7 reasons why algae keeps coming back

I've noticed a recurring request recently from commercial pools experiencing a return of green algae in the pools even when chlorine levels are high and algaecide is used.

here is a list of what I believe are the most common culprits in no particular order and will OFTEN BE A COMBINATION OF TWO OR MORE

1. low chlorine with high ph - chlorine works more effectively at lower ph values e.g 1 ppm of chlorine will have more killing power at 7.2 ph than 1 ppm at 7.8

2. high stabilizer levels - high levels especially near or above 100pm will overprotect the chlorine and prevent it from sanitizing and oxidising. your test kit will still read a good amount of chlorine is present but high stabilizer slows down chlorine considerably.

3. pool filter age and condition - if the pool filters allow the algae spores to pass through then they will remain suspended in the pool and with other contributing factors multiply faster than if they are collected on the filter media. Additionally when the pool usage slows down in the fall there are longer periods between backwashing/filter cleaning where fresh makeup water is added. Poor circulation will show the most algae growth in 'dead spots' around the pool.

4. heated pools - heated water does not create algae growth by itself but it does speed it up. I have noticed more algae complaints after the heaters have been turned on for the fall/winter season.

5. phosphates and nitrates - steroids for pool algae and sometimes introduced when fertilizer is used nearby and blown in. This plant food feeds the algae like eating fast food 3 times day.

6. pool surface - as the pool gets rougher the algae spores can find places in cracks, pitted areas and pop offs

7. High TDS - Total dissolved Solids (TDS) which is made up of all the minerals, used chemicals and funk in your pool which makes the water cloudy and gives the algae a place to hide.

BRUSHING

daily or weekly brushing is the least fun activity in pool maintenance but I have found it to be be the cheapest and fastest way to reduce and eliminate green algae growth

for solutions use the items listed above as a remedy checklist and/or contact your local experienced and licensed commercial pool for service and chemicals

please add useful info with your comments below