Why does my water test show no sign of Chlorine in my pool?
Test result can vary depending on the time of day that the test sample is taken and from where in the pool it was taken. It is best to take the sample directly from the outflow (where the chlorinated water re-enters the pool) and at the end of the equipment's running cycle. It should be 0.5 ppm higher at the outlet than elsewhere in the pool.
The display on the chlorinator's power supply will indicate the output of chlorine.
If an algaecide containing benzalkonium chloride has been added to the pool within the last 3-4 weeks, this compound reacts with chlorine until it is all gone, leaving a nil chlorine reading. To overcome the addition of Benzalkonium Chloride, you may need to manually add chlorine, preferably liquid chlorine to obtain a free chlorine reading again. As guide, about twenty (20) litres will be required.
It is preferable to add a copper-based algaecide (eg. copper sulphate) to treat an algae problem, as it does not affect the chlorine in the water.
Check that your running times are set correctly to suit the time of year. As guide:
- Summer running times are 10-14 hours per day, preferably at night when the sun is off the pool.
- Winter running times are 4-8 hours per day, prefered at night when the sun is off the pool
- If solar heating is installed, some running times will need to be set to operate during sunlight hours.
- N.B. Off-peak electricity hours in Sydney are from 10pm until 7am.
If a sand filter is installed, has it been backwashed in the last month? Has the sand been changed in the last 5 years? With regular backwashing, the edges of the sand become rounded and do not filter as effectively over time. Therefore, the sand will need to be changed about every 5 years. A good way to check if your filter is filtering properly is to hold a sample of the pool water in a clear glass up to the outside light. If you can see 'floaties', first try backwashing the filter several times, for 3 minutes each turn. If there are still 'floaties' after several turns, then the sand will need to be changed.
Also check your pH is within the correct range (7.2-7.8). Within this range, chlorine is more effective as a sanitiser, as there is a higher percentage of hypochlorine acid (HOCI) in the water.
A simple rule we follow is... if the pool is clean and clear and sparkling, leave it alone!