If you own a swimming pool and live in an area that experiences freezing temperatures, it’s essential to winterize your pool properly. Winterizing—or closing—your pool helps protect it from damage caused by ice expansion, debris accumulation, and chemical imbalances during the off-season. While the process may seem daunting, breaking it down into manageable steps makes it more approachable and efficient.
This step-by-step guide is designed to walk you through the entire process of winterizing your pool, whether it’s above-ground or in-ground, made of vinyl, concrete (gunite), or fiberglass. You’ll learn how to maintain water chemistry, drain equipment safely, store accessories, and cover your pool for long-term protection.
Why Winterizing Your Pool Matters
Before diving into the steps, it’s important to understand the importance of winterizing your pool. Proper winterization:
- Prevents cracking or warping of pool surfaces due to freezing water
- Reduces the risk of algae growth and stains during the dormant season
- Protects pool equipment like pumps, filters, and heaters from damage
- Saves time and money during spring opening by maintaining cleaner water and reducing clean-up work
When to Winterize Your Pool
Timing is crucial when it comes to winterizing your pool. The best time to begin the process is when evening temperatures regularly drop below 65°F (18°C), and you’ve stopped regular usage. Do not wait until the first frost to start winterizing, as cold temperatures can already begin affecting your pool’s infrastructure.
Step 1: Clean Your Pool Thoroughly
Start with a clean pool. A dirty pool at the start of winter will only lead to staining, algae blooms, and higher maintenance come spring.
Brush the Walls and Floor
Use a pool brush appropriate for your pool surface—nylon for vinyl pools and stainless steel for concrete—to scrub all surfaces. This will help dislodge any algae or debris clinging to the walls and floor.
Vacuum the Pool
Manually vacuum or use an automatic pool cleaner to remove all debris and dirt from the bottom of your pool. Be thorough, especially near corners or under ladders where dirt accumulates.
Skim the Surface
Use a skimmer net to remove leaves, bugs, and other floating debris from the surface before you begin chemical treatment or filtration. This helps prevent contamination and unnecessary chemical consumption.
Step 2: Test and Balance Pool Water
Good water chemistry is crucial for protecting your pool surfaces and equipment. Before winterizing, you must test and balance the water to inhibit algae growth and prevent scale formation.
Test the Water
Use a reliable pool test kit or strips to measure the following levels:
- pH (ideal range: 7.2–7.6)
- Alkalinity (80–120 ppm)
- Calcium hardness (200–400 ppm for vinyl liners, 250–350 ppm for concrete pools)
- Chlorine (1–3 ppm)
Adjust and Balance as Needed
Use chemicals such as muriatic acid, sodium bicarbonate, or calcium chloride to adjust the levels. Maintaining balanced water will prevent corrosion or scaling over the winter months.
Step 3: Shock the Pool
Shocking the pool with a high dose of chlorine or a non-chlorine shock kills bacteria, algae spores, and other contaminants in the water. This is an essential step in keeping the water clean.
Types of Pool Shock
| Shocking Agent | Pros | Cons |
|---|---|---|
| Calcium Hypochlorite | Strong oxidation, effective at killing algae and bacteria | Can raise calcium levels in the pool |
| Sodium Dichlor | Stabilized, safe for most pools, effective chlorine boost | Can accumulate in pool water over time |
| Potassium Monopersulfate (Non-Chlorine) | Safe for closing, no chlorine odor or waiting period | Less effective at killing some algae and bacteria |
Apply the Shock
After shocking the pool, run your pump for several hours to ensure even distribution. Always wear gloves and goggles when handling pool chemicals for safety.
Step 4: Add a Winterizing Pool Algaecide
Algae can persist even in cold water, especially if your water wasn’t perfectly balanced. To prevent algae from taking hold over winter, use a premium-quality algaecide specifically formulated for seasonal closure.
Choose a copper-based or quat-based algaecide. Read labels to ensure compatibility with your pool surface and winter cover.
Step 5: Use a Pool Winterizing Kit
To simplify the winterization process, consider using a pool winterizing kit, which contains all the necessary chemicals in the correct proportions for a standard pool size. These often include winter algaecide, stain and scale preventers, and shock.
Step 6: Lower the Water Level
The next critical step is lowering the water level to prepare for freezing conditions:
How Low Should You Go?
- In-ground pools: Lower water to 6–12 inches below the skimmer.
- Above-ground pools: Lower it to about 1–2 inches below the skimmer or as recommended by the manufacturer.
This prevents water from freezing in the skimmer and damaging the equipment or pool structure.
How to Drain the Pool
- Turn off your pool pump and filter system.
- Attach a submersible pump or use the drain plug, if available, to begin draining water.
- Discharge water away from the pool area and your home’s foundation.
