Pool winterisation:
active or passive?

Why winterise your pool in French-speaking Switzerland?

An outdoor pool used during the warmer months needs to be prepared for winter. When water freezes, it expands: inside a pipe or a piece of equipment, this expansion can cause damage. The pump, filter and parts of the circulation system exposed to cold therefore need particular attention.

The climate in French-speaking Switzerland is not uniform. A garden near Lake Geneva, a property on the Swiss Plateau and a pool at higher altitude do not experience the same conditions. MeteoSwiss notes that ground frost can occur in lowland areas as early as September and is more frequent in some parts of the Jura. A mild day is no guarantee against a cold night.

Winterisation also aims to limit dirt and deposits during the months without swimming. Leaving the water clean and the equipment protected means less cleaning to catch up on when the pool reopens.

When should winterisation begin?

The calendar provides an indication; the water temperature and local forecast guide the decision. Preparation takes place in autumn, followed by winterisation once the water stays consistently cold, before frost threatens the equipment.

Manufacturers generally suggest thresholds of around 12 to 15 °C, depending on the method and products used. Follow the recommendations for your installation rather than applying a single threshold to every pool. In the meantime, continue cleaning and monitoring the water.

Method 01

Active winterisation: keeping the pool running at a reduced level

With active winterisation, filtration remains in operation with a schedule adapted to the temperature and equipment. The water is checked and its treatment adjusted throughout winter. This method is mainly suited to situations with a limited risk of frost and where regular monitoring is possible.

The pool remains visible and restarting it in spring can be simpler. However, filtration continues to consume electricity and the installation cannot be left unattended.

There is no filtration duration that suits every pool. Settings depend in particular on the pump, circulation system and weather. A frost protection device may activate filtration when the temperature drops, but its exact function should be checked in the manual. Water circulation alone does not guarantee protection of the entire installation, particularly during prolonged freezing weather or a power cut.

Method 02

Passive winterisation: shutting down the installation

Passive winterisation means stopping filtration after preparing the pool and protecting the equipment. It is particularly relevant where significant frost is expected or where the owner cannot carry out frequent checks.

Preparation includes cleaning, balancing the water, applying suitable treatment and protecting the relevant components against frost: pipes, pump, filter and additional equipment, according to their manuals. Plugs, skimmer protection, winterising floats and the cover are chosen to suit the pool.

The water level should not be lowered automatically. Some covers or automatic slatted covers require a specific level to work correctly. The manufacturer’s instructions take priority. Passive winterisation does not mean completely emptying the pool.

This method limits the electrical operation of filtration during winter. It still requires careful preparation and checks of the cover and water level. “Switched off” does not mean “forgotten until spring”.

Active or passive: how do you choose?

The choice depends on actual conditions: altitude, exposure, plant room layout, cover and the owner’s availability. In French-speaking Switzerland, a method may suit one property and be unsuitable for another, even in the neighbouring canton.

Four things to prepare before winter

1. Clean the pool. Remove debris, brush the surfaces and maintain filtration components according to their manuals.
2. Check the water. Check the parameters relevant to your treatment. Choose compatible products and follow their instructions.
3. Protect each piece of equipment. Heat pumps, salt chlorinators and accessories may require specific procedures, even if the rest of the pool is still running.
4. Plan regular checks. Check the cover, water level and, with active winterisation, filtration operation during cold spells.

Prepare for winter with Piscines Privées

Unsure whether to choose active or passive winterisation? We can examine your pool’s configuration and guide you towards suitable preparation. Discover ourpool maintenance service in French-speaking Switzerland and ourwater analysis services.

For an initial discussion, send us your municipality, pool type and, if possible, a photo of the plant room on WhatsApp. These details will help us understand your installation.