How to Winterize a Pool

how to winterize a pool 1

How to Winterize a Pool

Winterizing your pool is an important step in taking care of your pool to ensure you can enjoy your pool for many swim seasons to come. 

The winterizing process varies widely depending on your climate. Warm climates tend to leave their pools operational over the winter, while cold climates require you to completely shut down and cover the pool.  I wrote this guide to cover everyone, regardless of your climate. 

What climate am I?

Some locations have obvious answers to this question, but many locations do not. I recommend talking to other pool owners and pool stores in your area to see what is common practice in your area. 

If your winters typically include several consecutive days where your daytime highs remain below freezing, I recommend following the cold climate section of this guide. 

Warm Climates – How to Winterize an In-ground Pool

Winterizing a pool in warm climates is significantly easier than your cool-season counterparts, but you still need to take steps to ensure your pool and equipment are protected from the winter. 

In general, the biggest defense against freezing water in warm climates is to ensure your pump is running when air temperatures approach the freezing point and remains running and circulating the water until the temperature is safely above the freezing point. 

Freeze Guards On Your Automation System

Many modern pools have automation systems that are essentially mini-computers near your pool equipment that allow you to control your pool remotely, manage your schedules, and have built-in freeze guards. 

Pictured below is a Pentair Intellicenter/Easy Touch which is the most widely used automation system, but all of the major equipment manufacturers have similar automation systems that serve the same purpose. 

If you have an automation system, they do most of the work for you if they are set up properly.  However, that does not mean that it can be completely hands-off.  I recommend each fall you check your settings to ensure that the freeze guard is turned on for your pool or pool/spa combo. 

You can see the screenshot below from the Pentair Intellicenter interface, and the Spa and Pool circuits have the freeze guard functionality turned on properly. 

In this setup, the automation system would turn on and cycle between the pool and spa modes to ensure that all pipes have water running through them regularly when the temperatures drop below freezing. 

Waterfalls and other features should also be included in the freeze protection if they have pipes that will be full of water and at risk of freezing.  The downside to this is that running these may also collect ice on the surface of the water features.

You have to look at the equipment pad and piping to your water feature to determine what is best for your pool.  If it can be turned off using a valve at the equipment pad and allow water to drain to the portion of the piping underground, that may be your best option. 

Other Types of Freeze Guards

I have talked a lot about automation systems, but many pools do not have the fancy automation systems but that does not mean they cannot handle freezing weather. 

The best option is that your timer has a freeze guard and a temperature probe to measure the air temperature so that it knows when to turn your pool on and off. 

If your timer does not have a freeze guard, check your pump as it may have built-in freeze protection. 

What If I Do Not Have a Freeze Guard?

If you do not have a freeze guard on your equipment, fear not, people were able to successfully protect their pools from freezing for decades before all of the freeze guards were even invented. 

If this is the case, you simply need to turn on your pump so that it is running during freezing temperatures.  If you have frequent nights that dip below freezing, I recommend changing your pool pump schedule to run overnight so that you will be protected even if you forget to check the forecast and turn on the pool before bed. 

What Else Do I Need To Do To the Pool in the Winter?

You still have to maintain your pool in the winter.  Winter maintenance can be more involved than your normal schedule during the swim season depending on your leaves. 

In the winter, I recommend checking and emptying the skimmers daily.  On some windy days, that may need to be more frequent. 

You also need to make sure you are running your cleaner regularly, which may be more often than during the swim season. 

Lastly, you still need to maintain your proper chemical levels.  Algae typically do not multiply once your water temperature drops below 60, but you still need to maintain proper chlorine levels. 

Another level to watch in the winter is your calcium level if you have an in-ground plaster or pebble pool.  As the water temperatures drop, water tends to be more aggressive if your calcium is low and can dissolve the calcium from your plaster into the water. 

A final note for salt water pool owners.  In the summer your pools make their own chlorine, but once the pool temperatures drop to below 50-55 degrees Fahrenheit they stop working.  For these times you need to make sure you are monitoring and adding supplemental chlorine to maintain your chlorine levels. 

Contingency Planning

Everything I have described above assumes that your pool has electricity and is working properly.  Unfortunately, in 2021 many people in Texas and the Midwest found out the hard way that all of the fancy freeze protection is useless if you have no power and temperatures are abnormally cold. 

