Opening a pool is, in fact, the reverse process of closing it for the season: instead of protecting the pool so it can withstand months without use, the goal is to bring it back to a state where the water is safe to swim in again. The order of the steps matters, doing them in the wrong order is often the reason the water takes longer than expected to clear up.
Opening the pool, step by step
Remove the cover
Restore the level
Check pump and filter
Let the water circulate
Rebalance parameters
Wait if the water is green
1. Remove the thermal cover carefully
Before removing it completely, sweep or vacuum the water and debris built up on top so it doesn't fall into the pool as you take it off. Clean it and let it dry thoroughly before storing it, a cover that's stored damp often gets damaged or grows mould between seasons.
2. Restore the water level
It's normal for the level to have dropped over winter due to evaporation. Fill with a hose up to halfway on the skimmer, the level the filtration system needs to work correctly without sucking in air.
3. Check the pump and filter before turning them on
Don't switch on the filtration system without first checking everything's in order:
- Check that the pump's prefilter seals and lid aren't dried out or cracked from the cold.
- Check the pressure on the filter's gauge: if it reads higher than usual, it probably needs a backwash before starting up.
- If it's a sand filter, consider whether it's time to replace the sand, more than 5-6 years of use is usually a good time to check it.
4. Let the water circulate before swimming
Run the filtration system continuously for 24-48 hours before the first swim. Water usually comes out of winter somewhat cloudy, and continuous filtration is what brings back its clarity, trying to swim the same day almost never turns out well.
5. Rebalance the water parameters, in this order
The order here matters: adjust pH and alkalinity first, and only add chlorine afterwards. Chlorine added to unbalanced water loses much of its disinfecting effectiveness, so it's wasted money and product. You can check the reference ranges in our complete water parameters guide.
6. If the water is green or very cloudy, don't worry
This is the most common situation when a pool wasn't fully winterised. The solution is almost always the same: shock chlorination, followed by continuous filtration, solves the problem within 24-48 hours in the vast majority of cases. We explain this in more detail in our guide on chemical water treatment.
Frequently asked questions about opening for the season
How long does it take for the water to clear up after winter?
With continuous filtration, 24 to 72 hours is typical, depending on how green or cloudy it was at the start.
Do you need to drain the pool to open it?
Almost never. A full drain is usually only necessary if there's a structural problem or the water hasn't been renewed for several years, in most cases, restoring the level and treating the existing water is enough.
When is the best time to open the pool?
About 2-3 weeks before you plan to start swimming, to give the water time to fully stabilise without rushing.