How To: Close a Pool for the Winter

Closing your pool properly protects your investment from cold-weather damage, and will spare you a litany of maintenance headaches come next year.

By Savannah Sher and Michael Franco | Updated Oct 25, 2021 11:09 AM

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how to close a pool

Of all homeowner responsibilities, few so clearly indicate the end of summer as closing the swimming pool. Properly done, pool closing ensures that when you head back outdoors next summer, you will not have to complete a battery of maintenance tasks before splashing in for your first dip.

Winterizing a pool also performs the important role of protecting your equipment from damage caused by freezing. Knowing the steps and what chemicals you put in the pool for winter can help. Here’s an overview of how to close a pool for winter the right way.

Before getting started, make sure you have the required tools and supplies for closing your pool for the season.

Closing a Pool for the Winter: 10 Steps to Getting the Job Done

While many might opt to have professionals close their pools for winter, it’s a task that’s totally doable with the right tools, equipment, and know-how. Follow these 10 steps to ensure your pool is well protected during the off-season.

STEP 1: Clear the pool of debris and pool scum.

Before closing up your pool, it’s important to ensure it’s as clean as possible to prevent the growth of bacteria. A clean pool also avoids clogging of the filtration system after the pool has been closed. Follow the steps you typically would follow when cleaning your pool, taking extra care to diligently remove dirt and grime.

Vacuum and brush the pool carefully to remove dirt from the sides and bottom. Scrub the sides if mold or grime has built up. Remember also to remove any debris with a handheld skimmer. At this time, clean out the skimmer basket.

STEP 2: Test and balance the pool water.

You’ve done it all summer long, and now you must test and balance the chemicals in your swimming pool once more. Ensure the water is well balanced before closing your pool for the season. First, test the water’s pH level and alkalinity as well as calcium hardness using a pool test kit.

Next, use the water treatments at your disposal to get the pH between 7.2 and 7.6, the alkalinity between 80 and 120 parts per million (ppm), and the calcium hardness between 180 and 200 ppm.

how to close a pool

STEP 3: Add winterizing pool additives and chemicals.

Along with balancing the water levels as you do during the summer, some chemicals can be added to keep your pool water clean and clear all winter long. These beneficial chemicals ensure that the pool doesn’t develop scale or bacteria while it’s closed.

About a week before you plan to stop using the pool, put in a phosphate remover (if you own a pool, you already know phosphates promote algae growth). Stain and scale chemicals prevent the buildup of metals and mineral buildup in the water.

STEP 4: Shock and chlorinate your pool.

Even if your water is clear, introduce a superchlorinating powder, known as pool shock. The product should contain at least 65 percent sodium hypochlorite. For use, consult the directions listed on the packaging of the shock you buy.

Typically, a 1-pound bag is enough for 10,000 gallons of water. Mix the product with some pool water in a large bucket. Then, as the filter is running, pour the mixture into the pool.

Wait until the total chlorine level returns to a range between 1 and 3 ppm. This will probably take a few days. Next, add an algaecide as a further measure to keep those tiny, green pool-tinters at bay through the cold months. Again, choose a product designed for pool closings. The amount to use varies by pool volume; follow the instructions provided by the algaecide manufacturer.

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A pool closing kit includes all the chemicals you might need to stabilize the water chemistry of your pool. Buying the kit might cost less than buying everything separately. Shop around online or check prices at your local pool supply store.

STEP 5: Lower the pool’s water level.

If the water in your pool is in danger of freezing based on your location, it’s important to lower the water level before closing your pool for the season. If you live in a warm climate where temperatures rarely dip below freezing, this step might not be necessary.

The precise water level depends on your pool’s cover. Those with mesh covers should ensure the water level is 12 to 18 inches below the skimmer, while those with solid covers should aim for a water level that’s 3 to 6 inches below the tile.  For an in-ground pool, run your filter or use a siphon pump to bring the water level down.

For an above-ground pool, lowering water levels isn’t necessary. Simply remove the outlet hose from the skimmer basket.

STEP 6: Clean and backwash the pool’s filter and pump.

If you have a sand filter, backwash it to discourage algae growth in the filter element. If you have a removable filter, take it out and clean it thoroughly.

