What to Do With Your Pool After Rain in Brisbane (And How to Survive the Wet Season)

Nash Moores
May 25
5 min read

A solid afternoon storm can dump 50mm of rain in an hour and while your lawn loves it, your pool does not...

The good news is that rain damage to pools is almost always fixable. The bad news is that if you ignore it for a few days, a straightforward rebalancing job can turn into a green pool recovery! Here's what to do, when to do it and what to expect through the wet season.

What Rain Actually Does to Your Pool

Rain looks clean, but from your pool's perspective it's a problem on several fronts.

It dilutes your chemicals. Every litre of rainwater that enters your pool reduces the concentration of chlorine, salt and other sanitisers. After a heavy Brisbane downpour, your chlorine levels can drop enough to make the pool unsafe within 24 to 48 hours.

It throws off your pH and alkalinity. Rainwater is naturally acidic. When it mixes with pool water, it pulls your pH down and destabilises your total alkalinity. Low alkalinity then makes pH harder to control, which makes chlorine less effective, which makes algae growth more likely. It compounds quickly.

It brings in phosphates. Runoff from your garden, lawn and surrounds carries phosphates into the pool. Phosphates are essentially fertiliser for algae. High phosphate levels are one of the main reasons pools go green after wet weather even when chlorine looks fine on paper.

It dumps debris. Leaves, dirt, insects, grass clippings and whatever else was sitting around your yard ends up in the pool. Organic debris consumes chlorine, straining your sanitiser levels further.

It can overflow the pool. Brisbane storms can add enough water to raise pool levels above the skimmer box, which means the surface skimming system stops working. Floating debris just sits there and starts breaking down.

What to Do Right After a Storm

You don't need to jump in immediately while it's still raining. But once the weather clears, work through this in order.

1. Check the water level

If the pool has overflowed or is sitting above the skimmer box opening, lower the water level before doing anything else. You can do this by setting your pump's multiport valve to "waste" and running it until the water drops back to the midpoint of the skimmer box. Don't drain more than necessary and never fully drain a pool.

2. Skim and vacuum

Remove surface debris with a skimmer net, then vacuum the pool floor. If there's a lot of silt or fine dirt on the bottom, wait 24 to 48 hours for it to settle before vacuuming and vacuum to waste rather than through the filter to avoid clogging it. Clean your skimmer baskets and pump basket while you're at it.

3. Test the water

This is the step most people skip and then regret. Testing your water after rain tells you exactly what needs to be added and how much. The key things to check are:

Chlorine (should be 1 to 3 ppm for chlorine pools)
pH (should be 7.2 to 7.6)
Total alkalinity (should be 80 to 120 ppm)
Calcium hardness (should be 200 to 400 ppm)
Salt (if you have a salt water pool, rain dilutes salt levels too)
Phosphates (especially after heavy storms with garden runoff)

You can bring a water sample into our pool shop and we'll test it for free!

4. Rebalance your chemicals

Work in this order: alkalinity first, then pH, then chlorine. Adjusting alkalinity first makes pH easier to stabilise and stable pH makes chlorine work properly.

After a big storm you'll often need to shock the pool, which means adding a higher dose of chlorine to quickly kill off any bacteria or early algae growth. Run your pump continuously for at least 8 hours after shocking.

5. Run your filter

Don't turn the pump off and walk away. Keep it running to circulate the chemicals and filter out fine particles. After a storm, run it for at least 12 to 24 hours. If the water looks cloudy, a pool clarifier can help bind fine particles together so the filter can catch them.

The 48-Hour Rule

If you can test and rebalance your pool within 48 hours of heavy rain, you'll almost always avoid serious problems. Leave it longer than that, especially in Brisbane's summer heat and you're giving algae ideal conditions: warm water, diluted chlorine and a feed of phosphates. Once algae takes hold, you're looking at a green pool recovery rather than a simple rebalance.

Two days. That's the window.

Brisbane's Wet Season: What to Expect From November to March

A single storm is manageable. Brisbane's wet season is a different challenge. From around November through to March, you can expect regular heavy rain, high humidity and temperatures that rarely drop below 25 degrees overnight. That combination is hard on pools.

A few things change during wet season worth knowing about:

You'll use more chemicals. The combination of frequent rain diluting your water and warm temperatures accelerating algae growth means your pool needs more product through summer than it does in winter. This is one reason Pool Wizard separates chemical costs from service fees. Your pool might need significantly more product in January than in July and you should only pay for what it actually needs.

Phosphate levels need more attention. After every decent storm, phosphates come in from the garden. Testing for and treating phosphates through the wet season is worth doing regularly, not just when you notice a problem.

Your pump needs to run longer. In winter you might get away with running your pump 6 to 8 hours a day. Through summer, 10 to 12 hours is more appropriate for Brisbane conditions. More circulation means better filtration and better chemical distribution.

Weekly checks become important. A fortnightly service schedule works fine for many Brisbane pools through winter. Through the wet season, some pools genuinely need more attention. If you're on a regular servicing plan with us, talk to your technician about whether your frequency suits the time of year.

Watch the water level constantly. Heavy rain weeks can see your pool overflow multiple times. Check it after every significant event.

When to Call Someone

Most post-rain maintenance is DIY-able if you have a testing kit and basic chemicals on hand. But there are situations where it's worth getting a professional out:

The pool has gone green. If it's already green, a DIY approach often takes longer and costs more in chemicals than a professional treatment. Our green pool service is $400 plus the cost of chemicals used.

You're not sure what the water needs. Guessing at chemical adjustments can make things worse, not better. A proper water test takes the guesswork out.

The pool has been neglected for more than a week during wet season. The longer it goes without treatment, the more work is involved to recover it.

Something looks wrong with the equipment. Storms occasionally cause damage to pool equipment, especially if the yard flooded. If your pump sounds different or your chlorinator isn't behaving normally after a storm, get it checked before assuming the water chemistry is the problem.

A Word on Pool Covers

If you don't have a pool cover, wet season is the time you'll wish you did. A good cover won't completely stop chemical dilution during heavy rain, but it significantly reduces debris and phosphate load. It also reduces evaporation and helps hold heat, which reduces heating costs if you run a heater. Not essential, but worth considering if you're doing this every summer.

Need a Hand?

Pool Wizard services Brisbane's southside, Redlands, and Bayside. Whether you need a one-time post-storm service ($125 plus chemicals), a regular servicing plan or a green pool recovery, we're upfront about pricing and happy to help you work out what your pool actually needs!

Request a service here or call us on 0435 588 331.

Pool Wizard is a Brisbane-based pool servicing company and pool shop, servicing homes across Brisbane's southside, Redlands and Bayside.