What’s the Best Time to Close Your Pool for Winter?

We’ve all seen it happen. The days get shorter, temperatures drop and the kids spend more time on their laptops than swimming in the pool. It can only mean one thing – summer’s over. 

If you’re a seasoned pool owner, it means unpacking your winter cover, finding that bottle of algaecide and putting your pool into hibernation mode. But if you’re new to pool ownership or you’ve never winterised your pool before (and suffered the consequences!), you may not know when to start winding things down. Should it be the last day of summer? The first day of winter? When temperatures drop below 18 degrees? 

Truth is, there are no hard-and-fast rules. It all depends on where you live, how much you swim and whether you have a pool heating system. However, you can still work out the best time to close your swimming pool based on a few different factors.

But before we dig in, let’s take a look at what winterising is and why it’s so important for your pool.

Why you should close your pool for winter

Swimming pools get a lot of use during the warmer months, particularly if you live in a warm climate. But as the days get cooler, you may find yourself abandoning the pool in favour of other pursuits, like playing Wordle in front of the heater or watching Netflix in bed. 

In the meantime, your pool may fill up with debris and rainwater, and pool maintenance may fall by the wayside. By the time spring comes around, you’ve got cloudy pool water, unsightly stains and clogged filters. This means hours of cleaning and shocking – or worse, a hefty bill from the pool technician!

The best way to avoid this inconvenience is to close your pool for the winter. But that doesn’t mean slapping on a cover and turning off your equipment. Instead, it involves reducing filtration, using winterising chemicals, covering your pool and keeping an eye on your water balance and equipment. 

Not only do these measures keep the water sanitised and debris-free, but it also protects your pool equipment from damage (and we know how expensive linings and pumps are to replace!). Plus, it minimises the use of pumps, heaters, cleaners and chemicals. This can lower operating costs and minimise the time you spend on your pool. That’s right. No more eye-popping bills in winter, or skimming the pool in freezing weather!

Factors to consider before you close your pool

Now that you know why winterising your pool is so important, let’s look at the factors that determine when you should close your pool – or whether you should close it at all.

Climate

Winter temperatures in Australia vary, depending on where you live. Whether you’re in chilly Hobart, tropical Cairns or temperate Adelaide, your climate zone will affect when or if you decide to close your pool. If you have daytime temperatures in the mid-twenties in winter, then you’ll probably want to use your pool all year round. If you have a short or mild winter, you may want to wait until June or July before closing your pool, depending on your comfort level.

If you live in cool or temperate zones, temperatures will drop considerably during autumn and winter, which means that your pool will get less use. As a result, it’s a good idea to start closing it in April or May. Even if you have a pool heater and want to keep your pool open, keep in mind that water will take longer to heat up and use more energy. Plus, water temperatures higher than 28 degrees Celsius can promote algae and bacteria, which can eat up your sanitiser and result in green pool water. So if you want to keep your pool toasty in winter, increase your sanitiser and keep an eye out for algae.

Location

Outdoor pools are readily affected by temperature fluctuations and inclement weather. If your pool is in an exposed area and you get frequent rain, frost or snow, it’s best to close your pool before these conditions arise. Even tropical areas experience a wet season between December and March, so you may want to protect your pool by closing it or using a sturdy cover. 

Indoor pools aren’t as affected by low temperatures or debris as outdoor pools, so you may not need to close them in the cooler months. In fact, you can use them all year round and your heater won’t have to work as hard to keep the water warm. However, if your pool is only partially enclosed with a tarp or glass roof, the temperature of the water will still drop and it may benefit from a late-season close. 

Usage

Despite weather conditions, you may want to keep your pool open all year round. Maybe your kids are training for the swim team. Or you like to unwind after work by doing a few laps. Whatever the reason, it may not be practical to close your pool. If you have a heating system and you don’t mind paying higher energy bills, your pool can be kept open all year round. 

However, if you’re planning to go away for a few weeks or months, it’s worth closing your pool and setting up automations to keep the filtration and chlorination running smoothly. You can even get a friend or relative to check the water balance from time to time and adjust it accordingly. This could save you the headache of coming home to a cloudy or leaf-ridden pool!

Environmental debris

Autumn means one thing – leaves. When you have a pool, it can fill with leaves pretty quickly, particularly if you’ve got a lot of trees or you live near bushland. This can lead to hours of skimming and cleaning, not to mention scrubbing stains (leaves are notorious for staining pool surfaces) and rinsing out blocked filters. 

To avoid the hassle, it’s best to close your pool, at least until the leaf drops have subsided. If you decide you want to swim in your pool in July, you can open it up again. Alternatively, you can keep it closed to lower costs and prevent overworking your pool heater.

Budget

If you’re like most people, you may love your pool in summer but hate the bills in winter. Let’s face it, stormy weather and cool temperatures can make winter pool maintenance more expensive. You need to run the cleaner and adjust chemicals after a downpour, as well as ramp up your heat pump to make the water comfortable (particularly if you get low overnight temperatures). It also gets darker earlier in winter, which means you’ll be using more lights if you’re swimming in the early mornings or evenings, increasing your costs further. 

If you’re budgeting or you want to reduce running costs, close your pool from mid-autumn to early spring. Even though your pump will still be running, it’ll be at a lower capacity, and you’ll need less sanitiser to keep the water clean. 

