From murky green to crystal clear.
A green pool is a stalled asset — unusable, deteriorating, and harder to recover with every warm day. John Brennan Pools restores algae-bound pools to clinical clarity, usually within days. Every recovery is overseen by Principal Technician John Brennan, drawing on over 25 years of hands-on pool industry experience.
Why pools turn green — and why it matters.
Green water is algae, and algae is a symptom of chemistry left to drift. Inadequate filtration, low sanitiser, and organic debris let it bloom. Left alone it multiplies fast — staining surfaces, clogging equipment, and creating a genuine health risk.
Health Risks
Green water harbours bacteria and pathogens, posing a genuine risk to swimmers — particularly children and pets — and poor visibility is a drowning hazard in its own right.
Equipment Damage
Algae buildup bonds to pool surfaces and clogs filtration systems, leading to costly repairs and resurfacing if left unaddressed.
Pest Breeding
Stagnant green water rapidly becomes a breeding ground for mosquitoes and other unwanted pests around the property.
A green pool is rarely just bad luck — it's chemistry that's been left to drift. Catch the drift early and you never see green. — John Brennan, Principal Technician
The longer you wait, the more it costs.
Every day of delay makes recovery harder and more expensive. Algae multiplies quickly, building a thick layer that bonds to surfaces and chokes filtration. Acting fast protects both your equipment and your family from waterborne illness.
Monitor your water for early signs, treat any green tint immediately, and call a professional the moment the problem persists.
John Brennan Pools runs a rapid-response recovery service, so your pool is returned to clear, safe water without the wait.
Six warning signs your pool needs attention.
If you recognise these in your own pool, the algae has likely already taken hold.
Visible discolouration is the clearest sign algae has established itself.
Strong smells point to imbalanced sanitiser or organic breakdown in the water.
Weak circulation lets algae settle and spread across surfaces.
Drifting chemistry is the root cause behind most blooms.
Organic load feeds algae and rapidly consumes available sanitiser.
A slick surface means algae is already firmly established.
If you've spotted one of these, you've usually got two or three. Best to have it looked at properly. — John Brennan, Principal Technician
What a green-pool recovery actually involves.
Recovery is methodical, not magic. John Brennan Pools begins with professional water testing and balancing to read the chemistry, then corrects the underlying cause before clearing the colour. Most pools are back to clear water within days.
Because the practice fixes the fault rather than masking the symptom, the pool stays clear long after the visit — not just until the next warm week.
How John Brennan Pools revives a green pool.
Over 25 years of hands-on experience, refined into a proven sequence. Every step restores the pool efficiently — and stops the problem returning.
Comprehensive Assessment
We test water chemistry, inspect equipment, and identify the underlying cause of the algae bloom.
Shock Treatment
The pool is dosed with the correct sanitiser to eliminate algae and bacteria — initiating the transformation.
Deep Clean
Specialised vacuuming and brushing of walls and floors removes debris and algae buildup from every surface.
Filtration Service
We inspect and service the filtration system to ensure proper circulation and water quality going forward.
Balance & Monitor
pH, alkalinity and sanitiser levels are adjusted and monitored until the pool is fully balanced and safe.
Prevention Plan
We provide tailored maintenance recommendations so the green never returns.
Severe or long-neglected pools may need additional visits — John will tell you honestly what's involved before any work begins.
There are no shortcuts with a green pool. You fix the cause, not just the colour. — John Brennan, Principal Technician
Effective treatment. Safe for your family.
John Brennan Pools uses biodegradable, family-safe products wherever possible — minimising harsh chemicals while still clearing algae completely. The practice also favours water-saving methods and energy-efficient, variable-speed equipment, so effective recovery doesn't come at the planet's expense.
A professional assessment and tailored treatment, follow-up maintenance to prevent recurrence, and eco-friendly products wherever practical.
Preventing future green pools.
Staying clear is about consistency. Test pH, alkalinity and sanitiser weekly; skim and vacuum to remove the debris that feeds algae; keep filters clean; use a cover when the pool is idle; book routine professional servicing; and act the moment you notice a faint tint.
Weekly water testing. Balanced water simply won't grow algae — everything else is back-up.
For the full picture, read our guide on why pools turn green and how to prevent it.
The Johnson residence.
Their pool turned a murky green after a winter of neglect. The John Brennan Pools team assessed it quickly, ran the full recovery process, and had the water back to its original clarity within days — ready for summer.
