How to Winterize a Pool

By Malea Ritz | Advertiser Disclosure

For pool owners, having a pool can feel like an added luxury during the summer. Having a place to cool off and host guests are great benefits, but pools are an investment that require lots of care. When summer comes to an end, there are steps you should take to ensure your pool will live on to its former glory in the next season. 

If you’re lucky enough to live somewhere with mild winters, you may not have to close your swimming pool at all. During the summer, any insects or debris that fall in your pool’s water are easily resolvable with a skimmer. 

However, if you live somewhere cold, fishing out these items isn’t as easy or appealing between snowflakes and frost. In this case, winterizing your swimming pool and closing it for the season will help avoid maintenance headaches and financial burdens down the road and keep your pool area safe.

Steps to winterize a pool

Follow this step-by-step guide to winterizing your pool for the winter months.

1. Obtain the necessary tools

Before you begin the process of winterizing your pool, it’s a good idea to grab any items you’ll need to complete the job.

Time to complete the job: Winterizing your pool should take only a day or two. Begin a week before you plan to close it.


  • Winter chemical kit/winterizing chemicals
  • pH water testing kit/test strips
  • Clarifying enzyme supplement
  • Above-ground pool winter cover
  • Cover winch and cable
  • Cover clips
  • Pool air pillow
  • Swimming pool antifreeze
  • Pool cover pump
  • Pool vacuum
  • Pool brush
  • Pool skimmer
  • Algaecide
  • Pool antifreeze
  • Shock
  • Pool cover/safety cover

2. Remove pool items and debris

To reduce the hassle on yourself when opening the pool next season, remove any ladders, rails, pool floats, or toys; use a pool vacuum to clean the bottom and sides of the pool; remove drain plugs; brush down the walls; and skim the surface with a pool skimmer. This will prevent any remaining debris from settling at the bottom of your pool over the winter.

3. Test the water

Just like the tests you or a pool professional perform on your water during the pool season, testing your water before closing it will help keep it in prime condition for years to come. Do this about one week before closing your pool. You can purchase a water testing kit and use test strips to test the water yourself or you can gather a water sample to bring to a local pool store to be tested.

If you’re testing the water yourself, the ideal pH is between 7.4 and 7.6 and the total alkalinity should be between 100 and 150 parts per million (ppm). Calcium hardness should be between 175 and 225 ppm and chloride should be between one and three ppm.

Keep in mind: Having these numbers on the high side is a good thing, as the levels will decrease throughout the winter.

4. Add in winterizing chemicals

There are different chemicals and methods to use for an in-ground swimming pool vs. an above-ground pool, but the goals are the same—to keep the water clean. Balanced water is less likely to damage your pool liner, so it’s worth investing in a winter chemical kit. Determine if your kit requires you to run the pool filter while adding chemicals to your pool and read the instructions before you start.

Winterizing an above-ground pool

If you have a pool heater or use well water, use a kit that includes a metal control. Avoid using algaecide and chlorine shock simultaneously, as chlorine can prevent algaecide from working by breaking it down. 

1. Alter the alkalinity

Alkalinity is the amount of alkaline substances, like carbonates, bicarbonates, hydroxides, found in your pool and is pH’s counterpart to balancing water. To increase alkalinity levels, add a base, such as an alkalinity increaser or sodium bicarbonate. To decrease the alkalinity, add muriatic acid.

2. Perfect the pH

pH is a measure of how acidic or basic the water is in your pool. If the level is low, the water is more acidic, and if the level is high, the water is more basic. If your water is basic, use a pH increaser to balance it out. If the water is acidic, add a base or pH decreaser to level it out.

3. Focus on calcium hardness

Calcium hardness measures how soft or hard your pool water is. If hard water deposits calcium in your pool or plumbing, it can form a crusty substance and build up over time, blocking your pool filter and pump. If the water in your pool is too soft, it can take calcium from inside the pool and damage tiles or corrode metal.

Test your water with a liquid test kit. If the water hardness level is above 400 ppm, you’ll need to lower it, and if it’s below 200 ppm, you’ll need to raise it.

For soft water, add calcium chloride or a calcium hardness increaser. For hard water, use a flocculant to attract excess calcium in your pool. After using the flocculant, clean the walls and floor of your pool to remove excess calcium.

If you have a concrete or plaster pool, calcium levels between 200 and 275 parts per million is the sweet spot. 