Can you close your pool too early?

While closing your pool saves time, energy and money, doing it too early can be detrimental to your pool. If you can, wait until daytime temperatures are less than 18 degrees Celsius. There are two important reasons for this. First, winterising chemicals may deteriorate faster in warm water and won’t last until spring. This could leave you with unbalanced water – or spending more on chemicals than you should. 

Second, algae loves warm water, so if you’re still getting temperatures in the low twenties in mid to late autumn, they’ll multiply a lot faster, particularly if your pool is covered and filtration is reduced. Instead, wait until the temperature drops further, and use the recommended amount of winterising chemicals. When combined with fortnightly water testing and balancing, this should keep your water sanitised and clear throughout winter.

How to close your pool for winter

Whether you’ve got an inground or aboveground pool, it’s important to close it correctly. Here’s our easy, step-by-step guide to closing your pool for winter (or any time of the year).

Step 1: Give it a deep clean

Using a pool brush, scrub the walls and floor of the pool to remove any scum, algae or stains. Don’t forget the steps and around the light fittings. When you’re done, run your automatic cleaner to pick up the debris and vacuum the pool thoroughly. 

Step 2: Clean the filters

It’s a good idea to clean your filter before closing your pool, even if you did it recently. This will ensure that debris won’t get lodged or re-contaminate the pool water. If you have a pool cartridge filter, remove it from the housing and give it a good rinse with a hose. Check for damage and give it a deep clean with a filter cleaner if required. For more details, check out How to Clean a Pool Cartridge Filter. If you have a media filter, backwash it for 2 minutes. If the water still looks dirty, run it for another 2 minutes until it runs clear. 

Step 3: Balance the water

Now it’s time to get your water balance right. Use a water testing kit to test the chemical balance or take a sample of the water to your pool shop. Based on the results, adjust your chlorine, pH, alkalinity and calcium hardness to achieve the right water chemistry. Shock the pool if necessary. 

Step 4: Add winterising chemicals

Winterising chemicals are used to keep algae at bay. Start with adding Zodiac Phosphate Remover. Phosphates increase in your pool after excess rain or when environmental debris isn’t immediately removed. If left untreated, it can provide food for algae. Next, add Zodiac Pool Long Life Algaecide. This will both treat and prevent algal growth while your pool is closed. 

Step 5: Use a cover

Not everyone likes the look of a cover on their pool, but it’s the best way to protect your pool in winter (and summer, for that matter!). Not only does a winter pool cover reduce evaporation of water and chemicals, but they also stop debris from throwing off the water balance or clogging up your filter. However, if you get a lot of rain or even snow, keep an eye on your cover to make sure it doesn’t sink in the middle. A winter mesh cover or solid automatic cover should withstand these conditions, but a thermal or solar cover may not be resilient. In that case, use a water pump to remove the water from the top or invest in a tougher pool cover.

Step 6: Reduce operation of your pool pump

Because your pool is not being used, you won’t have debris like sweat, urine, sunscreen, dog hair or leaves wreaking havoc on your pool water. Plus, your pool cover will prevent the evaporation of water and sanitiser. This means your pump and filtration system won’t have to work as hard to keep your pool clean. Instead of running your pump for 6–8 hours a day, drop it to 4–6 hours, depending on the size of your pool.

Step 7: Monitor every two weeks

This is a crucial step. While you’re not keeping up the same maintenance schedule as you would in summer, you still need to check your pool. Every two weeks, make sure your equipment is functioning properly. Empty the skimmer baskets and check the filter gauge in case a backwash is needed. Adjust the water level if it’s too high or too low. Remember, if the water line is below the skimmer recess, your filter won’t be able to keep your pool water clean and it may damage your pump. To prevent this, install an automatic pool water leveller to top up your pool when necessary. 

Last, test the chemical balance of the water and adjust as necessary. But don’t worry, you won’t need as much chlorine or balancing chemicals in winter because the pool is covered and it’s getting little use. However, it’s still important to keep sanitation levels within the recommended range to avoid nasty surprises in spring. 

TOP TIP: If you want to avoid the hassle of adjusting chlorine levels during winter – or beyond – consider installing a salt chlorinator. Some chlorinators, like the eXO iQ pH Salt Chlorinator also monitor and adjust your pH balance.

Final thoughts

Knowing the right time to close your pool comes down to a few things: where you live, how cold it gets, how often you use your pool and your budget. If you live in a zone with cool winters, it’s best to close your pool when daytime temperatures drop to less than 18 degrees. That’s because the pool is less likely to develop a nasty algae problem under these conditions, particularly if you use a winter algaecide as a preventative measure. 

If you choose to keep your pool open, keep in mind that heating costs may increase due to low ambient temperatures, and that you’ll need to continue your weekly maintenance schedule. However, if you’re on a budget, closing your pool can minimise your use of chemicals and reduce energy consumption, allowing you to save a few hundred dollars each year.

Ready to close your pool for winter? Then contact one of our approved dealers to stock up on winterising chemicals, or browse our Sunbather winter mesh covers to keep your pool debris-free. Alternatively, go back to our pool and spa guides for more winterising tips.