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Do I Need to Winterize My Pool?

Cooler weather is upon us, and you may be asking yourself, “Do I really need to winterize my pool?” The short answer is, it depends. Your location plays a big role in answering that question. In fact, some people in the far south regions of the U.S. may not ever have to worry about closing the pool at all. That said, there are risks involved with that approach, as there are also risks associated with improperly closing a pool.

Now for the next question, “What happens if I don’t close my pool?” The answer here: a lot can happen! In this post, we’ll explore the worst case scenarios that may occur with an unwinterized or improperly winterized pool, including:

pool filter

Cracked Equipment

pool plumbing valve

Burst Pipes

cross section of a pool

Structural Damage

Leslie's Acid Wash pool services

Stains & Scale

pool algae outbreak

Algae Blooms

As you see, there are so many things that can happen to a pool over the winter. Let's take a closer look at why it's important to close and maintain a pool through the cooler off-season months.

Cracked Equipment

If you’ve ever wondered why it’s so important to winterize the pool correctly, we can sum up the biggest reason in two words: freeze damage. As water freezes, it slowly expands to an area that’s 9-10% larger than its non-frozen liquid state. If your equipment is full of water, as you can imagine, freezing temperatures are bad news. The building pressure from that expansion has to go somewhere. Parts of your pool equipment will often crack under the added stress. Pool pump housings, heater headers, and filter tanks are just a few examples of the costly damage a freezing spell can cause to your equipment pad.

DIY TIP: If your plumbing or equipment is down for the count, you'll need to find other ways to maintain the pool until you can make repairs. We have all the information on how to do this in our other blog post, "How To Maintain a Pool With Damaged Equipment." It's the only post we hope you never have to read, and for obvious reasons.

Burst Pipes

As mentioned above, freezing water expanding in a contained area spells disaster. When it comes to your pool’s plumbing, the risks of damage are just as high as with your equipment. The time and cost of repair really depends on the location of the damage. If the pipe is exposed, it won’t take too much extra time, effort, or money to replace the cracked section of plumbing. However, if the damage happens underground, you’re looking at a more intensive and costly repair in the near future. Which brings us to our next point …

Structural Damage

Severe freezing weather conditions can sometimes cause underground water lines to burst. Once the lines thaw, water begins seeping into the surrounding area and draining from the pool. At first, it may not seem like a huge deal. Maybe your pool equipment can’t function as efficiently as it used to. Or maybe you find yourself refilling the pool more often thanks to a "hidden leak." Eventually, you may notice a chronic wet spot near your inground pool. You might even notice your deck and pool walls developing severe cracks as the ground starts to shift. When this happens, it’s time to call your pool contractor and get your checkbook ready. Ideally, you’d be able to fix the leak before it becomes a bigger problem with the pool itself. But realistically, undetected slow leaks in underground plumbing lines can – and do – happen.

Structural damages are also a very real concern for above ground pools. Without the help of an air pillow to break up the layer of surface ice, freeze expansion presses outward on the pool walls. With enough pressure, weakened spots in the wall will split and/or crumple like a soda can. If there’s a leak below the ice layer, shifting ice will ruin your vinyl liner if not also destroy the pool wall. 

Stains & Scale

Beyond protection against freeze damage, the second most important reason for closing a pool correctly is to prevent stains and scale on pool surfaces. Closing a pool with poor water balance or debris in the water guarantees a difficult pool opening in the spring. You’ll spend hours getting rid of floor stains and scrubbing away scaly waterline buildup when the cover comes off. Either that, or you'll be hiring a professional to acid wash your pool.

If you leave your pool open, you’ll (hopefully) be keeping up with routine cleaning, water balance tests, and chemical adjustments, anyway. But on the off chance that you need to perform an emergency pool closing, unbalanced water in a dirty pool will set you up for trouble when you reconnect your equipment.

Algae Blooms

Algae is probably the last thing on your mind during the winter months. Besides, algae can’t grow well in colder temperatures … right?! Yes, this is true. However, an improperly closed or poorly maintained pool can absolutely turn green by the time you’re ready to open the pool, even under a cover.

Once you close the pool, check sanitizer levels monthly to make sure your pool can fight off algae. If you live in the sunbelt or experience a period of 60ºF or higher temperatures, you may need to test your winterized pool more often. Add a quality winter algaecide at closing time, keep your floating sanitizer dispenser full, and occasionally shock the pool with non-chlorine shock to oxidize contaminants and free up available chlorine.

DIY TIP: If severe winter weather is in the forecast and you haven't closed your pool yet, don't panic! It's possible to do an express winterization. Learn how to close your pool quickly – with or without power – in our blog post, "How To Respond to Freezing Weather Conditions."


Most pool owners should take the time to correctly winterize and close their inground or above ground pool for the off-season. Clean and balance the pool, disconnect and drain all pool equipment, and purge the lines before adding a pool cover. When severe winter weather strikes, pool owners who already closed their pool can be confident that their pool is safe. 

In areas where temperatures seldom drop below 60ºF, you may not want to close the pool because of increased risks of algae growth. Pool owners in this situation may choose to leave the pool open (with or without heat) or just partially close the pool for the winter. However, partial closings or open pools face an increased risk of damage when unexpected winter weather strikes. Automatic freeze protection works wonders, but even this extra layer of protection has a chink in its armor.

Take, for example, the Texas winter storms of 2021. When unusually low temperatures and winter storms gripped the area, the power grid went down. Suddenly, the freeze protection measures pool owners had in place were rendered useless. Without circulating water, lines froze, equipment cracked open, and pools throughout the region saw a significant and costly level of damage. The moral of this story is that you should always have a “plan B” if you intend to leave your pool equipment running this winter. Familiarize yourself with emergency winterizing procedures, and be prepared to take action if necessary.

If you have any questions about winter pool care or pool closing procedures, we're here to help! Call or stop by your local Leslie's store to speak with one of our friendly pool experts.

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