Pool season is winding down, leaves are collecting on the bottom, and the water is starting to turn green. With closing day around the corner, it is tempting to pull the cover over the pool and deal with it next spring.
The better approach is to clear the water and correct the balance before closing. A cover helps keep debris and sunlight out, but it will not fix an existing algae problem or unbalanced water.
At Standard Chemicals, we know that good pool care starts with understanding what your water needs. Here is what to do before you put the pool away for winter.
1. Remove Leaves and Brush the Pool
Start by removing leaves, sticks, and other debris from the water and pool floor. Empty the skimmer and pump baskets, then brush the walls, steps, corners, and other areas where algae can collect. Use a brush appropriate for your pool's finish.
Leaves and other organic material consume chlorine as they break down. Removing them gives your treatment less contamination to work through and keeps that debris from sitting in the pool all winter.
2. Test the Water Before Adding More Chemicals
Do not assume the usual weekly tablet routine is enough once the pool starts turning green. Use a reliable test kit to check:
- Free chlorine and total chlorine
- pH
- Total alkalinity
- Calcium hardness
- Cyanuric acid, also called CYA or stabilizer
Correct pH as directed by your shock label before treatment. If you have used stabilized chlorine tablets all summer, pay particular attention to CYA. Excess stabilizer can reduce chlorine's effectiveness, and adding more shock does not remove that stabilizer.
If the water is clear but tinted green, or changed color immediately after a chemical addition, have it checked for metals too. Green water is not always an algae problem.
3. Treat the Algae and Keep the Filter Running
For algae, use a chlorine treatment labeled for that purpose and calculate the dose from your pool volume, test results, and the specific product directions. A routine maintenance dose may not be enough for an established algae bloom.
Calcium hypochlorite shock can raise chlorine without adding CYA. It also adds calcium, so check your calcium hardness when deciding whether it is the right treatment for your pool.
Keep the pump and filter operating through the cleanup as directed. Brush again, vacuum settled debris, and clean or backwash the filter according to its instructions. Retest the water and continue treatment only as the label directs.
Water that changes from green to cloudy still needs attention. Let the filter remove the remaining particles before shutting the system down for winter.
Pro Tip: Start several days before your planned closing. Allow time for treatment, filtration, and retesting instead of expecting one last-minute bag of shock to finish the job.
4. Recheck the Water Balance for Winter
Once the algae is cleared, test again. Cleanup treatments and any replacement water may have changed your readings.
For context, common operating ranges for many plaster pools include:
- pH: 7.2 to 7.6
- Total alkalinity: 80 to 120 ppm
- Calcium hardness: 200 to 400 ppm
Your final winter targets can differ from these operating ranges. The right balance depends on your pool's finish, sanitizer system, cover, and expected water temperature. Colder water can become more aggressive toward plaster, so have the calcium balance checked for winter conditions. Vinyl and fiberglass pools may have different requirements.
Follow the closing instructions for your pool and cover, including the acceptable chlorine level before covering. If using a winter algaecide or closing kit, follow its application sequence and timing. A closing kit does not replace clearing the algae first.
5. Use Water Temperature to Plan Your Closing
An empty swimming schedule does not mean the water is too cold for algae.
As a practical guideline, aim to close when the water stays around 60°F or below, while leaving enough time to winterize before freezing weather. Cooler water slows algae growth, but it does not eliminate the need for treatment.
If your closing appointment arrives while the water is still 66°F, focus on getting it clean and balanced and arrange follow-up water checks while it stays warm. This is especially useful with a mesh cover that allows some sunlight through.
If freezing weather is approaching, have a pool professional protect the plumbing and equipment rather than delaying winterization to keep treating the water.
6. Winterize the Equipment Before Installing the Cover
Once treatment is complete and the water is ready, finish the physical closing. Set the water level, drain or winterize the plumbing and equipment, and remove accessories according to your pool and equipment manufacturers' instructions.
Do not completely drain a permanent pool for a routine winter closing. The correct water level depends on the pool and cover design.
Install a properly fitted pool cover and secure it as instructed. An ordinary tarp is not a safety cover. Solid covers and mesh covers also have different drainage and maintenance requirements, so follow the instructions for the one you use.
7. Check the Pool During the Off-Season
Periodically check the cover, water level, and any accumulated debris or standing water. Follow the cover manufacturer's instructions for removing water and debris.
Arrange water testing during extended warm spells and as spring approaches. If more treatment is needed after the equipment has been winterized, get instructions for safe application and circulation before adding it.
Opening before sustained warm weather returns can also help you address changing water conditions before algae gets a head start.
Pool Shock for Your Pre-Closing Cleanup
Standard Chemicals offers 68% Calcium Hypochlorite Pool Shock in twelve sealed 1 lb pouches for chlorine treatment without adding stabilizer. Check your water first, then choose the product and dose according to the label.
Always follow label directions, wear the specified protective equipment, and never mix pool chemicals together or put cal hypo into a feeder used for another chlorine product.