How To Fix A Green Pool

Walking out to a green pool is one of those moments every Perth pool owner dreads. The water has turned green, the walls look slimy, and your weekend swim plans are finished. We see this every week across the northern and southern suburbs, and for several reasons it happens faster here than almost anywhere else in the country. Perth’s hot weather, bore water loaded with phosphates and the sun’s uv rays create perfect conditions for algae growth that can turn a swimming pool from clear to swamp in under 48 hours.

The good news is that a pool water green situation is fixable. We have been recovering green pools since 2003 and the process is the same whether it is a light green tint in Scarborough or a dark green pool in Ellenbrook where you cannot see the bottom of the pool. This guide walks through how to fix a green pool using the method we follow on every job. If you need it done for you, our green pool recovery service covers all of Perth.

Why Does A Pool Turn Green

There are several reasons a pool can turn green, and it is rarely just one thing. The most common reasons we find on callouts across Perth are low chlorine levels from a failing salt cell or missed dosing, a filtration system that is not running long enough, and phosphates feeding algae spores that are always present in the water.

In the warmer months from November through March, Perth pushes above 35 degrees regularly. At those temperatures, algae doubles every few hours and a pool can turn green overnight. If your chlorine levels drop below 1 ppm and your pool pump is only running six hours a day, you do not have enough chlorine circulating to keep up. We serviced a pool in Wanneroo last summer where the owner had been buying shock treatment from the local pool store and dosing weekly. The pool kept turning green. When we tested, the sand filter had channelled so badly it was pushing algae particles straight back into the water. No amount of pool chemicals fixes a broken filter.

Bore water from the Gnangara Mound is the other factor unique to Perth. It carries phosphates, iron and minerals that feed algae. If you are topping up from a bore without running a phosphate remover, you are giving algae exactly what it needs. Heavy rain makes this worse by diluting sanitiser and washing contaminants in, which is why pools often turn green after rain.

How To Fix A Green Pool Step By Step

Every green pool fix we do follows these steps. The severity determines timing, but the process does not change.

Test A Water Sample

Start with a water sample. We test on site for free chlorine, ph level, alkalinity, stabiliser, phosphates and copper. You can also use test strips from your local pool store, but a professional water test results reading gives you the full picture. Copper is worth checking because it can turn water green without any algae present, and most pool owners do not test for it.

Skim, Brush And Remove Debris

Before adding any chemicals, remove leaves and floating debris with a skimmer net. Clean out the skimmer box and pump baskets. Then brush the pool walls, pool floor and every pool surface to dislodge algae clinging to grout lines and pebblecrete. If you skip this step, the visible algae embedded in surfaces survives the chemical treatment and grows back within days. We use a stiff bristle brush on pebblecrete and a softer nylon brush on fibreglass to avoid surface damage.

Adjust The Chemical Balance

Get the chemical balance right before shocking. If ph is above 7.8, chlorine loses most of its killing power. We adjust ph level to between 7.2 and 7.6 and alkalinity to 80 to 120 ppm. This is the step most DIY attempts skip, and it is the reason the right chemicals do not work when the balance is off.

Shock The Pool With Chlorine

We dose with liquid chlorine because it raises levels immediately without adding stabiliser. If your pool uses a salt chlorinator, check the salt level too and add salt if it has dropped below the manufacturer threshold. In Perth, where cyanuric acid builds up fast from years of granular use, liquid chlorine is the better option for shock dosing. The appropriate dosage depends on severity. A light green pool might need double the normal dose. A dark green pool where you cannot see the floor needs five times or more. We keep dosing until chlorine holds above 10 ppm overnight, which confirms the algae is dead.

Run The Filtration System Continuously

After shock treatment, the pool pump and pool filter must run nonstop for 24 to 48 hours. This is what clears the dead algae and debris from the water. We check the cartridge filter or media filter pressure gauge and backwash or clean as needed. On a heavy green pool recovery, we may need to backwash or clean the filter two or three times during this phase. A dirty filter just recirculates the problem.

Vacuum And Clear The Pool Floor

Once the dead algae settles to the bottom of the pool, vacuum it to waste so it does not pass back through the filter. Use the waste setting on your multiport valve and vacuum slowly across the floor. Then brush the walls again to rid the surfaces of anything left behind. After vacuuming, clean the filter one more time.

Retest And Rebalance

After 48 hours of circulation, take another test. Chlorine should sit between 1 and 3 ppm, ph level between 7.2 and 7.6. If everything holds, the fix has worked. If chlorine is still dropping overnight, there is residual algae and you need another round of shock treatment. For a faster approach to less severe cases, see our guide on how to fix a green pool fast.

Preventing Your Pool From Turning Green

Eliminating algae is one thing. Keeping it gone requires regular maintenance. We recommend testing and adjusting chemicals weekly, brushing walls and vacuuming the pool floor fortnightly, and running the pump long enough for at least one full water turnover per day. During hot weather and the warmer months, increase pump run times and check chlorine twice a week.

Use a pool algaecide preventively during summer, not just as a fix. A phosphate remover every few months cuts the food source, especially if you are on bore water. Keep the skimmer box and pump baskets clear so circulation stays strong. These small steps prevent algae growth before it starts and help you avoid pool water problems down the track. For more prevention tips, read our green to clean pool top 7 tips.

When To Call Us For Green Pool Recovery

If you have tried to fix a green pool and it keeps coming back, or the water is so far gone you cannot see the floor, it is time to get professional help. Persistent green pool water often points to equipment issues, a dead salt cell, worn filter media, or a circulation problem that chemicals alone cannot solve. If your pool turned green overnight or looks green and cloudy, there is usually an underlying cause beyond just low chlorine. There are also health risks with prolonged exposure to untreated water, including eye irritation and bacterial infection, so do not swim in it until it is sorted.

We handle everything from the water chemistry to the equipment diagnosis. We have recovered pools across Perth that other services could not fix, including one in Baldivis where three rounds of DIY shock treatment had failed because the pump was only circulating water through half the pool due to a blocked return line.

If your pool has turned green and you want it fixed properly, get in touch with our team. We test, diagnose and fix the problem so your swimming pool gets back to a crystal clear state and stays that way. No guesswork, just results from a team that has been doing this across Perth for over twenty years.