Many swimming pools spend the winter without a cover or protective tarpaulin. Whether this is because they are located in areas with a temperate climate, because they are used all year round, or simply because they do not have a cover, it is possible to keep the water in good condition by following specific maintenance guidelines.
In this guide, we explain how to maintain a swimming pool in winter without covering it, what care it needs, which products to use and how to avoid problems such as algae, green water or limescale build-up during the colder months.
Can you keep a pool uncovered in winter?
Yes. It is entirely possible to maintain an uncovered swimming pool in winter if you carry out regular maintenance and adapt the treatment to the season.
As it does not have a cover, the swimming pool is more exposed to leaves, dust, rain, insects and other debris. Furthermore, sunlight can encourage the growth of algae, even during the winter in certain areas.
The key is to maintain the water balance and not to leave the pool completely until spring.
Advantages and disadvantages of not covering the swimming pool in winter
Advantages | Disadvantages |
The swimming pool is ready for use, weather permitting. | More dirt builds up on the surface. |
This avoids having to put the tarpaulin up and take it down every season. | Greater exposure to leaves, dust and insects. |
It allows for continuous visual monitoring of the water’s condition. | It may require more filtration hours than an indoor swimming pool. |
In areas with mild winters, maintenance is usually straightforward provided that water parameters are kept under control.
How to maintain a swimming pool in winter without covering it – step by step
1. Clean the swimming pool before starting winter maintenance
Before scaling back your regular maintenance routine, carry out a thorough clean:
- Remove leaves and debris with the leaf rake.
- Vacuum the bottom of the swimming pool.
- Scrub the walls, steps and waterline.
- Clean the skimmers and the pump’s pre-filter.
A clean swimming pool will require less chemical during the winter.
2. Adjusts the water balance
The chemical balance remains essential even when the swimming pool is not in use.
Parameter | Recommended value |
pH | 7,2 – 7,6 |
Alkalinity | 80 – 120 ppm |
Free chlorine | 1 – 2 ppm |
Checking these levels once a month helps to prevent cloudy water, limescale build-up and disinfection problems.
3. Use a winterising treatment
Even if the swimming pool remains uncovered, it is advisable to apply a winterising product to help:
- Prevent the growth of algae.
- Keep the water clear.
- Reduce limescale and metal deposits.
- To facilitate water recovery in spring.
It is advisable to use the dose specified by the manufacturer when the water temperature falls below 15 °C.
4. Keep the treatment plant running
One of the most common questions is whether the treatment plant needs to be switched off in winter.
The answer is no. Filtration is still necessary, although for a shorter period than in summer.
Water temperature | Indicative filtration |
Over 15 °C | 4–6 hours a day. |
Between 10 and 15 °C | 2–4 hours a day. |
Less than 10 °C | 1–2 hours a day, depending on the weather. |
If a lot of leaves or dirt end up in the pool, it may be necessary to increase the filtration time slightly.
5. Remove dirt regularly
As there is no tarpaulin, more rubbish will accumulate on the surface.
It is recommended that:
- Run the leaf rake over the garden every few days.
- Empty the skimmer baskets.
- Remove any twigs, leaves or insects before they sink.
The less organic matter there is in the water, the lower the risk of algae growth.
What products does an outdoor swimming pool need during the winter?
During the winter, you don’t need to use all your summer products, but you do need to use some basic treatments.
Product | What is it for? |
Prevents algae and limescale build-up during the winter months. | |
It maintains the chemical balance of the water. | |
Disinfectant (chlorine, active oxygen…) | It keeps the disinfected water fresh throughout the winter. |
Maintenance algaecide (if necessary) | It helps prevent the growth of algae in swimming pools that are heavily exposed to the sun. |
How often should an uncovered swimming pool be checked in winter?
An outdoor swimming pool needs a quick check-up roughly every 3 or 4 weeks.
Monthly maintenance checklist
- Check the pH.
- Check the level of disinfectant.
- Remove leaves and dirt.
- Check the water level after heavy rain.
- Clean the skimmers and pre-filter.
- Check that the treatment plant is working properly.
These are quick tasks that help to avoid more intensive treatments in the spring.
The most common problems when maintaining an uncovered swimming pool in winter
Green water
It usually occurs due to a lack of disinfectant or a build-up of organic matter.
How to prevent this: continue with the winterising treatment and check the chlorine levels regularly.
Algal bloom
It can even occur in winter if the temperatures are mild and there are plenty of hours of sunshine.
How to prevent it: keep the water balanced and filter it regularly.
Murky water following rainfall
Rain washes away dust and organic matter.
What to do: filter for a few more hours and check the pH.
Limescale deposits
They are common in areas with hard water.
Prevention: maintain the chemical balance and use specific maintenance products.
Mistakes to avoid
- Shut down the treatment plant completely for several months.
- Do not check the water until spring.
- Leave the leaves that have accumulated at the bottom.
- Add products without first checking the pH.
- To think that the cold completely eliminates algae.
A little maintenance over the winter prevents most of these problems.
What should you do when spring arrives?
If you have left your swimming pool uncovered over the winter:
- Clean the surface and the bottom.
- Adjusts pH and alkalinity.
- Carry out an intensive treatment if necessary.
- Leave the water to filter for several hours.
- Check that the bath water is ready.
The process will be much quicker than restoring a swimming pool that has been left unmaintained for months.
