• By Andrew Astonville
• Published 02/29/2012

While swimming pools make for hours of fun during the summer months, it is essential to maintain them with the correct chemicals if you want crystal clear pool water that is free of harmful bacteria.

There are two main priorities when treating your pool so that it remains free of bacteria – sanitisation and correct water balance.

The following easy guide will give you the key steps to take to ensure your swimming pool is both beautiful and safe for use.

Sanitisation

Sanitisation amounts to keeping your pool water free of bacteria. While granular chlorine is the most commonly used chemical for maintaining a healthy, clear swimming pool, there are various other alternatives you can use, such as sodium hypochlorite (liquid chlorine), chlorine tablets, salt water chlorination and UV chlorination. You can also opt for using Ozone or bromine.

Do take the time to discuss these various alternatives with your local pool shop or pool service, to find the one that will suit your needs best.

Balancing Your Swimming Pool Water

Maintaining the correct chemical balance of your pool water is vital. Here are the key factors you need to know about to do this effectively:

pH

The pH of your pool water is of utmost importance – in a nutshell, it is the means of measuring its acidity or alkalinity levels. This needs to be done as if these levels are imbalanced it can have serious effects, from causing your eyes to sting to damaging the pool’s structure. The pH needs to be regularly monitored as it will also determine how effective your sanitising agents are at destroying bacteria.

The pH values range from 0 which is highly acidic to 14 which is highly alkaline. The perfect pH is neutral, measuring at 7.0 pH, which is neither overly acidic nor overly alkaline.

Using a specialised tester, if your pool water is too acidic you will need to add an alkali which will allow the pH value to rise. Conversely, if the water is too alkaline, add an acid to drop the pH. It’s important to note that most of the chemicals used for treating swimming pools are either acid or alkaline based, which will in turn affect the pH.

Summary of the damage caused by an imbalanced pH:

A low pH in your pool water (below 7) can cause eye and skin irritation plus corrosion of the heater elements and other metal fittings. The latter in turn causes stains on the walls, which results in loss of alkalinity and thus causes the water to become acidic.

Too high a pH value (above 8) causes chlorine to be inefficient, making the water cloudy. In addition, the swimming pool filter can be choked by this, causing it to overwork. Eye and skin irritation may also occur, as well as the formation of scale and stains on the walls.

Total Alkalinity (TA)

Total Alkalinity is an essential test when treating your pool. It measures the amount of alkaline substances in your pool water and prevents pH changes by stabilising the pH levels.

Bicarbonate alkaline is the important factor in TA and should be kept at 80 – 120 ppm (parts per million).

To raise the TA without adversely affecting pH levels, use sodium bicarbonate. It can however be a fairly slow process as this chemical can only be used every four days at the rate of 1Kg for 50,000 litters of water.

To lower the TA, add an acidic chemical (whether in liquid or dry form) to the deep end of the pool, making sure the filter is turned off. The acid should be diluted, then added to the water slowly. This process is also fairly slow since the acid can only be added every three days and it can take many weeks to reduce the TA. You can calculate the quantities of acid needed using a pool calculator.

Summary of the damage caused by an imbalanced TA:

A low TA can cause your pool’s walls and floor to become etched and stained, as well as effecting random pH changes plus making eyes burn and the water turn green.

A high TA makes adjusting pH levels difficult, resulting in more frequent additions of acid needed. It can also cause the water to become cloudy and causes chlorine to lose its efficiency in the sanitisation process.

Calcium hardness

Calcium hardness is the amount of calcium dissolved in your water and is important in preventing the concrete, grout and metal fittings of your swimming pool from being dissolved.

Ideally your pool water should be between ‘medium’ and ‘hard’ – the concentration of calcium in the water should be a minimum of 80 ppm and a maximum of 150 ppm.

In hard water areas, pools generally naturally have a high calcium content, so calcium would rarely need to be added.

Total Dissolved Solids (TDS)

TDS are the dissolved substances in your pool resulting from chemicals, water evaporation, soluble pollution from people and sanitisation by-products. If the TDS in the water is too high, it can cause corrosion of the swimming pool and affect the efficiency of chlorine sanitising agents.

TDS can be measured using a specialised TDS meter. Total dissolved solids should be maintained at less than 1500 ppm and if they are above this reading, you will need to drain some of the pool water and replace it with fresh water.

Conclusion

As can be seen from the above guide, swimming pools must be given the appropriate tests and maintenance on a regular basis to ensure the water is both attractively clear and safe for swimmers.

About the Author: Andrew Astonville is an independent advisor on maintaining swimming pools.