refers to both hypochlorous acid (HOCl) and the hypochlorite (OCl-) ion, or bleach, and is commonly added to water systems to sanitize, disinfect, and oxidize.

Combined Chlorine: In simple terms, combined chlorine when the total and free chlorine levels are drastically unbalanced.  When ammonia or organic nitrogen are introduced to the water through contaminants like sweat or organic materials, the chloramines known as monochloramine, dichloramine, and trichloramine will quickly form. Chloramines are also known as combined chlorine.

pH: Is a measurement of how alkaline (basic) or acidic your water is.  Ideally you want your pool pH level to be within the range of 7.0-7.6.  If your pH level is higher than your water is more alkaline/basic.  The lower your pH levels are, the more acidic your pool water is.  Your pH levels will vary slightly throughout the year but this is not a chemical you typically need to adjust weekly.  Rain water is a common reason why pH levels may fluctuate, so after a heavy rain you may need to adjust your levels.

Low pH: Can have damaging effects on your pool.  Since the low pH means the water is more acidic, this means that the water is more corrosive.  Acidic water becomes an issue for heaters because acidic water will strip the copper from the heat exchanger.  Low pH also inhibits the chlorine effectiveness meaning that you may end up spending more than necessary in chlorine and other chemicals.  Lastly, low pH will irritate your skin too.  Low pH causes itchy skin, red eyes and can make your hair more brittle.

To raise your pH, use a chemical called pH Increaser/pH Up (sodium hydrogen carbonate).  To raise you pH level, please follow the directions on the chemical container or from your local pool store as chemical adjustments will vary.

High pH: High pH is an issue you would want to avoid as well.  High pH can result in scaling or other mineral deposits, cloudy water and inefficient sanitizing.  The skin and eyes can also be irritated from high pH as well because the human body is close to neutral on the pH scale.

To lower your pH, use a chemical call pH Decreaser/pH down (sodium carbonate).  Check the container or with your local pool store for the amount to add to your pool.

Total Alkalinity: Total alkalinity measures the amount of alkaline substances (primarily bicarbonates and carbonates) in your water.  Alkaline substances buffer your water against sudden changes in pH so that your water chemistry is more easily controlled.   Without a proper alkalinity level, your pH can fluctuate drastically and frequently.  You want to maintain levels of 80-125ppm (part per million).  Alkalinity can be raised by adding alkalinity increaser in to the pool.  This is not a chemical you necessarily need to add weekly but will tend to need after a heavy rain.  Since alkalinity is closely tied to pH levels, alkalinity increase naturally increases pH slightly and pH decreaser will also lower your alkalinity levels.

Cyanuric Acid (CYA)/Stabilizer: Cyanuric acid does not affect your water chemistry or balancing of each level, but is used rather as a “sunscreen” for your sanitizer.

Algaecide: Algaecides are used in conjunction with your sanitizer to prevent algae from growing in your pool.  Algaecides are sold as weekly treatments and 90-day/3-month algaecides.  Algaecides vary in strength and this will affect how much you need to add to your pool.  We recommend using a copper based algaecide.  The copper based algaecides tend to be the 90-day and 3-month algaecides.  These algaecides are stronger because of the active ingredient (copper).  Algae cannot grow with copper, thus giving you the best fighting chance against algae.  *Please note that copper is safe for your pool in small amounts but must be monitored*.

Clarifier**: Clarifier is not necessarily a chemical but more of an addition that you may want to use to give your water a sparkle.  A clarifier should only be used for pools with sand or cartridge filters; a D.E. filter filters down to 3 microns and therefore does not need a clarifier.  A pool clarifier will coagulate or group up the particles so that the filter can filter out extra debris.  While natural claifiers are more expensive, we recommend natural clarifiers because they are safe to swim with and are safe for even the newest pool owner.  A natural clarifier is safe if you mistakenly overuse it, however with a clarifier that is not natural, overusing may result in the reverse effect and actually cloud your water.



HIC REG#13VH07598400

5420 Route 9 South
Howell, NJ 07731

Phone Number:
(732) 905-1300

We’re open Monday – Friday, 9 a.m. – 5:30 p.m. EST

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