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How to Close An Inground Pool in 9 Steps

Matt Giovanisci, Founder and CEO of Swim University By Matt Giovanisci | October 8, 2018

Sunshine streams in through your windows, as you climb out of bed. When you step out onto your patio with your morning cup of coffee, you realize it’s pool season again! Your excitement may quickly turn to disgust when you pull back your pool cover and find a swamp where your beautiful pool used to be. At the end of last season, you slapped on a winter cover, and figured you’d sort out the water next year. Big mistake.

Learning how to close a pool doesn’t have to be a huge pain. Plus, it’ll make opening next season a breeze. You’ll need fewer chemicals to make the water swimmable again. You may even extend the life of pool surfaces and accessories by taking preventive measures. It takes a little extra effort, but that’s nothing compared to how much work opening will be if you don’t close your pool the right way.

Why Should You Learn How to Close a Pool?

Maybe you’ve always thought closing only applied to public pools that are closed for the winter. But closing your inground pool is one of the most important parts of maintaining your pool, keeping it swimmable, and saving you money.

Think about it for a minute. While your pool is uncovered all summer, you probably see all kinds of debris end up in the water—leaves, bugs, twigs, and anything else that may blow in. Because you’re maintaining and probably using your pool several days a week, you remove all those things from the water before they have a chance to settle and decay in the water.

Now imagine if you left your pool uncovered all winter, but you weren’t out there every day using, skimming, brushing, and vacuuming it. All that debris—and probably more—is still ending up in your pool. But now it’ll sit there for months, slowly rotting, settling onto the bottom, clogging up the skimmer, and wreaking havoc on your pool’s water chemistry.

When the time to open your pool rolls around again, you’ll have a LOT of work ahead of you to make it swimmable again. You may even have some damage that needs to be repaired. And you’ll need more chemicals to get the water back to its clean, clear, pristine condition.

In other words, it will take more time and more money to set things right again. And all of that could’ve been avoided if you’d just learned how to close your pool before winter hit. Do you really need any other reasons to close it?

When to Close Your Pool

A lot of pool care relies on timing, and when to winterize your pool is as important as how.

If your local temperatures typically stay below 65°F (18°C) during the off season, wait until the temperature falls below that point to close. Lower temperatures are inhospitable to algae and can help the water stay clearer longer. Leaving your pool open until the weather cools means you can easily clean, test, balance, and use your pool right up until it’s time to close.

On the other hand, if your off-season sees several warm days of 65°F (18°C) or more, you can test and balance the water chemistry on those occasional warm days throughout the offseason to help keep your water cleaner until it’s time to open again.

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How to Close Your Pool

Depending on the climate where you live, the winterizing process will vary. Regardless, it’s really all about prevention.

For example, removing water prevents damage that could occur when that water freezes. Balancing the water and putting in a few additives helps prevent complications from poor water chemistry. And using a winter cover protects your water from the elements while a safety cover may help prevent drowning accidents.

If your pool is in Arizona, Florida, or any place that stays relatively warm (but too cool for pool use) during the off season, you won’t need to take freeze prevention measures. Just keep your pool pump hooked up, and run it daily throughout winter.

But if your pool will spend the holidays buried in snow, you’ll need to blow the water out of the pump to prevent ice damage that can happen when even a small amount of water in the pipes freezes and expands.

Take note of the differences in how to close a pool depending on whether your climate is cold or warm during the off season so you can follow the best steps for your pool.

What You’ll Need

The supplies you’ll need to winterize your pool will also vary a bit depending on your climate, what types of pool accessories you have, and whether you’ve been maintaining water chemistry right up until closing day—which makes the closing process much easier.

It’s a long list, huh? Don’t worry. Most of it is stuff you probably have on hand already since you use it to maintain your pool when it’s open.

But making sure you have everything on hand before you start will save you a last-minute trip to the pool store in the middle of the closing process.

1. Clean Your Pool

Before you do anything else, clean your pool. Use a pool brush attached to a telescoping pole to scrub your pool walls and floor, getting into the nooks and crannies as best you can.

This will help kick up any sediment hanging around, as well as disturb the beginnings of any algae spores. Manually vacuum all the stuff you kicked up while brushing.

