How to Clean Your Pool Effectively During a Summer Heatwave

When the temperature rises, chlorine burns off. It’s a scientific fact. The burning effect of sunlight means that if you’re not careful, more of the chlorine you add to your water will be wasted, rather than doing the important work of keeping your pool clean and safe. This unfortunate fact makes it essential to use a stabilizer to protect your chlorine and make your supplies last longer.

The Chlorine Problem Starts With The Sun

Many pool owners are aware that chlorine is an essential chemical for keeping pool water safe to swim in. However, few realize how quickly the sun can eliminate it. Free chlorine is very sensitive to direct ultraviolet light; the sun can break down these molecules in a relatively short amount of time – even just a few hours. A study from The Pool & Hot Tub Alliance (PHTA) states that 90% of free chlorine in an unstabilized pool can be destroyed after just two hours of direct sunlight.

Cyanuric acid, also known as stabilizer or conditioner, serves as a barrier between your chlorine molecules and the UV radiation, preventing the breakdown of chlorine. This allows you to stabilize the chlorine level in your pool and reduce the breakdown from sunlight drastically. For reference, a loss of only 25% of your free chlorine is estimated when stabilizer levels are between 30 and 50 ppm.

Test your stabilizer levels at least once a week during heatwaves to ensure optimal performance. If they go too low, you will continue to lose the pool chlorine battle. If they go too high, it can suppress the sanitizer’s effectiveness.

Intensity Varies By Climate

Every heatwave is different. 3-4 hot days in a cooler climate where the norm is 20-25 degrees puts mild stress on a pool. 3-4 weeks above 40 degrees in a Mediterranean-type climate with intense solar radiation is quite a different story. Homeowners in those conditions may want professional support – experts handling pool cleaning perth work in exactly that kind of climate, where sustained summer heat makes calibration and timing far less forgiving than in cooler regions.

Climate also determines how frequently you need to test and adjust. In a temperate zone, weekly checks may be sufficient to keep chemistry balanced. In a hot, sun-drenched region, daily testing during a heatwave is closer to the mark – chlorine demand can spike overnight, pH can drift within hours of heavy use, and stabilizer levels that looked fine on Monday may be critically low by Wednesday. The faster your pool chemistry moves, the tighter your maintenance window becomes.

When And How Long To Run Your Pump

A popular notion is that running your pump overnight saves electricity and offers no particular drawback. In a serious hot spell, however, that innocent bit of water-saving frugality will bite you in the butt.

Run your filtration system for 10 to 12 hours over the course of the day, not at night. First, your sanitizer needs to be in full circulation precisely when the sun is beating down on your pool – the more it moves, the shorter the window where floating debris shields and the sun combine to gobble up your chlorine. Second, extreme heat causes thermal stratification, and your pump running during the day discourages that warm “dead” layer from forming in the top third of the pool.

Shock At Night, Not In The Morning

Applying pool shock, which is a strong dose of chlorine typically made of calcium hypochlorite, to burn off organic contaminants is more of a science than people realize, and timing is everything.

Throwing shock in during the day means the sun’s UV rays start dissipating the treatment before it has a chance to burn off all the microorganisms. If you instead add it post-sunset, the chlorine gets a solid eight hours or so to work through the liquid, germs, and grime without that sunlight-caused interference. Come morning, your free chlorine levels will accurately reflect what you’ve added rather than what the sun has burned off.

Even better: Brush the pool walls, stairs, and bottom, too. Algae doesn’t materialize as a green sheen; it can start as spore-size organisms attached to walls and floors. Scrubbing twice a week, particularly just before applying shock, knocks and exposes those spores to the chlorine swirling around your pool.

Evaporation Throws Off More Than The Water Level

During extremely hot weather, your pool can lose several centimeters of water a week just from evaporation. It’s easy enough to top up, but every time you add fresh water, you’re also adding fresh chemicals from your tap supply to everything else going on in your pool.

When water goes, dissolved solids don’t – they stay behind and become more concentrated, gradually raising your Total Dissolved Solids (TDS) as time goes on. But your water chemistry isn’t going to get more stable just because you’re losing clean water.

For every bit of water you splash in, you’re going to have to re-test and adjust your pH first to keep it between 7.2 and 7.4, because chlorine becomes increasingly ineffective the moment your pH goes above 7.6, regardless of what the test strip still says. Then check your total alkalinity – this will give you an idea of how stable your pH will remain.

And don’t forget that skimmer basket. Because obviously, if the water level drops to where it’s below the skimmer inlet, you’re not going to be skimming anything. That means debris is going to slip to the bottom of the pool, sit there, and rot, consuming your chlorine and adding phosphates to your water.

Staying Ahead Of The Problem

During a heatwave, the goal is prevention not recovery. A green pool takes days to fix and can run up significant chemical costs. A well-maintained pool just needs consistent attention to timing, chemistry, and circulation. Check your stabiliser. Run your pump during the day. Brush twice a week. Shock at night. Top up water carefully and re-test immediately. None of these steps are complicated – they just require doing them at the right time.