Balancing your Pool

When you first set up your pool, the charts supplied with the testing kit recommended that the Alkalinity should be between 100 to 150 ppm, and the Hardness should be between 150 and 200 ppm.

The documentation supplied with the testing kit explained that it was important to adjust the harness and alkalinity of the water before dosing the pool with Chlorine, but did not give any details.

A pool is described as being in balance when the water is neither corrosive nor scale forming. (for the technically minded this is described as the Langelier Index and can be shown in a diagram).

In this case a line drawn through the points 125ppm Alkalinity and 175ppm Hardness gives a calculated saturation pH (pHs) of about 7.55.

This tells us that if the actual pH was 7.55 then the water is "in balance" and is neither corrosive or scale forming.

In a vinyl pool it is recommended that the actual pH is equal to the pHs or slightly less.


This diagram can be very useful to manually calculate the Saturation Index (difference between actual pH and calculated pHs)

(Click here to Print a copy)


Computer Program

to help you balance your pool

"Perfect Pool and Spa" has created a web based software program to allow the test readings to be input and will then produce a report telling you how to achieve a "perfectly balanced pool".


This is not free software but is brought to you courtesy of PoolsiNSchoolZ for any school currently using one of our pools..

To use the software you will require the login and password.

Contact us and we will email the password to you.

Program access:- PerfectPoolandSpa software


- Select your pool from the Pool/Spa List

- Enter the results from your testing (ignore cyanuric acid and Total Dissolved Solids)

- From the red and white box select "Water Analysis"

- Click on View Report or Email if you want to receive a copy.



Diagram from: Pool Water Quality NZS 5826:2010