Here is what I recommend doing if you find yourself in freezing temperatures without power or working equipment:

  • Flip the breaker to the pool equipment so that it does not try to run when the power is restored.
  • Drain all of your equipment including your pump(s), filter, and heater. Each of these will have 1 or more plugs at the bottom for quickly draining the water out of the equipment.
  • Open up all valves, pump basket lids, and anything else that will allow the remaining water in your system to expand if it freezes without breaking anything.
  • Cover the equipment with a tarp to help retain heat and prevent any trapped water from freezing.
  • Protect your skimmers by adding cut-up pool noodles to absorb the force of the ice as it freezes and expands.  In a pinch, empty plastic water bottles with the lid on tightly in the skimmer can accomplish the same thing. 

Most importantly, make sure you know how to do all of the above well before freezing temperatures hit.  You do not want to be out there at 2 A.M. with a flashlight and freezing temperatures trying to locate your drain plugs. 

FAQ – Warm Climates

Can I cover my pool?

Yes you can.  Covers can make your life easier if you have lots of trees.  Just make sure you can monitor the water level, empty the skimmer, and add chemicals since you will still need to do that in the winter.    

Can I ignore my pool during the winter?

No, in fact, winter maintenance may be more regular than your maintenance during swim season.    

Can I use my attached spa during the winter?

Yes, as long as your pool equipment is working properly enjoy your spa.  I use mine at least weekly during the winter. 

Should I turn on the heater when it is going to freeze?

I do not recommend this as heaters are not designed to cycle on/off during freezing temperatures and prolonged cycling can cause excess condensation within the heater and shorten the life span. 

If you do decide to use your heater before a freeze, make sure you set the pool temperature high enough to avoid your water from reaching that temperature and cycling on and off. 

Cold Climates – How to Winterize a Pool


In cold climates that receive much lower temperatures, it is just not practical to leave your pool operational during the winter months.  Therefore, you need to close your pool for the winter. 

While the closing of your pool is much more involved than your warm climate counterparts, your winter maintenance is much less involved after you close. 

When Do I Close?

Algae growth begins to slow down once the water temperature drops below 60-65 degrees.  I recommend waiting until your water reaches this temperature before you begin closing. This will lessen your chances of opening in the spring to a green pool that needs to be cleaned.

Step 1: Preparation

Now is a good time to check your winter cover, check your pool supplies, review the closing steps and obtain anything you need to winterize your pool. 

Step 2: Clean-up time

Once you decide today is the day to close your pool, your first step is to ensure you have a clean pool.  Remove all of the leaves, give your pool a good brushing, and remove any ladders, stairs, and other accessories from your pool. 

Step 3: Adjust your chemicals

Next, you want to adjust all of your chemicals to make sure that your pool remains balanced while it is closed. 

  • Bring your pH down to 7.2-7.6.
  • For plaster or pebble finished pools, ensure that your calcium level is at least 200 ppm.
  • Shock your pool.  I recommend using liquid chlorine to bring your Free Chlorine level up to 40% of your CYA level. 
  • For added protection, I also recommend a quality copper-free algaecide like Polyquat 60:
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  • You can also add a winterizing pill to your pool, but it is not be needed if you follow the steps above:
SeaKlear WinterPill Swimming Pool
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SeaKlear WinterPill Swimming Pool
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Step 4: Lower the water

Next, you want to lower your water level to approximately 4 inches below the return jets.  This will allow you to blow out the lines and ensure your pipes do not contain any water to freeze later. 

You can lower your water using either your pool pump or a drop in sump pump style like this:

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Step 5: Blow out your lines

To prepare for this step you want to remove all of the return eyeballs, usually with vice grips.  You also want to remove your skimmer baskets, and I recommend adding the returns to the basket and storing them someplace safe for the winter. 

The best way to do this is with a shop vac that has a blower setting.  Put the shop vac blower into the skimmer line and run it until no more water is coming from the returns.  If you have multiple skimmers, I recommend hooking the blower up to each one to ensure there is no trapped water to later freeze. 

Step 6: Protect your equipment

Now that your system should not have any water in it, you can focus on your equipment. 

