Opening the Pool After Winter – correct steps, mistake-free

With the first sunny days of spring, every pool owner's thoughts drift to relaxing by the pool. However, before the first swim, rigorous technical preparation is necessary. Opening the pool after winter is not just an aesthetic formality, but an important technical process for protecting equipment and ensuring water safety.

A correct start to the new season will save you money in the long run, preventing costly problems such as liner degradation, pump failures, or excessive chemical consumption to recover compromised water. This guide is structured to help you go through each stage logically and efficiently, whether you own an inground or an above-ground pool.

In short: Opening the pool after winter involves choosing the right time, checking equipment, cleaning the basin, starting filtration, and treating the water in the correct order. If you follow these steps, the water becomes clear quickly, and you avoid problems all season long.

1. When is the right time to open the pool after winter?

One of the most common mistakes is delaying the pool opening until the weather becomes scorching hot. Many owners wait for June, but the optimal moment is dictated by water temperature, not air temperature.

It is recommended to start the pool opening procedure (commissioning) when the water temperature consistently reaches 12°C - 15°C.

1.1. Why not wait longer?

• Algae explosion: Above 15°C, microorganisms and algae begin to develop rapidly. If the winter cover allows light to pass through or if the water has warmed up under it, you will find a green "swamp" that is hard to recover. The cost of chemicals to treat green water is often double the cost of energy to run the pump for a few hours a day as a preventive measure.
• Pollen and debris: Spring brings large amounts of pollen. If the pool is functional, the filtration system (skimmers) will capture these impurities before they sink and stain the liner or grout joints.
• Technical check: If you discover a pump failure or a pipe leak, it is much better to repair it in April, when technicians are more available, than in the middle of the season when waiting times are long.

In Romania's climate, this moment usually coincides with late March or April. Even if you don't swim immediately, an active pool with clear, recirculated water is a superb decorative element in the yard and is ready anytime for the first heatwave.

2. Important checks before opening the pool

Before removing the cover, make sure you have all the necessary logistics at hand. Nothing is more frustrating than stopping halfway through the process because you are missing a gasket or a substance.

2.1. Chemical Inventory

Even if you have products left from last year, check the expiration date. Liquid chlorine loses concentration over time, and pH testers (liquid reagents) often expire from one season to another.

• For Shock: Granular chlorine (rapid chlorine) or liquid.
• For Balancing: pH Minus corrector (most frequently needed) or pH Plus.
• For Prevention: Concentrated Algaecide.
• Optional: Flocculant (attention: only for sand/glass filters, never for cartridge filters!).

2.2. Cleaning Accessories Inventory

Check the condition of the leaf net (make sure the mesh isn't torn), the wall brush, and the floating hose. If you use an automatic robot, check the condition of its filters.

3. How to prepare the equipment and technical room?

This is the stage where the "engineer" in you needs to pay attention to details. A careful visual check can save you from floods in the technical room.

3.1. Visual check of pump and filter

Winter and frost can be silent enemies. Check the pump body and pre-filter for any fine cracks caused by water not being drained correctly. Also, inspect the 6-way valve (for sand filters) or the cartridge filter housing.

• Check manometer: If it's stuck or broken, replace it. It's the only instrument that tells you what's happening inside the filter.
• Check sand/glass: If you haven't changed the filter media for 4-5 years, now is the ideal time, before filling the installation with water. If the filter body is cracked, you might need a new filter.

3.2. Reassembling accessories and dismantled parts

All drain plugs removed in autumn (from pump, filter, heat exchanger, heat pump) must be put back in place.

• Very Important: Grease the gaskets (O-rings) of the plugs with silicone grease before threading. This prevents "pinching" the gasket and ensures a perfect seal without overtightening.
• If you dismantled the ladder, diving board, or shower, mount them on the deck now. Check mounting screws for oxidation (even stainless steel can oxidize superficially).

4. Correct steps for opening the pool (Execution Order)

Respecting this logical order saves you double work. Do not treat the water before physically cleaning the basin and do not start filtration without checking the water level.

4.1. Removing and cleaning the winter cover

If you used a winter cover, it is likely full of leaves, dust, and rainwater.

• High Caution: Try not to spill the dirt from the cover into the pool water. Use a small submersible pump to evacuate water accumulated on top of the cover.
• Remove leaves with a leaf net or a soft broom.
• After removing the cover, wash it on a clean surface (on grass or concrete), let it dry completely, and store it in a place protected from rodents.

4.2. Cleaning the basin and topping up water level

Now you will see the real state of the water. Do not panic if it is slightly cloudy.

• Use the deep net to remove any vegetable debris (leaves, branches) fallen to the bottom of the basin. These consume chlorine and hinder treatment.
• Very Important: Top up the water level to the middle of the skimmer. During winter, the water level drops (or was intentionally lowered). The recirculation pump must not be started if the water level is below the skimmer intake, as it will draw air and can lose prime or burn out.

4.3. Starting the filtration system (Priming and Backwash)

Before switching the valve to the "Filtration" position, you need to revived the filter media (sand).

