How to Maintain Swimming Pool Water - Part 1

It’s all about the water.  In order to make your pool look inviting, you need to keep the water crystal clear. 

You do not have to be a chemist in order to maintain the water quality in your pool.  However, you should understand the components that make your pool water safe and ideal for swimming.   The components are tested based on a parts per million (ppm) measurement.  This is the measurement of the parts of a substance in relation to one million parts by volume of pool water.

How to Test Swimming Pool Water

Using the test strips from the pool supply store should be sufficient for testing.  Get the strips that show the chlorine, alkaline, pH, and cyanuric acid.  Find an area away from the skimmer and the returns and with the strip in hand submerse about 18 inches into the water for about 10 seconds.  Remove but don’t shake water off.  Wait a few moments until the colors fill in.  Compare each component’s color reading to the color range on the product bottle. (Read the instructions that were provided with the test kit as this procedure could vary from product to product).


The pH balance of your water impacts the effectiveness of the chlorine in your water. The idea test reading for pH is between 7.4 and 7.6.  If the test reading is below 7.2 then the water is more on the acidic side. A test reading above 7.8 indicates the water is more on the alkalinity side.  Monitor the pH daily using test strips.


To keep bacterial, pathogens, and algae from growing in your water, the chlorine (sanitizer) level needs to be at a safe level for swimming.  A chlorine test reading between 1.0 and 3.0 ppm is optimal.  If you use bromine tablets instead of chlorine as the sanitizer, then the reading should be between 2.0 and 4.0 ppm.  Ask your pool store for more advice on the pros and cons of using bromine instead of chlorine, or if you want to switch over to bromine from chlorine or visa versa.  Monitor the chlorine level daily using the test strips


The alkalinity reading should be between 100 and 120 ppm.  Typically goes hand in hand with pH.  If the alkalinity reading is low, then most likely the pH reading is low and visa versa.  Typically chlorine shock contains alkaline which will help raise the alkaline level.  On the flip side of that, chlorine tablets which contain cyanuric acid tends to lower the alkalinity.

 Cyanuric Acid

The cyanuric acid (chlorine stabilizer) reading should be between 20 and 30 ppm. This component is usually a product of chlorine tablets.  It slows the escape/evaporation of chlorine which in turn helps to maintain a more consistent chlorine level.  However, since chlorine tablets contain this component which is an acid, it tends to lower the alkalinity and the pH.

Safety Considerations

Consideration to keep in mind when dealing with pool chemicals:

  • Always follow the manufacturer’s instructions and warnings as indicated on the label.

  • Don’t mix any chemicals together.  Add each separately to the pool.

  • Wear protective safety glasses and avoid breathing in vapors when applying.

  • Store chemical in a cool, dry, and shaded area out of reach of children and family pets.

How to apply pool chemicals

If your pool is sanitized using chlorine chemicals, then the two primary applications you’ll want to use in your pool are chlorine shock (I like the granular shock that is package in 1 pound bags) and the chlorine tablets (I prefer the 3 inch tablets that you add to the chlorinator).

If your pool is sanitized with a chlorine generator system that produces chlorine from salt added to the pool, then you won’t need to add chlorine chemicals at all. You just need to add salt occasionally to the pool and adjust the main control unit to increase the amount of chlorine release.  Ask your pool installer or pool supply store for advice on this. 

Baking soda (sodium bicarbonate) is an idea ingredient for raising the alkalinity and the pH.  Other products like pH Increaser and Alkaline Increaser are available at the pool supply store.

Adjusting Pool Water After Pool Opening

When you first open your pool, you should get the system running before adding the initial dose of sanitizer via chlorine shock.  However, if you have a chlorine generator, you only need to add salt to the pool so you can skip to the the Adjusting the pH and Alkalinity section.

If applying chlorine shock, then for example: a 16’ by 32’ pool which is about 20,000 gallons, one pound of shock should raise the chlorine level to 2 ppm.  You should probably add 2 pounds to kill all the bacteria and get the level to 4 ppm.  After this you may need to add more if the chlorine level doesn't rise to the appropriate level. I would not add any more shock for at least a day or two after the initial dose.  Also wait about two days before adding the (chlorine or bromine) tablets to the chlorinator.  Otherwise your chlorine level may be too high.  Also, do not add (chlorine or bromine) tablets to the skimmer basket.  Doing so will reduce the life of the pool pump and filter.  Getting the chlorine to the correct level after pool opening can be tricky.