  • Flip the breaker to your equipment to ensure it does not try and come on during the winter.
  • Locate and remove the drain plugs on each piece of equipment.  Note that pumps and some heaters may have more than one plug so make sure you get them all. 
  • Remove your pump strainer basket, this is also a good place to put all of your equipment plugs just like you did with your pool returns.
  • If you have a saltwater pool, it is a good idea to remove your salt water chlorine generator and store it safely until the spring. 
  • In some climates, it may also be advisable to cover your equipment with a tarp over the winter.  Places with extreme winter temperatures may even have separate structures for their pool equipment to stay protected from the winter.

Step 7: Protect your skimmer(s)

Skimmers are especially vulnerable to winter damage and deserve a separate section.  To protect your skimmers, I recommend:

  • Plug the pool returns with a rubber winterizing plug
  • Once the returns are sealed, pour in pool safe antifreeze like this one at the recommended amounts:

No products found.

  • Plug the skimmer with a plug or I recommend a Gizzmo as it will seal your skimmer while protecting from expanding ice:
Gizzmo 9 Inch Swimming Pool
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Gizzmo 9 Inch Swimming Pool
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  • Pour 1/2 to a full gallon of pool antifreeze into the skimmer
  • The Gizzmo provides your skimmer protection against ice, I also like to add cut-up pool noodles to help absorb any additional expansion from the ice.

Step 8: Cover your pool

Once you have all of the equipment, skimmers, and plumbing winterized, it is time to cover your pool for the winter. 

There are a variety of cover types, with different fastener types or even ones secured by water bags.  Find out what is best for your pool and make sure it is securely covered all winter. 

Some covers for larger pools may need extra support in the middle by using a floating air pillow like this one:

Buffalo Blizzard Air Pillow
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Buffalo Blizzard Air Pillow
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Step 7: Winter maintenance

Now that the hard part is done, you can spend the rest of your winter performing minimal maintenance while dreaming of the next swim season:

  • Minimize leaves and other debris on top of the cover by removing them when the weather permits.
  • Some covers recommend a cover pump to pump off excess water.
  • Periodically check your cover to make sure it is secure.

Re-opening the Pool

I recommend opening your pool before the water warms up to 60 degrees so that you can start maintaining your pool and preventing algae from growing once the water warms up. 

You may still get a freeze after you open your pool.  If that happens, make sure your freeze protection is in place to run your pool if the temperature drops.  See the warm season portion of this guide for more details here. 

To re-open your pool do the following:

  • Clean leaves and other debris off of your cover.  Be careful not to let an entire winter’s worth of leaves dump into the pool when you remove the cover.
  • Remove the cover and set it aside to dry before storing.
  • Remove the Gizzmo and other freeze protection from your skimmer.
  • Reinstall all returns, lubricate all equipment plugs, and reinstall each of those. 
  • Add water to the appropriate level and balance all of your chemicals including chlorine and cya as those likely dropped during the winter. 
  • Fill your pump with water to ensure a good prime, then reinstall the pump basket and lid.
  • Flip the breaker to your equipment.
  • Power on your equipment and check to make sure everything is working properly.

What if I have an above-ground pool?

Above-ground pools should follow the same processes as a cold climate pool, except instead of blowing out the pipes, you simply remove, properly dry, and store the lines.  Some filters and pumps may be easily moved inside which would be recommended if possible. 

FAQ – Cold Climates and Pools

What do I do if it is going to freeze before I closed or after I opened?

Simply make sure your pump is running to prevent water from freezing and damaging pipes and equipment. 

Can I just drain the pool for the winter?

No, pools are designed to hold water.  Completely draining could risk severely damaging your pool.    

Can I use my attached spa after my pool is closed?

Not likely. 

The vast majority of integrated pool and spa combos utilize the same equipment so you cannot close one without closing the other.  I recommend a separate portable spa if you live in a climate where you need to close your pool but still want to use the spa.

Wrap Up

I hope this guide provided you with the knowledge to properly care for your pool over winter and ensure that your pool is ready for the next swim season.

For warm season pools, make sure your pool has continuous running water during freezing temperatures to avoid frozen pipes and equipment damage. Additionally make sure you have a plan in place to quickly drain and winterize your equipment in the event of power outages or equipment failure. 

For colder climates, you want to lower the water, drain and winterize all of your pipes and equipment, and finally cover your pool to keep it protected all winter long. 

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