4. Shock your pool

Add shock to your pool to revitalize the pool’s sanitizer before the winter. There are two options for shock chemicals: fast-dissolving and regular calcium hypochlorite. With a typical shock, the process can take between eight to 24 hours, so add this pool cleaner the night before closing so that it has time to be effective.

5. Add in winter algaecide

If you’d like to avoid a green, murky pool, add in some winter algaecide and a clarifying enzyme treatment to further stunt algae growth. Follow the instructions on the package to determine the correct amount you should add to your pool.

Winterizing an in-ground pool

Before winterizing your in-ground pool, here are a few materials you’ll need:

  • Algaecide—Add a dose of algaecide to prevent spores from growing. If your cover is made of mesh where some debris may be able to enter the water, add a double dose.
  • Metal sequestrant—If your water comes from a well, it may be high in metals. Add metal sequestrant to prevent any metals in the water from settling, oxidizing, and staining.
  • Pool enzymes—These enzymes can help alleviate the work of the algaecide to remove contaminants. 
  • WinterPill—Opt for products that are designed to be left in the pool, as the usual chlorine tablets or floaters may not dissolve completely in the winter because of the lack of help from the pump. WinterPill has a sanitizer and clarifier and will dissolve over the course of several months under the pool cover.
  • Antifreeze—If you worry about getting every drop of water out of your lines, choose a pool antifreeze (make sure you purchase one specifically designed for pools, not cars) rated down to 10°F (-12°C). If your winter temperatures are much lower, check the temperature rating on the antifreeze and ensure it will work under those freezing temperatures.

1. Lower the pool water

If the weather is mild in the winter where you live, you can skip this step. If you live in a colder climate, removing some pool water will prevent freeze damage and overflow. Note: you’ll know how much water needs to be removed depending on the pool liner you have.

  • Vinyl liner—The water level should be one inch below the tile border or bottom edge of the skimmer, depending on whichever is lower.
  • Plaster or non-vinyl pool liner—The water should be six inches below the skimmer or tile line.
  • Mesh cover—Drain your pool, so that the water level is 18 to 24 inches below the cover.
  • Automatic pool cover—Make sure the water is no lower than the bottom of the skimmer.

2. Clean the pool filter

The filter is an essential aspect of pool cleanliness—no one wants to swim in a mucky pool or lift the pool cover to find dirty water next season. If you have a cartridge filler, use a filter cleaner to soak the cartridge. For sand or DE filters, backwash your filter. Then, remove any leftover debris and build-up in the filter tank.

3. Hire a professional to blow out the pool lines

In a mild climate, pool antifreeze may do the trick here. Otherwise, every bit of water needs to be removed from the lines, pump, and filter. Purging the lines is a fragile process, so hire a professional to avoid doing serious damage to your pool.

How to winterize a saltwater pool

In the case of saltwater pools, the first step you should take is to clean and vacuum the pool. Once that’s complete, follow these steps:

  1. Check and adjust pH and alkalinity levels. You should also check the salt levels at this time with a saltwater pool test kit.
  2. Use a winter chemical kit to treat your pool water and prevent algae from growing during the winter.
  3. Lower the water levels.
  4. Remove the salt water chlorinator, drain it, and store it.
  5. Test the circuit breaker to ensure power and gas to the heater are turned off.
  6. Store any ladders, robotic cleaners, controllers, and electronics indoors for the winter.
  7. Add a cover to your pool.

Additional tips to consider to ensure your pool is ready for winter

Keep these additional tips in mind as you winterize your pool:

Use a pool air pillow

An air pillow is designed to protect your above-ground pool from freezing water, rain, snow, and ice, as it compensates for the pressure of wintry precipitation on the top of your cover. Inflate the air pillow to 50% or 60% of its capacity and position it in the middle of the pool.

Install a winter cover

For an above-ground pool, place a winter cover over the pool and secure it with a cable and winch or cover clips and a cable. For in-ground swimming pools, use water tubes or pool cover weights to keep the pool cover from slipping. Consider investing in a pool cover pump to keep the pump dry all winter.

Winterize any water features

When winterizing your pool, don’t forget to address the waterfall, steps, and rails. Make sure the waterfall feature is turned off, vacuum the pool steps, and remove any rails, ladders, and diving boards from the area. This will extend the lifespan of these features and prevent them from freezing.

Hire a professional when necessary

It’s OK to ask for help when winterizing your pool, especially if you’re feeling overwhelmed or are confused on how to complete a task. Call your local pool store and schedule a time for a pool professional to come out and winterize your pool. Doing so will help ensure the pool stays in great condition for years to come. 

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