CAUTION: Do not lower the water level too much. In in-ground pools, water pressure from the ground could cause the pool to float out of the ground (hydrostatic uplift).
Step 7: Blow Out Pool Lines and Equipment
Draining standing water out of your plumbing lines and equipment is crucial to prevent frozen, cracked pipes. You’ll need a blower or air compressor for this task.
Turn Off Water Flow
Shut off valves leading from the pool to the equipment. Remove the pump’s lid and filter drain plugs to allow air to escape.
Blow Out Skimmer Lines
Connect the air compressor or blower to the skimmer hole. Insert a nozzle or fitting made for this purpose. Blow air through the line to push out any remaining water.
Blow Out Return Lines
These are the jets that return filtered water to the pool. The best method is to blow the water back to the pool or through the main drain, depending on your system. Use a return line fitting for the blower.
Check All Lines
Ensure all lines (skimmer, main drain, return lines, and light conduit) are fully cleared of water. This step prevents freezing and potential damage to your plumbing system.
Step 8: Add Winterizing Chemicals to the Pool
Before installing the cover, add final winterizing chemicals to ensure clean and balanced water throughout the winter.
Winterizing Tablets or Blocks
These slow-dissolving chlorine tablets help maintain chlorine levels over the winter. Place them in your skimmer or a floating dispenser if you’re not removing the skimmer lid.
Dosage Guidelines
As a guideline, use 1 tablet per 5,000 gallons of water. Always follow the manufacturer’s instructions for safe and effective results.
Step 9: Install Winter Pool Plug (For In-Ground Pools)
If you have an in-ground pool and your main drain skimmer lacks a safety plug, install a fitting winter plug in the skimmer. This prevents water from backing up into the skimmer and freezing during winter.
Step 10: Drain and Store Equipment
Properly draining and storing your pool pump, filter, and heater helps avoid damage caused by frozen water inside the equipment.
Pump and Filter
- Turn off the power and unscrew the pump’s lid.
- Drain all water from the pump by removing the drain cap.
- Store the cartridge filter or clean and dry the DE grids.
- Store equipment in a cool, dry indoor location to protect from freezing and moisture damage.
Heater (If Applicable)
If you have a pool heater, drain all water from the heat exchanger. If it’s a heat pump, simply switch it off and cover it outdoors or move it to storage.
Step 11: Install the Pool Cover
The final physical step in winterizing your pool is to install a strong winter pool cover. This helps keep debris out, reduces evaporation, and prevents accidental drownings, especially important if you have pets or small children.
Choosing the Right Cover
- Solid covers (vinyl): Best for keeping debris and water out.
- Mesh covers: Allow rainwater through but still keep debris out.
Solid covers are popular in regions with heavy fall rains or long winters due to better protection against algae and stain-causing organic matter.
Securing the Cover
- Place the cover over the pool evenly.
- Use cover clips or water bags to secure the edges.
- Ensure it’s tight and doesn’t sag excessively in the center to avoid water accumulation.
Some pool covers include a built-in leaf net system, while others require the use of a cover pump to remove rainwater that collects in the center.
Step 12: Monitor Pool Conditions Through the Winter
While the pool is closed, it’s still a good idea to check on it periodically:
- Remove heavy snow or leaves that accumulate on the cover
- Ensure cover tension is maintained through seasonal temperature changes
- Use a cover pump to drain excess rainwater or snow-melt
Optional: Install a Safety Cover for Extra Protection
In addition to decorative winter covers, safety covers have a much tighter fit with a support system that prevents water ponding and keeps people and animals away from the open water.
Safety Covers vs Winter Covers
| Feature | Safety Cover | Winter Cover |
|---|---|---|
| Material Quality | Heavy-duty polypropylene | Thicker vinyl or polyester mesh |
| Function | Pet and child protection, durability, tight fit | General winter protection, debris control |
| Installation | Cable and anchor system | Over the pool and secured with water bags or clips |
| Price | High | Moderate to high |
Final Tips for Winterized Pool Maintenance
While most seasonal pool owners close their pools in the fall, understanding what you can—and can’t—leave to chance during the winter will ensure a smooth spring opening. Here’s a quick checklist:
- Balance water chemistry before closing
- Install a high-quality, secure cover
- Ensure all plumbing lines are properly blown out
- Store pool equipment indoors where possible
- Conduct periodic winter checks to maintain cover integrity
Prepare Your Pool for Winter Like a Pro
Winterizing your pool is an investment in the long-term health of your equipment and pool surfaces. While it may take several hours to complete, the process pays dividends when you open your pool in spring with minimal hassle and expense.