1. Priming: Fill the pump pre-filter with water, put the lid on, and open the valves on suction (Skimmer, Main Drain, or Vacuum).
2. Backwash: Move the 6-way valve to the "Backwash" position (always with the pump off!). Start the pump and let it run for 1-2 minutes, until the water coming out of the sight glass is clear.
3. Rinse: Stop pump, move to "Rinse", start pump for 30 seconds. This resettles the sand.
4. Filtration: Stop pump, move to "Filtration" and start the system. Now water circulates normally.

Check for leaks at pump unions or filter lid.

4.4. Initial Chemical Treatment (Shock and Balancing)

Chemicals are added only in this strict order:

1. pH Adjustment: This is the critical step. Measure the water pH. It will likely be unbalanced. Add pH Minus or pH Plus to bring it into the 7.2 - 7.6 range.
2. Shock Treatment: After pH is stabilized (wait 2-4 hours with filtration on), apply the shock chlorine treatment (rapid chlorine). Dosage is usually 15-20g / cubic meter of water (check product label). Dissolve granules in a bucket of water before pouring into the pool, around the edges.
3. Algaecide: The day after shock, add the shock dose of algaecide to prevent algae growth.

4.5. Monitoring and final adjustment

Leave the filtration system running continuously (24h/24h) for 2-3 days until the water becomes crystal clear. Check filter pressure and do a Backwash whenever pressure increases by 0.5 bar above normal.

5. Specific differences: Inground vs. Above-ground Pools (Intex/Bestway)

Although chemical principles are the same, equipment dictates important procedural differences.

5.1. Particularities for starting inground pools (Concrete/Liner/Fiberglass)

Inground pools often have technical rooms below water level.

• Watch out for floods: Before opening any valve, check if there is infiltrated water in the technical room. A flooded pump is a major electrocution risk.
• Main Drain: If you winterized the pool actively (without draining below nozzles), gradually open the main drain valve to help recirculation, but monitor pressure.

5.2. Procedure for above-ground pools (Intex, Bestway)

These pools are often equipped with cartridge filtration systems or smaller sand pumps.

• Cartridge Filters: Do not reuse an old cartridge from last year, even if you washed it. Start the season with a new cartridge; the cost is negligible compared to the benefit of correct filtration.
• Major Prohibition: NEVER use flocculant (clarifying agent) if you have a cartridge filter! Flocculant irreversibly clogs the cartridge pores in minutes. Use only "Clarifier" type products (specially marked for cartridge filters).
• Hose Check: Flexible hoses on this type of pool become brittle from the sun. Check for cracks at hose clamps.

6. Common problems at opening and practical solutions

Even if you followed the steps, unforeseen situations can arise. Here is how to solve them like a pro.

6.1. Water is green or cloudy – What to do?

• Green Water: Indicates presence of live algae. Solution is Chlorine Shock + Algaecide. Make sure to check pH first (if pH is high, chlorine doesn't work). Leave pump running continuously.
• Cloudy Water (milky): Indicates fine particles in suspension or high hardness (limescale).
  1. Check pH.
  2. If you have sand filter: Use a flocculation agent (liquid or "flocculant cartridges" in skimmer). Stop pump overnight to let impurities settle to bottom, then vacuum them in the morning directly to waste (WASTE valve position), not through filter.
  3. If you have cartridge filter: Use only clarifier and wash cartridge very often (2-3 times a day).

6.2. Pump not priming or abnormal pressure

• Not drawing water: Check if pool water level is high enough (middle of skimmer). Check if pre-filter basket is full of water and lid is tight (air leaks are enemy no. 1).
• Pressure too high: Filter is dirty – do a Backwash.
• Pressure too low: Pump basket is clogged with leaves or pump impeller is blocked.

7. Common mistakes to avoid at season start

Avoid these rookie errors that can cost dearly:

7.1. Completely draining the pool

Never drain a pool (especially inground ones with liner) without consulting a specialist. Ground pressure can collapse walls or lift the pool bottom if the water table is high (buoyancy phenomenon).

7.2. Throwing chlorine granules directly into the basin

Chlorine granules that reach the pool bottom undissolved will irreversibly bleach the liner, leaving white spots. Always dissolve granules in a bucket of water.

7.3. Performing shock chlorine in full sun

UV rays destroy unstabilized chlorine in a few hours. Always perform shock treatment in the evening, after sunset, to allow it to act all night.

7.4. Ignoring water hardness

If supply water is very hard (full of limescale), walls will become rough. Use a limescale sequestrant at first filling.

8. FAQ about opening the pool

9. When it's worth calling a professional pool opening service

Although pool opening can be done DIY, there are situations when specialized team expertise is safer and more economical:

• You were away for a long time: If the pool wasn't checked all winter and water is black or smells bad.
• Faulty equipment: If you notice pump leaks, strange noises, or automation panel errors you can't diagnose.
• Lack of time: The complete cleaning and balancing process can take a few days. A professional team has powerful pumps and industrial vacuums that reduce intervention time to a few hours.

For a worry-free opening, you can always request an offer for our Pool Maintenance and Repairs service.

Conclusion

Opening the pool after winter does not have to be a chore. With a little planning and by following the correct order of steps, you will ensure that your equipment has a long life and that your family enjoys safe, crystal-clear water. If you run into major difficulties, do not hesitate to call on our service team for a professional intervention.