How to Winterize an In-Ground Pool

A closed in-ground swimming pool with a cover on top
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Project Overview
  • Working Time: 1 - 3 hrs
  • Total Time: 4 days - 1 wk
  • Yield: Winterized in-ground pool
  • Skill Level: Intermediate
  • Estimated Cost: $25 to $100

In areas with colder weather, pools have to be closed in the winter. Water is removed from the lines and pool equipment to prevent freezing. During this time, the pump doesn't run, which prevents the water from properly circulating. If not properly winterized, pools can become a haven for algae, bacteria, calcification, and other problems.

Whether you've hired this process out in the past, this is your first season with a pool, or you're simply looking for ways to streamline the process and guarantee you get the job done right, we've laid out the steps for you. Properly winterizing your in-ground pool is a crucial step in maintaining it and ensuring it lasts for years to come.

When to Winterize an In-Ground Pool

Believe it or not, it is possible to winterize your pool too early. While it may seem like a negligible difference, it's important to wait until the temperatures in your area consistently stay below 60 to 65°F. This will lower the likeliness of your pool being overtaken by algae, which thrives in warmer temperatures.

However, waiting too late to winterize your pool risks damaging your pool equipment due to freezing temperatures.

Before You Begin

This guide is not one size fits all and should be adjusted for your specific pool and region. Always refer to and follow any local guidelines or regulations or instructions from the manufacturer(s) of your pool equipment.

What You'll Need

Equipment / Tools

  • Conical hose connector
  • Blower or shop vac
  • Standard pool cleaning tools
  • Submersible pump or siphon
  • Air pillow (optional)


  • Pool winterization kit
  • Return line plugs
  • Skimmer plug
  • Pool antifreeze (optional)


Follow these steps to winterize most in-ground pools, adjusting them as needed to fit your specific pool and equipment.

  1. Remove and Store Accessories

    Before getting started, remove any pool accessories that aren't necessary for winterizing the pool. This includes ladders, cleaners, baskets, floats, and any other nonessential pool accessory.

    Wash them off, let them dry, and store them in a safe place until time to reopen the pool.

  2. Thoroughly Clean Pool and Filter

    Using a net, pool vacuum, and brush, thoroughly clean and remove all debris from the pool.

  3. Test and Balance Water Chemistry

    Test the water chemistry against the following parameters:

    • Alkalinity: 80 to 150 ppm
    • pH: 7.2 to 7.6
    • Hardness: 175 to 275 ppm

    Test and balance in the order listed. If the measurements you achieve are slightly higher than the parameters presented, it's likely okay, given that the pool will not be used during the off-season and the levels will decrease over time.

  4. Add Shock and Algaecide

    To prevent algae and bacteria growth, add pool shock and algaecide to the pool. These products vary, so consult the manufacturer's instructions to determine how long before covering the pool you should add them. Additionally, some products shouldn't be used at the same time, such as algaecide and chlorine shock. After adding each product, run the pump for several hours to circulate them.

  5. Partially Drain Pool

    Using a submersible pump or siphon, partially drain the pool until the water sits 1-2 inches below the skimmer and pool lines.


    Refrain from draining your pool more than is absolutely necessary. This will allow excess weight to accumulate in your pool cover as well as remove the weight of the water, which protects the pool from the freezing and shifting of the ground.

  6. Blow out Lines

    Starting with the return lines at the pump, insert a conical hose connector fitted to a blower or shop vac and blow out the return lines into the pool. Once the water quantity is no longer substantial, plug all of the lines using a threaded plug or rubber expansion plug.

    Repeat this process with the skimmer and skimmer line, then insert a skimmer plug to prevent water from entering the line during the winter.

  7. Fill Lines With Pool Antifreeze (Optional)

    To ensure your pool lines are fully protected from a freeze, you can go one step further and fill them with pool antifreeze according to the manufacturer's instructions.


    Pool antifreeze is specially designed for this application. Never use standard antifreeze to protect pool lines.

  8. Clean and Drain Water From All Equipment

    Clean all pool equipment thoroughly. To prevent freeze damage, remove the plugs from all pumps, filters, heaters, and other equipment and drain any remaining water. Place the plugs in the pump basket for safekeeping. If possible, place any equipment inside for storage over the winter.


    If your pool has a sand filter, set the filter to "winterize" before removing the lower drain plug.

  9. Cover the Pool

    Using the pool cover of your choice, cover the pool. Opt for safety covers to protect the pool as well as animals and people or a simple winter cover. To prevent damage to your pool cover due to sagging, an air pillow can be placed between the water and cover before covering.

Pool Winterization Tips

The main thing to remember when winterizing your pool is to not rush the process. Make sure the chemicals have time to do their job and that you've thoroughly removed all water from lines and equipment. Failing to properly shock and treat the water for algae can lead to bacteria and algae taking over your pool, while improperly balanced chemicals will cause hardening and calcification on the pool's surface. Getting this job done properly is the best way to protect your investment.

When to Call a Professional

It's important to winterize your pool the right way. While this guide is a great starting point for most pools, all pools are different and so is the equipment that runs them. Modify the instructions given to your specific pool and equipment, and if you're unconfident in the necessary processes, it may be wise to reach out to a professional who can offer guidance and set you up for future success.