If you have any symptoms of algae, use an algae brush and be especially thorough. This breaks up the algae so it can be vacuumed up. It also disturbs any blooms so they’re more susceptible to the treatment chemicals you’ll be adding.

2. Test the Water

After vacuuming, you can either test the pool water yourself with a test kit, or take a water sample to your local pool store if you want a super-accurate reading.

It’s important that the levels (pH, alkalinity, etc.) are properly balanced as this will help protect the pool from corrosion and scale build-up that can occur while it’s closed.

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Complete Liquid Test Kit for Pools and Hot Tubs

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Important: Make sure the chlorine level is below five parts per million (ppm). If it’s too high, it may destroy the other additives you put in before they have a chance to work.

3. Add Winterizing Chemicals

Once the chlorine level is where it needs to be, add the other chemicals that will help prepare your pool for winter.

Wondering how to close a pool quickly? You’ve got two choices: use a non-chlorine shock add the other chemicals immediately afterward, and close the pool.

Or, you can simply balance your water, cover the pool, and hope for the best. We don’t recommend this unless you want to uncover a nasty, green pool full of algae and who knows what else the following spring.

You may not need all of these winterizing chemicals, depending on where you live and what kind of water you have.


Add one dose to prevent spore growth throughout the offseason. If your cover has a mesh panel or other way for dirt, leaves, and other debris to enter the water, use a double dose of algaecide.

Our Top Pick
Pool Algaecide 60 (Copper-Free)

A copper-free algaecide to help prevent your pool from turning green.

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Metal Sequestrant

If your water has high levels of metals (if your water comes from a well, for example), add Metal sequestrant when closing. This suspends any metals in the water, so they can’t settle onto your pool surfaces, oxidize, and eventually cause stains.

Pool Metal Remover

Helps prevent staining by removing iron, calcium, manganese, copper and other metals from your pool water. Also helps protect plumbing and pool walls from rust, stain, and scale. Used for all pool openings and closings.

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Pool Enzymes

While you won’t need them for dealing with swimmer-introduced contaminants such as sunscreen, pool enzymes can help take some of the burden off the algaecide by attacking organic contaminants.


Chlorine tablets or floaters may not dissolve or distribute correctly when used for winterizing a pool, especially since the pump will be turned off most of the time, if not during the entire off season.

To avoid the damage that could cause, use products designed to be left in a closed pool, such as a WinterPill. It contains sanitizer and clarifier, but dissolves over several months under the winter cover.

What About Antifreeze?

If you blow out your lines properly, you shouldn’t have to worry about them freezing. But it can sometimes be difficult to get every drop of water out of the lines. Or maybe you’d just rather take a quicker route. Either way, you can use antifreeze.

Choose one rated down to 10°F (-12°C). If your winter temperatures are regularly much colder than that, and you still prefer to use antifreeze, check the temperature rating on the product you choose to be sure it can adequately protect your pool under those harsher conditions

Important: If you choose to use antifreeze, be sure to purchase the one designed for use in pools, not car antifreeze. The type made for pools is non-toxic, unlike the automotive version.

Pool Antifreeze Chart

4. Shock Your Pool

The night before—or even a few days before—closing and putting on the cover, shock your pool one last time. This isn’t a difficult step, but be sure to follow the correct procedure when you to avoid any chemical mishaps and to ensure it does what it’s supposed to.

Add the pool shock per the manufacturer’s instructions. If you saw any beginning algae blooms, add double or triple the amount of shock, depending on the type and severity of the algae problem.

Run the pump overnight to distribute the shock throughout the pool and circulation system. Test your water the following day to make sure it’s balanced.

Important: It’s always best to shock your pool at night when the sun can’t gobble up your chlorine before it has time to work.

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Calcium Hypochlorite Pool Shock (Cal-Hypo Shock)

This fast-acting, quick-dissolving swimming pool shock kills bacteria, controls algae, and destroys organic contaminants in pools.

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5. Lower the Pool’s Water Level

If you live in a warm, dry climate, you can skip to the next step.