To backwash a filter, start by turning off the pool’s heater. Turn off the filter, then choose the ​​multiport filter valve setting that’s labeled as “backwash” or “drain to waste.” Some filtration systems are already connected to a waste collection receptacle, while others require that you connect a backwash hose that is directed to a waste-disposal site.

Turn on the filter and run it for between 3 and 5 minutes, until the water runs clear. Turn the ​​multiport filter valve to the rinse setting and run it for 30 seconds before turning off the filtration system.

how to close a pool

STEP 7: Clear the pool pump’s lines.

Because residual water can freeze inside your pool equipment and water lines and cause them to expand and crack, they must be as dry as possible to avoid wintertime damage. It might be necessary to blow out the lines with an air compressor. Should doing so prove impossible (or deeply inconvenient), you can head off ice-related problems with a swimming pool antifreeze.

The draining process is easier for above-ground pools: Take off all the hoses and remove the plug from the bottom of the filter. Owners of above-ground pools are advised to make use of a pool pillow. Placed in the center of the pool and tied to its sides, these air-filled rings help prevent water in the pool basin from freezing.

For in-ground pools, this precaution is only recommended if you live in an area with especially harsh winters.

STEP 8: Remove all pool accessories.

Next, remove all accessories—like ladders and diving boards—from the pool. This is a necessary step to ensure the winter pool cover fits correctly. This is also the time to remove skimmer baskets and other wall fittings from the pool.

Before putting them away for the winter, clean all accessories thoroughly and leave them out to dry on a clean surface. Store ladders, diving boards, and other peripherals in a clean, dry place during the off season.

STEP 9: Install a winter pool cover.

A well-fitting winter pool cover is essential for keeping your pool clean and clear while it’s not in use. There are two types of winter covers typically found on the market: mesh and solid vinyl. Mesh covers are more affordable and don’t require any maintenance over the winter but they can allow debris to get into the pool’s water.

Solid covers require a pump to remove rainwater and melted snow from the top. Be sure to continue precautions such as locking the gates of pool fences to avoid having a small child or pet drown in water collecting on the cover before it drains. A solid cover that remains in place should keep the pool water below clear.

how to close a pool

STEP 10: Monitor your pool’s chemical composition on a monthly basis.

Over the winter, it’s still important to consistently adjust and monitor your pool’s chemical balance. The best practice is to check the chemical composition monthly during the off-season and add chemicals as needed to sustain desirable levels.

Try to maintain a pH of around 7.4 to prevent corrosion and scale from building up. Ensure the water is chlorinated at a level of 2 to 4 ppm to kill bacteria. Aim for alkalinity in the standard 80 to 120 ppm range. Look for a minimum calcium hardness of 200 ppm to protect the surface of the pool from staining.

FAQs About How to Winterize a Pool

Though you now know more about how to close a pool, you might still have some lingering questions. The following are answers to some of the most common questions about how to close down your pool for the winter and how to maintain it during cold weather.

Q. Should I run my pool pump in freezing weather?

When temperatures dip below freezing, it’s important to run your pool pump continuously to keep the water moving. This should happen automatically if you have a freeze guard.

Q. How do you put antifreeze in pool lines?

After draining the water to winter levels, put antifreeze in the skimmer opening to prevent water from freezing in the pool’s plumbing lines. Most pools require approximately 1 gallon of antifreeze to ensure the plumbing is protected.

Q. When should you open your above-ground pool?

Deciding when to close or open your pool depends on weather and pool type. Close an above-ground pool when daytime temperatures are consistently above 70 degrees Fahrenheit. While it might still be a bit chilly to swim at 70 degrees, there are a number of benefits to opening your pool earlier in the season, including preventing algae from reproducing.

Q. Can you over-shock a pool?

Yes, it’s possible to over-shock a pool. Pool “shock” is simply a concentrated version of chlorine, and using too much of it can result in your pool water becoming cloudy. If you over-shock your pool, avoid swimming in it until the water clears up. Remove the cover—if you have one—to speed up the process.

Final Thoughts

While you can hire professionals to close your pool for you, you’ll save money by doing it yourself. By following these 10 steps, you’ll ensure that your pool is protected and well maintained for the off-season. Hopefully, you now feel equipped with the necessary information to close your pool this fall so that it’s ready to go next spring.

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