Help & Advice

You can find in this section technical support guides and information to help you get the best out of your pool or spa. Read our Help & Advice here


Troubleshooting problems in swimming pools and spas. Read our FAQs here

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Water Balance Guide

Before adding swimming pool or spa chemical treatments it is important that you read and familiarise yourself with the workings of your spa / pool and support equipment. Good water circulation and filtration are essential to achieving a safe and clear bathing environment.

Main Criteria Affecting Water Balance

The first step is to ensure good water balance, which will create the right conditions for bather comfort, chemical efficiency and equipment protection. The main criteria affecting water balance are calcium hardness, pH and Total Alkalinity.

Calcium hardness

Hardness is the measurement of calcium salts in the swimming pool or spa water and this will vary depending where you live. Low calcium hardness levels (soft water) can lead to corrosion of the materials of construction. High calcium hardness levels (hard water) often leads to the formation of scale in pipe work and equipment. 

  • Ideal calcium hardness levels are between 250– 500 ppm (mg/l).
  • When the level is below 200 ppm (mg/l), apply OPC Hardness Plus as per the label directions.
  • When the level exceeds 200 ppm (mg/l), apply Spa Range - Scale Inhibitor as per the instructions.


The pH scale has a range of 1 – 14 with 1 being very acidic, 7 being neutral and 14 being very alkaline. It is essential to maintain spa water within the 7.2 – 7.6 range which, being slightly alkaline, will protect equipment from corrosion and provide the optimum conditions for bather comfort and sanitiser efficiency.

  • Ideal pH level for spas is between 7.2 – 7.6.
  • If the pH is below 7.2 use OPC pH Plus as per the label directions.
  • If pH levels exceed 7.6 use OPC pH Minus as per label directions.


pH can be difficult to control in spas as the system water turns over quickly, is highly agitated and operates at higher temperature than swimming pools. All these factors will cause the pH to fluctuate.

As a consequence rises in pH will lead to the performance of chlorine (HOCl) sanitisers to drop dramatically. Much higher doses of chlorine sanitiser will be required. This can be avoided by using Bromine Tablets, Bromine (HOBr) is a highly effective sanitiser, and it is stable over a much wider pH range than chlorine treatments. It is also less volatile than chlorine and will remain in the spa for a longer period reducing chemical usage and ensuring hygienic conditions prevail. 

Buy Bromine Tablets.

Total Alkalinity

Total Alkalinity (TA) acts as a buffer to prevent pH change. If TA levels are too low the pH will fluctuate widely.
High levels of TA will not only affect water clarity, but also make pH adjustments extremely difficult.

  • Ideal TA is 80 - 120 ppm (mg/l) When TA is below 80mg/l use OPC Alkalinity Plus as per label directions.
  • When TA is above 140mg/l use OPC Total Alkalinity Reducer to reduce it as per recommendations on the pack.
  • Water balance should be checked regularly and, certainly, every time you top up or refill your pool or spa. 

Test Strips are available for you to test the water regularly. Buy Water Testers

Click here to find out about ongoing maintenance for your swimming pool or spa.