How to Winterize an In-Ground Pool

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.

   • Consult the manufacturer's instructions to determine how long before covering the pool you should add them.
   • Run the pump for several hours after adding all chemicals to ensure proper mixing.

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.
   

   Warning

   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

   • Insert a conical hose connector fitted to a blower or shop vac and blow out the return lines into the pool.
   • 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.
   

   Warning

   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.
   • 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.
   • Bring all equipment inside for storage over the winter.

   Tip

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

9. Cover the Pool

   Opt for safety covers to protect the pool as well as animals and people or a simple winter cover.

   • Raise all in-ground anchors
   • Unfold the pool cover at one end of the pool in a way that will allow the cover to be dragged onto the pool.
   • Drag the cover over the pool until the steps line up with the anchors
   • Using an anchor tool, hook all the cover straps to the anchors

Pool Winterization in Warm vs. Winter Climates

Depending on where the pool is you might not have to winterize your pool and be able to use it year round. Generally, this is most true for southern states where the weather rarely drops close to freezing.

The best way to determine this is to notice if the temperature ever gets close to freezing or below 50 degrees. This includes the temperature at night or during windy days, which can cause surface freezing. Remember, the point of closing a pool is to protect it from freezing. If there is no risk of freezing then the pool can be used year round.

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.