The reason for removing some water at the end of the season is to prevent freeze damage and, to a lesser degree, overflow. Ideally, your water level should be below the tile border, or the bottom edge of the skimmer if you don’t have a tile line, or whichever is lower, if you have both. If you have thaws or a rainy winter, it’s a good idea to check the water level while the pool is closed.

The exact level to drain the water down to is determined by which type of cover you’ll be using, and the type of pool surface you have. The water helps support your cover, and the weight of any snow or debris that ends up on top, so it’s important to follow the manufacturer’s recommendations too.

Vinyl Liner

Bring the water to one inch below your skimmer opening or tile line, whichever is lower.

Plaster or Non-Vinyl Pool Liner

If you’re using a solid cover, lower the water to six inches below the skimmer or tile line. When using a mesh cover (or none, but you really want to use a cover), lower the water to 18 to 24 inches below the skimmer or tiles. If you have an automatic pool cover, be sure the water is no lower than the bottom of the skimmer.

How to Lower the Water Level

Lowering your pool’s water level is as simple as pumping to waste until the water line is where you want it to be. Because you’ll have just added chemicals, be vigilant about directing wastewater appropriately.

Usually, you’ll drain pool water into the nearest city sanitary sewage, but some places have different rules for residents. Be sure to check the laws in your area by contacting the local water or environmental quality department. Your city code enforcement office may also be able to point you in the right direction regarding local pool wastewater regulations.

6. Backwash and Clean the Filter and Pump

The last thing you want to do is leave a bunch of nasty debris and bacteria sitting in your filter all winter. Yuck. Get all that gunk out before you close so you start the next pool season with a nice, clean filter.

Cartridge Filter

Remove it, wash it with pool filter cleaner or muriatic acid, then rinse it and allow it to dry thoroughly before you store it.

Sand Filter

Use a cleaner made for sand filters, or backwash it thoroughly. Be sure to flip the valve back to filter after backwashing. Drain all water out of the pump, filter, and pool heater, if you have one. Toss the plugs into your skimmer basket for storage.

Diatomaceous Earth (D.E.) Filter

You can use a cleaner made for D.E. filters, or you can backwash the same way you’d backwash a sand filter.

7. Blow Out the Lines

If you live in a warmer climate where the temperature doesn’t get to freezing or below, and you want to avoid blowing out your lines, you can use antifreeze. Or you can skip to the next step.

First, don’t panic. This won’t require any lung power on your part. Unless that’s some kind of weird challenge you feel you must take on.

If you live in a cold climate and opt to blow out the lines, you must remove every last bit of water from the lines, pump, and filter. This will prevent fractures caused by ice in the lines and equipment. Blowing out the lines means you won’t need to add antifreeze, either.

Your pool plumbing is not built to withstand excess pressure, so purging the lines of water is a delicate process. Because it involves blasting air through the plumbing, you could inadvertently do serious damage. Blow out the lines only if you’re confident you know what you’re doing.

Note: We highly recommend hiring a pool pro for this step if you’re anything less than absolutely certain of your ability to do it yourself. Screw this part up, and you could be in for thousands of dollars in repairs.

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Air Compressor Kit with Hose and Fittings

This is the ideal air compressor we recommend for blowing out the lines in your inground pool when closing/winterizing.

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07/16/2024 01:08 am GMT
  1. Remove all the return fittings and skimmer baskets.
  2. Remove all the drain plugs from your filter system.
  3. Set the multiport valve to recirculate.
  4. Set the valve in front of your pump to the skimmer line.
  5. Attach your air compressor or ShopVac to the pump’s drain plug opening. You may need an adapter.
  6. Blow air through the system, watching for bubbles from the return lines and skimmer.
  7. Use your Shop-Vac to remove the water being blown out of the skimmer until it’s dry.
  8. Insert a rubber plug or Gizzmo in the hole in the bottom of the skimmer.
  9. Install rubber plugs in each return line as you see air bubbles escape from them. If you live somewhere cold, you may need to use straight pressure plugs in the return lines.
  10. Turn the valve in front of your pump to the main drain setting to move air in that direction.
  11. Watch for bubbles from the main drain in the deep end. Let it run for about a minute.
  12. Turn the pump valve back to the skimmer line, then shut off your air compressor.
  13. Put a plug inside the pump in case the valve leaks.

