Pool Chemistry

Thinking of the perfect swimming pool and visions of sparkling water and happy swimmers likely dance in your head. Keeping this scene intact involves taking the proper steps to sanitize the pool and prevent any health or aesthetic problems. The water will then remain clear of algae, free of disease causing pathogens and users won’t complain about red eyes or chlorine smell.

For general pool treatment, chlorine has three essential characteristics: it acts as a rapid and persistent sanitizer, an effective algaecide and a strong oxidizer of undesired contaminant. Understanding the role of chlorine in maintaining safe water is not difficult once you learn the basics of pool chemistry.

Pool Size and Depth

The size and depth of the pool you select should be based on how you want to use the pool. If you just want to get in a cool off then a smaller pool will be sufficient. If you like to entertain large groups of people or want to be able to swim laps then you will need a larger pool.

The term Play Pool refers not to the size of the pool but the depth of the pool. A typical Play Pool is 3’ in the shallow end and 5’ in the deepest part of the pool. A Diving Pool will be 8’ to 10’ deep in the deepest end. Pools are measure by perimeter and surface area. For example: A small pool would be 15’ x 25’ would have a perimeter of 80 ft, a surface area of 375 sq ft and approximately 8,000 gallons based on 3’x4’x5’ depth.

Basic Steps for Pool Treatment

Carefully read and follow the manufacturer’s instructions printed on the chlorine treatment package. Test the water regularly—it’s a simple process to use a test kit. You want to maintain water balance by measuring:

  • Free available chlorine (FAC), which should be in the range of 2 – 4 ppm, but never fall below 1.0 ppm
  • Total chlorine, to assure that combined available chlorine (CAC) levels are less than 0.2 ppm
  • The pH level to keep it between 7.2 and 7.8, indicating that the chlorine is working effectively
  • Total alkalinity to make sure that pH levels stay steady
  • Calcium hardness to protect pool surfaces from corrosion.

Pool Shapes

When designing your backyard it is important to consider the shape of the pool. The shape of the pool will set the entire design of the area. Here are the basic shapes but don’t be afraid to mix designs together to come up with a unique shape.

Straight Line

Also known as Geometric, this pool shape utilizes straight lines and/or geometric curves. This doesn’t have to be your basic rectangle but can have multiple angles and curves to create a timeless design that will look great 10 years later. One popular style that utilizes this type of shape are Grecian or Roman designs inspired by Old World Europe.

Free Form

Free form swimming pools use curves and flowing lines to mimic nature. This shape looks amazing with the addition of natural rock boulders, grottos and waterfall features. If you are looking for a tropical paradise then this is the shape for you.

Negative Edge

An infinity edge pool, also called negative edge, zero edge, infinity pool, disappearing edge, or vanishing edge pool, is a swimming or reflecting pool that produces a visual effect of water extending to the horizon, vanishing, or extending to “infinity.”

Wet Edge

A wet edge swimming pool incorporates the negative-edge look but differs in that the design allows water to spill over all four sides. Like the negative edge design, the water that flows over the sides of a perimeter-overflow pool is collected in a hidden catch basin and recirculated. This look gives the illusion that the water is level with the deck.

Pool Chemicals – How Much of What?

The guidelines set by The Association of Pool & Spa Professionals are widely used, but to be certain, you should also check the health codes of the jurisdiction where you live. The chemicals a pool needs to maintain the required standards differ from pool to pool—and day to day. Keeping records to “get to know” a pool can help you interpret its characteristics and perform the correct task.

The Association of Pool & Spa Professionals

Suggested Chemical Standards for Swimming Pools

Free Chlorine, ppm 2.0 – 4.0
Combined chlorine, ppm None
pH 7.2 – 7.8 (ideal range of 7.4 – 7.6)
Total alkalinity, ppm

  • For liquid chlorine, cal hypo, lithium hypo
  • For gas chlorine, dichlor, trichlor and bromine compounds
80 – 100

100 – 120

Total dissolved solids, ppm Not to exceed 1500 greater than at pool start-up
Calcium Hardness, ppm 200 – 400
Cyanuric acid, ppm 30 – 50