How to  winterize your pool?

How to winterize your pool?

Sebastian, self-taught DIY-er, Exeter

Guide written by:

Sebastian, self-taught DIY-er, Exeter

187 guides

Will your pool be completely or partially closed during the winter season? Depending on the region in which you reside, you may want to consider a method of passive or active winterization. That implies administering water treatments, covering the pool with a suitable cover, cleaning the pool and installing frost protection, gizzmos and winter floats. In the following page, you'll find all our tips for carrying out the successful winterization of your pool.    

Important features

  • Winterization period
  • Active or passive winterization
  • Complete pool closing
  • Partial pool closing
  • Mistakes to avoid
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What is swimming pool winterization?

Winterizing a swimming pool is an annual maintenance operation that is designed to preserve the pool and its filtration equipment during the cold season, when the pool is not used.
One approach is to completely close down the pool, clean it thoroughly, slightly reduce the water level, cover the pool with a winter cover and shut down the filtration system. If the goal is for the pool to be partially closed, the filtration is simply slowed down and the pool will need to be meticulously cleaned once it comes time to re-open it in the spring.

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Swimming pool

When should you start winterizing your pool?

The process of winterizing a swimming pool should be put into motion once the pool water drops to around 12° C and stays that temperature consistently. This is just a general guideline, as waiting a bit before starting the process can keep your pool water cleaner, for longer. The temperature of the water being inexorably dependent on the region in which you reside, it is heavily impacted by things like the outside temperature, the amount of sunshine it receives, whether or not it is covered by a pool shelter and if it is heated.

There is therefore no ideal wintering period that can be generally applied. That being said, most of the time, the winterizing period takes place anywhere from the end of September to the end of October, but the only real signal to start is the pool's water temperature.

Passive or active winterization

Passive winterization

Also referred to as complete winterization and overwintering, this approach implies a complete shutdown of the filtration pump and water treatments. The swimming pool is totally closed during the winter season. Passive winterization is most often used in regions in central and northern France.

Active winterization

Active winterization, also known as semi-winterization, consists of keeping the pool's filtration system on, but at a reduced pace, approximately only two hours a day, and regularly verifying the pH. If you want this approach to be successful, you will need to add a winterizing treatment and continue to periodically maintain your pool. Active wintering is primarily employed by residents of southern France.

Complete winterization or semi-winterization: advantages and disadvantages





Active winterization

- Easier to implement

- Pool is quickly reopened

- Pool's water quality isr preserved

- Pool equipment in constant operation (avoids cleaning, flushing, etc.)

- Requires regular surveillance

- Consumes electricity and wears equipment down

- Requires the use of different water treatment

- Requires the purchase of a frost protection box

Complete winterization


Passive winterization

- Requires only periodic maintenance during winter season

- Does not consume electricity

- Takes longer to start

- Takes longer to re-open pool (adding more water, water treatments)

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Swimming pool

Passively winterizing a swimming pool in 8 steps

1. Treat the water and adjust the pH

Add a shock water treatment to your pool and check and adjust its pH: the pool water needs to be clear and of a neutral pH, not too acid or too basic.

2. Clean the pool

The pool liner shoul be thoroughly cleaned. That includes the very bottom, walls, and water line. We would recommend using a pool vacuum, pool brushes or a pool robot. Depending on your pool, it could also imply a pool ladder, coping, skimmers, filters or pumps.

3. Reduce the water level

By reducing the total volume of pool water by about 10%, that volume of water will provide much needed freshness come time to re-open the pool. You can simply drain a bit of the pool using the bottom drain.

4. Shut down the filtration system

The filtration system is powered off, drained, cleaned,dried and stored in a warm, dry place.

5. Add a winterizing treatment to the water

A winterizing treatment is designed to limit the development and formation of limescale on the pool liner. The treatment is directly added to the pool's water, administering a dose that is proportional to the pool's total volume.

6. Block off any holes

The discharge nozzles, the primary drain plug and any brush points are obstructed once they are drained of any standing water.

7. Install gizmos and winterizingng floats

Designed to compensate forthe pressure that frost creates on the skimmer's housing, gizzmos, sometimes spelled gizmos, are placed in the skimmer's basket. Winterizing floats have the same role: to absorb any increase in water pressure when the water expands in volume as it freezes. The gizmos are laid out in the pool diagonally and partially submerged in the pool water.

8. Cover the pool

The pool needs to be covered with a winter cover to prevent any external pollution from contaminating the water (dead leaves, dust, etc.).

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Winter cover

Actively winterizing a swimming pool in 6 steps

1. Add winterizing product to the pool water

Pour a specially designed winterizing treatment into the pool water once its temperature has dropped to low for swimming. Apply the treatment as many times as indicated by the treatment's application instructions.

2. Check the water quality and equipment status

It's important to periodically check the pool water's pH and adjust as required. While you're at it, might as well take a quick look at the skimmer basket and the surface of the water (look out for outdoor pollution).

3. Install a frost protection box

The pool's filtration system is programmed to run about two hours a day but it can also be configured with a frost protection system that triggers the automatic filtration when the pool water reaches a certain temperature.

4. Preventing the pool from freezing

Running the skimmers and the pump creates movement in the water. With this simple action, the pool heats up just enough to avoid freezing over.

5. Cover the pool

Cover the pool to protect the water from impurities (dead leaves, dust, etc.) with a winter cover or a pool net.

6. Monitor equipment

Regularly check the pool's overall status by looking at the general condition of the pool liner, the nozzles, the water surface and the pump. When the time has come to re-open your pool, you will need to clean the pool from top to bottom.

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Clean the pool

6 mistakes to avoid to winterize your pool

1. Emptying the pool completely

This is completely useless and damages the swimming pool. It is a structure that needs to have the constant pressure provided by the water, especially when it comes to the liner, which must to stay solidily attached to the walls.

2. Winterizing the pool too early

You are better of waiting for the water to drop to about 12° C. Water that is warmer than this is still of satisfactoryquality, while anything below this is a breeding ground for bacteria.

3. Not cleaning the pool before winterizing

A pool must be winterized with clean water andequipment, no matter what winterizing approach you end up choosing.

4. Not using winterizing treatments

Failing to realize that your pool water requires a specific treatment when it is unused or less filtered will see you run the risk of having to resort to expensive and cumbersome treatments come springtime or completely replace the entire volume of pool water.

5. Using a bubble cover or no cover at all.

To succesfully winterize your pool it needs to be covered with a winterizing cover. Failing to cover your pool at all is a deliberate choice to let the pool water decline into cloudy and polluted water.

6. Failing to prevent your pool from freezing

Water expands in volume when it freezes and this has very direct, expensive consequences for the whole range of swimming pool devices. Be sure to adequately prepare for the risk of freezing, depending on the winterizing approach you end up choosing.

More information

A pool is designed to enjoy! To get the most of of yours, follow the links below for related accessories, advice from our editors and more helpful guides:

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Guide written by:

Sebastian, self-taught DIY-er, Exeter, 187 guides

Sebastian, self-taught DIY-er, Exeter

Redo a roof with wooden beams? Check.Advise Mister everybody in the DIY shop? Check.Redo the bathroom plumbing? Check.Fit together, build the walls, paint a partition, throw my hammer in a rage thinking that it will fix the problem? Check. The DIY motto ? Learning is better than delegating… well, it's also a question about your wallet! The satisfaction? The beer at the end of the job! What do the best have in common? The influence of Gyro Gearloose, Mac Gyver and Carol Smiley depending on your generation, a good dose of curiosity, a average hand-eye coordination and a taste for risks… and if it doesn't work, try again! Advise you? I'll do my best!

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