Pool Chemicals

Without regular sanitisation, all pools develop bacteria which can pose serious health risks to swimmers. Top-up water, leaves, grass, dust and swimmers all cause bacteria to grow. These factors, along with the size of your pool will determine the level of sanitisation you need.

Most pool owners use chlorine. There are other options to keep pool water clean and in balance, such as using ozone gas, UV sterilisation, bromine or ionisation. But these methods occupy a very small slice of the Australian market. Health Departments around Australia generally recommend all domestic pool owners have a chlorine residual in their pool. Check with your local health department to confirm the requirements in your state.

There are three main ways domestic users can keep their pool chlorinated.

• By hand – which involves adding chlorine manually.
• Installing a salt chlorinator – which produces chlorine and is the most common form of domestic pool chlorination in Australia.
• Installing a liquid chemical feeder – which automatically adds chlorine.

Chemical Balance

In addition to sanitisation, you also need to chemically balance your pool water. The chemical balance of your pool is made up of:

• pH (acidity/alkalinity level): 68%
• Total Alkalinity (TA): 16%
• Calcium hardness: 16%

You should monitor your chlorine and pH levels at least once a week or every day if your pool is in high use. Total Alkalinity and Calcium hardness levels can be monitored less frequently.

Balancing PH

Maintaining the pH level of your pool is critical to providing a safe environment for swimmers. Incorrect pH levels can cause itchy skin and red eyes. It can also reduce the effectiveness of chlorine.

PH ranges from 0-14, with 7.0 being neutral, above 7.0 alkaline, and anything below 7.0 acidic. The Australian Standard for pool water is 7.0 to 7.8, with 7.4 being ideal.

Rain, water top-ups, swimmers and chlorine will all alter your pool’s pH. PH levels can be raised by adding soda ash (which is alkaline) or lowered by adding acid.

Total Alkalinity (TA)

Total Alkalinity is the measure of bi-carbonates, carbonates and hydroxides in your pool water. Low levels will cause erosion to pool surfaces and corrosion of equipment. It can also cause pH levels to become very unstable.

The Australian standard recommends that your TA level should be 60 to 200 parts per million. You can raise the TA level by adding 'buffer' – sodium bicarbonate – or lower it by adding acid. Bear in mind, adding acid will also affect your pH levels.

Calcium hardness

Low levels of dissolved calcium in pool water can corrode pool equipment and high levels can create scale. Calcium hardness levels can’t be monitored using most domestic pool water testing kits. Instead you need to take a sample of your pool water to your local pool shop for testing. In areas where calcium levels aren’t high, you shouldn’t need to do this test more than once a year – unless you use calcium hypochlorite to sanitise your pool.

Testing kits

There is a wide range of kits on the market which you can use to test your pool water – from simple strips to sophisticated electronic units.

A basic 'Four in One' test is a good starting point. This basic kit tests chlorine levels, Total Alkalinity, pH as well as the level of acid needed to rebalance the pH. These cost around $33. Alternatively, you can now buy electronic testers, which will analyse a disposable strip that you dip in your pool. These strip readers cost around $100 and additional packets of 50 strips costs around $19.

Chlorination

Manual chlorination

The most labor intensive way of keeping your pool sanitised is to manually add chlorine as it’s required. This involves testing your pool’s water and adding the required amount of chlorine. This may appeal to people who are renting a property with a pool and aren’t looking for a long term solution.

The average backyard pool will need additional chlorine every second day – and this can be added in liquid, granular or tablet form.

Salt chlorinators

Salt water pools are popular among Australian pool owners – but they don’t do away with the need for chlorine. Salt water pools use salt chlorinators to convert common salt crystals into chlorine gas which is soluble in water. You can install a salt chlorinator into the existing pipe work of any kind of pool. The only exception is above ground pools with metal structures - as they will rust.

Salt chlorinators use an electrolysis process to turn salt into chlorine gas which in water forms Hypochlorous acid – this is what disinfects your water. The size of salt chlorinator you need will be determined by:

• The size of the pool
• The environment, for example weather and leaf load
• Bathing load
• Temperature of the water

Your chlorinator should be able to cope with your pool’s maximum bathing load. So if your child’s basketball team is planning to come over regularly, factor that into your calculations. Also consider your climate. A pool in tropical North Queensland will have different chlorine requirements to a pool in suburban Melbourne.

There are two kinds of salt chlorinators – those that are self cleaning and those that aren’t. If you don’t buy a self cleaning model, you will need to manually clean the salt from the cell. This could be required as frequently as every fortnight. Self cleaning models don’t require this intensive maintenance but they are more expensive.

When a salt chlorinator is initially installed, you will need to add salt to your water. The recommended initial dose is 4kg of salt per 1000 litres. This is no where near as high as the salt levels in the ocean. The electrolysis process doesn’t consume salt but 20 to 30% will be lost every year due to backwashing, splashing and overflow. Periodic salt top-ups will be needed.

Salt chlorinators operate automatically — so you can go on holiday, knowing your pool water will remain safe. They are also cost effective to run. The ongoing costs of an average domestic pool with a salt chlorinator should be around $10-15 a month.

The initial cost of a salt chlorinator ranges from $600 to over $2000. You can expect them to last for around 5 years — but eventually they will wear out because the electrolysis process is sacrificial. This means the cell is gradually consumed by the electrolysis process.

The capacity of a chlorinator is generally expressed in grams per hour. Some pool suppliers will express a unit’s capacity in terms of its liquid, granular or tablet chlorine equivalent. As a guide, liquid chlorine is about 12 to 15% chlorine, granular chlorine is about 65% chlorine and tablets can be up to 100% chlorine.

While salt chlorinators automatically put chlorine into your pool, you still need to monitor and adjust the pH, Total Alkalinity and Calcium hardness.

Liquid chemical feeders

Liquid chemical feeders are fitted to your pool’s filtration system and automatically add liquid chlorine, and in some cases, acid to the water. The simplest models only inject chlorine into your pool – the amount and frequency will be programmed by you. These units start from around $600.

More sophisticated models have a sensor probe which automatically tests the chlorine and pH levels of your pool every few minutes. They then inject chlorine and/or acid to keep the water clean and balanced. This means that if 10 people jump into in your swimming pool, the feeder will automatically inject more chlorine.

These models start at around $2000, plus there will be the ongoing costs of liquid chlorine and acid.

Even though the more sophisticated models monitor and adjust pH levels, it’s still recommended that you regularly test the levels yourself.

Verdict

Which chlorination system will suit you?

• If you have the time or aren’t looking for a long-term solution, manual chlorination may suit you.
• Although the initial set up costs are high, salt chlorinators can be a convenient and economical option over time, because they generate their own chlorine.
• With liquid chemical feeders, there's no cost-saving in terms of chemicals over time. But the chemical balance of your pool will be steadier.