What About Salt Water Pools?

You’ll still need to blow out your lines. But you’ll also need to remove your salt water chlorinator, drain it, and store it. Flip the circuit breaker and make sure power and gas to the heater are off. Then store any controllers, robotic cleaners, and other electronics indoors for the winter.

8. Remove Any Pool Accessories

Leaving things installed around your pool like ladders and rails can cause three problems.

The prolonged exposure to chemicals during winter can damage the finishes on items like this. They may even rust, which means the rust will get into your pool, which means you have another problem to deal with when you open.

Also, when you cover your pool, you want it completely covered. Unless you know a master custom pool cover maker who can create one that fits securely, even around ladders and rails, removing them will allow the cover to fit properly and protect your pool better.

Finally, if your pool is not securely and completely covered, it leaves room for debris, but more importantly, small animals and possibly even children to fall into the pool. Removing accessories ensures the pool is completely covered, and can help prevent tragic accidents.

Once you’ve removed your accessories, clean and dry them thoroughly, then store them in a clean, dry place. Keep them out of direct sunlight to minimize potential weather damage.

Also be sure to remove the fittings from the return lines, including the line for your automatic cleaner, if you have one. Then pull out and clean your skimmer baskets. You can toss the fittings into the clean skimmer basket to help you keep track of them.

9. Install a Winter Cover

You have a couple choices for covering your pool in the off season. The weather in your region and your budget will probably determine which type you go with.

Regular Winter Cover

This will protect your pool from contaminants and keep all the chemistry work you’ve done nicely under wraps. Use water tubes or pool cover weights to keep it from sinking into your pool over time. They’ll also prevent any gaps along the edges of your pool. The cover manufacturer’s instructions may suggest how many tubes to use, so read them carefully.

Be sure you have a pool cover pump to remove pooling water from the cover, both to protect the cover and any people or animals who could become trapped or drown in that pooled water.

Protect your pool cover by keeping it clean, but don’t use anything sharp like a shovel or rake. A regular push broom works well to remove leaves and even a few inches of snow at a time. You can also use a rubber broom with a squeegee to help remove water. Even though you don’t need to clean your pool daily when it’s closed, it’s good to check on the cover regularly.

Pool Safety Cover

A more expensive option than standard covers, a pool safety cover can help protect your pool from the elements while also keeping people and animals from falling into the water.

They’re often solid, but are also available in mesh as well as hybrid versions that have a mesh panel to let water drain into the pool. If you use a mesh or hybrid safety cover, you may need to lower the pool water level again during the winter if it rains or snow melts into the pool.

Here’s a list of the best recommended inground pool winter covers.

Don’t Be Afraid to Hire a Pro

Even though it’s pretty easy to winterize a pool, especially if you’re a seasoned do-it-yourselfer, some parts aren’t so straightforward. Blowing out the lines can be tough to do correctly, and is especially vital if you live somewhere with freezing winters.

Regardless of whether you handle every other aspect of pool care on your own, closing your pool for winter may be the one time of year you hire a pro. That’s totally okay! When you make sure your inground pool is closed properly, you’ll prevent freeze damage that can cost a fortune to repair, and re-opening your pool in the spring will be a breeze.

Happy Closing!

Here Are 3 Ways to Get More Pool Maintenance Help

  1. Download our FREE Pool Care Cheat Sheet: It’s a free, easy-to-use guide to help you keep track of taking care of your pool.
  2. The Pool Care Course: You’ll get 30+ step-by-step videos and a downloadable guide with everything you need to know about pool maintenance.
  3. The Pool Care Handbook: It's an illustrated guide to DIY pool care, including water chemistry, maintenance, troubleshooting, and more.
Matt Giovanisci, Founder and CEO of Swim University
Matt Giovanisci is the founder of Swim University® and has been in the pool and spa industry since 1993. Since then, his mission is to make pool and hot tub care easy for everyone. And each year, he continues to help more people with water chemistry, cleaning, and troubleshooting.
Save Time and Money with Our FREE Pool Care Cheat Sheet
Keep your pool clean and balanced every week. You won't have to worry about your pool anymore. This simple cheat sheet is all you need. And it's free!

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