What causes a pool to turn green ?
A green pool is usually caused by an algae bloom. Algae are naturally present in the environment and can quickly multiply when pool conditions allow.
Why does algae grow?
Algae need very little to thrive. If your pool loses its sanitiser or water circulation for even a short period, algae can begin multiplying rapidly, especially during warm weather. Once established, it can spread throughout the pool in just a few days.
Some of the most common causes include:
Low chlorine levels – The most common reason. Without enough sanitiser, algae are free to grow.
Poor filtration or equipment failure – A faulty pump, clogged filter, broken chlorinator or equipment that isn't running long enough reduces water circulation and sanitisation.
Neglected pool maintenance – Skipping regular cleaning or water testing allows algae to establish before it's noticed.
Hot weather – Warm temperatures speed up algae growth and increase chlorine consumption.
Heavy rain or storms – Rain can dilute your pool chemicals while introducing dirt, phosphates and other nutrients that encourage algae.
Poor water balance – Incorrect pH or other unbalanced water chemistry reduces the effectiveness of chlorine.
Organic debris – Leaves, grass and other organic matter provide nutrients for algae and increase chlorine demand.
Alex’s Advice💡
Regularly checking your pool equipment is one of the easiest ways to prevent unexpected algae growth. I recommend checking your equipment once every fortnight during winter and once a week during summer, when warmer temperatures make algae grow much faster.
A quick equipment check only takes a few minutes:
Check your pump is running correctly – During operating hours, look through the clear lid or viewing glass on your pump. You should be able to see water flowing through the system, which confirms that your pump is circulating water properly.
Check your filter pressure gauge – Your filter pressure should normally stay below the halfway mark on the gauge. If the pressure rises too high, it usually indicates that the filter is becoming blocked. A clogged filter reduces water circulation and filtration efficiency, creating the perfect conditions for algae to spread.
Clean your pump and skimmer baskets – Full baskets can restrict water flow, reducing the performance of your filtration system and potentially causing your pump to run under strain or fail. Poor circulation can quickly lead to water quality problems and a green pool.
These simple checks can help you identify small issues before they become expensive repairs or a major algae outbreak.
If you have any concerns about your pool or equipment, feel free to get in touch. I’m always happy to help with advice or answer any questions.
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