The Smith residence.
Repeated algae despite the owners' best efforts. A thorough inspection traced it to underlying filtration faults; once those were corrected, the pool stayed clear — beautiful and safe for good.
Any pool can be brought back. The real work is making sure it stays back. — John Brennan, Practice Lead
Green pool questions, answered.
What causes a swimming pool to turn green on the NSW Central Coast?
A pool turns green when algae bloom in water with imbalanced chemistry — typically low or inconsistent sanitiser combined with poor filtration and warm conditions. On the NSW Central Coast, John Brennan Pools most often traces green water to a chlorinator or filtration fault, a long gap in maintenance, or heavy rain and debris diluting sanitiser levels. Left untreated, the algae multiplies quickly and begins to stain and damage pool surfaces.
How long does it take John Brennan Pools to fix a green pool?
John Brennan Pools restores most green pools to clear water within a few days, depending on how severe the algae bloom is and the condition of the filtration system. A lightly green pool can often be corrected in 24 to 48 hours, while a heavily neglected pool with thick algae may need several days of treatment, cleaning and filtration cycles. The practice identifies the underlying cause on the first visit so the pool does not simply turn green again.
Is it safe to swim in a green pool?
No — swimming in a green pool is not safe. Green water harbours bacteria, algae and other pathogens that pose a genuine health risk, particularly to children and pets, and the poor visibility is also a drowning hazard. John Brennan Pools recommends keeping everyone out of the water until the pool has been professionally treated, rebalanced and confirmed safe.
Should I try to fix a green pool myself or call a professional?
A faint green tint caught early can sometimes be corrected by a pool owner with a shock dose and balanced chemistry, but an established green or black-green pool should be handled by a professional. John Brennan Pools uses correct sanitiser dosing, commercial cleaning and filtration servicing to clear algae fully and address the root cause — guesswork and repeated retail chemical purchases usually cost more than a single professional recovery.
Can a green pool be saved without draining it?
Yes — most green pools can be recovered without draining. John Brennan Pools clears the vast majority of green pools through shock treatment, brushing, vacuuming and filtration, keeping the existing water. Draining is a last resort reserved for extreme cases such as long-abandoned pools or severe staining, because a full drain risks structural damage to the pool shell and is far more costly.
How can I stop my pool from turning green again?
The most reliable way to prevent a green pool is consistent water chemistry, clean filtration and regular professional servicing. John Brennan Pools recommends testing pH, alkalinity and sanitiser weekly, running the filter long enough each day, and booking routine maintenance to catch problems early. After every recovery, the practice provides a tailored prevention plan so the same conditions don't return.
The water-care library.
Uncompromising StandardsDon't let a green pool compromise your summer.
A free quote, a rapid response, and over 25 years of experience restoring Central Coast pools to clinical clarity. Owner-led, fully licensed and insured — no call centres, no upselling. Because your pool is an investment, not just a backyard feature.
Written by John Brennan
John Brennan is the Practice Lead and Principal Technician of John Brennan Pools, a specialist pool and spa practice serving the NSW Central Coast since 2019. As Principal Technician, John brings over 25 years of hands-on technical experience — across QLD, the NT and NSW — in diagnostics, clinical water chemistry and asset preservation. As Practice Lead, he sets the clinical standards every technician on the team is trained to meet, so every engagement is delivered with the same master-level care.
Green-pool recovery is one of the most diagnostic jobs in the trade: the colour is only the symptom, and a lasting fix depends on reading the chemistry and filtration correctly. John's recovery process is built to resolve the underlying cause — not just clear the water for a week — so the pool stays safe and balanced long after the visit.
Fully Licensed & Insured · ABN 11 202 829 652 · Contact John
References & Standards We Follow
John Brennan Pools treats and balances water with reference to recognised public-health and water-chemistry standards:
- NSW Health public pool water-quality guidance — bacterial, pH and disinfectant benchmarks for safe swimming water.
- Water balance (Langelier Saturation Index) — the framework for keeping water neither corrosive nor scale-forming.
- Manufacturer dosing specifications — correct sanitiser and chemical dosing for the pool's volume and surface.
- Chemical Safety Data Sheets (SDS) — safe storage, handling and dosing of all treatment chemicals.
This page offers general guidance only. Always defer to current NSW regulations and accredited professionals for your specific property.
Across the Central Coast.
Full pool servicing across 90+ suburbs — from Umina to Lake Munmorah and everywhere between.