Winterize your pool

to winterize your pool in active or passive mode, follow Ondilo's advice

Winterizing your pool protects it and its equipment from freezing. If you're among those who think it's enough to drain your pool in winter and refill it in spring, you should know that this is a big mistake to avoid! The ground around your pool will exert pressure on the structure. As a result, your pool may crack or warp if left empty for long periods. Last but not least, proper winterization will make the next season much easier. As you can see, winterizing is an essential step for all pool owners. There are two ways to do this: active winterizing or winterizing. We explain everything in this article!

When to winterize your pool?

You need to winterize your pool when the water temperature reaches 12°C (including at night!). Depending on the region you live in and the weather, this is usually between late September and mid-October. It's important to winterize early, because frost is your enemy. It can cause serious damage to structures and pipes alike. You've been warned!

This is a relatively time-consuming stage, as it involves thoroughly cleaning your pool and storing the equipment for the winter in the right conditions. Allow a full day's work, or a weekend if you opt for passive winterization.

How to choose between passive and active wintering?

  • Passive winterization is recommended if winters are rigorous in your location (temperature below 5°C, frequent freezing). This procedure allows the protection of the pipes from freezing. This includes the total stop of the treatments and the filtration during the whole winter period.
  • Active winterizing is for mild winters (temperatures above 0°C). Dynamic winterization involves idling your pool, without draining the water. All you need to do is keep your filtration system running at idle speed (1 to 3 hours a day). Secondly, to regularly treat your water quality, not forgetting to clean the filters when necessary.

Steps for passive winterization

Here are the steps for successful passive wintering:

this graphic describes the steps involved in passively winterizing your pool.

Cleaning the pool : Remove debris, leaves and any unwanted residue to avoid potential problems during the winter season.

Add shock treatment products : These products provide effective protection against algae and bacteria.

Start filtration for 24 hours : This allows the chemicals to be evenly distributed in the water, ensuring uniform protection and maximum effectiveness.

Cleaning the filters : Clean filters ensure optimum filtration and reduce the risk of malfunctions.

Lower the water level : The right water level protects the pool structure over winter.

Drain the filtration circuit, close the valves and stop filtration : These actions are crucial to preventing frost damage.

Storing equipment : To protect them from the elements and extend their life.

Pour the wintering product : To protect water and equipment during the winter season.

Add floats : To prevent ice from exerting pressure on the walls of the pool, minimising the risk of structural damage.

Covering the pool : Provides complete protection for your pool against the elements and debris during the winter.

Active wintering stages

Follow the step-by-step diagram to find out how to actively winterize your pool

Cleaning the pool : Remove debris, leaves and any unwanted elements to ensure a clean, healthy base.

Adjust the pH and TAC (Total Alkalimetric Titration) : A balanced pH and adequate TAC are essential for healthy water over winter.

Add shock treatment products : To reinforce protection against algae, bacteria and other contaminants. This stage prepares your pool effectively for the winter period.

Start filtration for 24 hours : This ensures even product distribution and maximum effectiveness in preventing water problems.

Cleaning the filters : Clean filters optimise filtration performance and maintain water clarity.

Pour the wintering product : For greater protection of water and equipment during the winter season.

Filtration adapted to water temperature : To ensure optimum energy use while maintaining healthy water.

It is not compulsory to cover your pool during active wintering. Therefore, we recommend that you only cover your pool if temperatures drop unusually low, or in the event of wind or heavy rain, which can affect water quality.


Your pool is now winterized and ready for the next season! Would you like more information? Discover our article 5 mistakes to avoid when winterizing your pool. If you are using a connected sensor, read our tips for winterizing your ICO.

In winter, we strongly advise you to protect your ICO connected sensor when winterizing your pool.