Follow this comprehensive guide, tailor the steps to your specific pool type, climate, and local conditions, and enjoy the peace of mind that comes with knowing your pool is ready for cold weather. If you’re ever unsure about a step or the chemicals you need to use, consult with a local pool professional or your pool supply store for tailored advice and product recommendations.
Why is it important to winterize a pool?
Winterizing a pool is essential to protect it from damage caused by freezing temperatures, debris accumulation, and water chemistry imbalances during the off-season. When water freezes, it expands, which can cause cracks in the pool structure, plumbing lines, and equipment. Proper winterization ensures that your pool remains in good condition and saves you time, money, and effort when reopening it in the spring.
Additionally, winterizing helps prevent algae growth and keeps your pool cleaner throughout the colder months. A well-winterized pool requires minimal maintenance while dormant and allows for a smoother, faster opening process when warm weather returns. For pool owners in regions with harsh winters, taking the time to winterize properly is a crucial step in extending the lifespan of their pool and equipment.
When is the best time to start winterizing a pool?
The best time to begin winterizing a pool is when the water temperature consistently drops below 65°F (about 18°C), typically in late fall. This timing helps prevent algae and bacteria growth, which can still occur in warmer water even if swimming has stopped. Starting the process early enough ensures the pool is completely closed before freezing temperatures arrive.
Weather patterns can vary depending on your location, so it’s important to monitor local forecasts and start the winterization process accordingly. For example, pool owners in northern climates may need to start earlier than those in milder regions. Scheduling your winterization during a dry period can also help ensure proper chemical balance and prevent rainwater from diluting the pool water before it’s covered.
Should I drain my pool completely when winterizing?
In most cases, you should not drain your pool completely during winterization. Leaving water in the pool helps protect the pool structure from external pressure caused by ground movement or water accumulation beneath the pool. Completely draining a pool can also lead to serious damage, especially for vinyl or fiberglass pools, which may warp or become dislodged.
For concrete (gunite) pools, some water should be lowered depending on the type of cover used—below the skimmer for solid covers or just below the tile line for mesh covers. The goal is to leave enough water to stabilize the pool while allowing room for ice to form without causing damage. Always consult your pool manufacturer or a professional to determine the correct water level for your specific pool type.
Do I need to clean the pool before winterizing it?
Yes, thoroughly cleaning the pool before winterizing is a critical step. This includes skimming debris from the surface, brushing the walls and floor, and vacuuming to remove dirt and contaminants. A clean pool ensures that chemicals can work more effectively to keep algae and bacteria at bay over the winter months.
Additionally, you should clean or backwash the filter system to remove built-up particles and optimize its performance during the closing process. Taking the time to properly clean your pool before closing it can significantly reduce the chance of staining, discoloration, and water imbalance issues. In the long run, this simple step contributes greatly to a successful and hassle-free reopening.
What kind of winter cover should I use for my pool?
The best winter cover for your pool depends on your climate, local weather conditions, and pool type. Solid vinyl covers are ideal for areas with heavy precipitation, as they prevent water, leaves, and debris from entering the pool. Mesh covers, on the other hand, allow water to pass through and are suitable for regions with less snow and rainfall.
It’s crucial to invest in a durable, high-quality cover that fits your pool properly and is secured with water bags or a cable and winch system. A properly installed cover keeps the pool safe, clean, and minimizes damage from ice expansion. Choosing the right cover ensures that your pool remains well-protected throughout the winter and makes the reopening easier and less labor-intensive.
How do I balance the pool water before winterizing?
Balancing your pool water before winterizing is an essential step to prevent staining, scaling, and corrosion. Begin by testing the water using a reliable test kit or strips, and adjust the pH to between 7.2 and 7.6. Total alkalinity should be between 80 and 120 ppm, and calcium hardness between 180 and 270 ppm for vinyl pools or 200 and 400 ppm for concrete pools.
Once the balance is correct, add a winterizing chemical kit that typically includes algaecide and a closing chemical blend. This helps ensure the water remains clear and clean throughout the winter by preventing algae growth and metal staining. Proper water balance and winterizing chemicals are crucial for protecting your pool surfaces and equipment, making the spring opening much smoother and less costly.
Can I use regular chlorine to winterize my pool?
You should not rely on regular chlorine alone when winterizing a pool. Instead, use a winterizing chemical kit that includes a strong dose of algaecide, a chlorine shock, and often a stain and scale preventative. These products work together to ensure that the water remains clean, clear, and protected during the long period when the pool isn’t circulating.
While chlorine is important to kill bacteria and algae, winterizing involves lowering the chlorine level to a specific point before covering the pool to avoid chemical degradation over time. After shocking the pool, you should allow the chlorine level to drop to approximately 1.0 ppm before covering. This final balance helps protect the pool water through the winter without causing bleach-based damage to the liner or equipment once circulation stops.