How to Winterize Your Inground Pool in 6 Steps

For most people, a pool in the backyard conjures images of burgers sizzling on the grill, cold ones by the water, and kids splashing and laughing in the shallow end. And while these are just a few of the perks to pool ownership, it’s also a lot of work to keep the dang thing clean.

Nothing worth having ever comes easy.

But the kids love it, and in the dog days of summer, you’re grateful for your investment. So you balance the water and vacuum the liner and skim the leaves and the wayward beetles off the surface to keep it looking nice all year, and come autumn, you winterize.

Winterizing is an important chore that every pool owner must complete before temperatures dip below freezing. If done incorrectly, your pipes and equipment may crack over the winter, costing up to thousands in repairs, or your pool may look more like a science experiment than a backyard oasis when you take the cover off next spring.

While many homeowners leave winterizing to the pros, seasoned pool owners may choose to take on the job themselves. If this is case, we’ve outlined how to winterize an inground pool in the six steps below.

To complete the following steps, you will need:

• Swimming pool test strips or test kit
• pH, alkalinity, and water hardness balancers
• Pool shock and algaecide OR a winterizing pool kit
• Winter plugs
• Gizzmo(s)
• Air compressor or heavy-duty shop vac
• Safety pool cover OR standard pool cover with water tubes

How to Winterize an Inground Pool

1. Test and treat the water

About a week before you’re ready to close your pool, test the water and adjust the pH, alkalinity, and calcium hardness levels accordingly. Once the water is balanced, add shock directly to the skimmer, referring to the packaging for the recommended amount and handling instructions.

If you are using granular chlorine to shock the water, add it 4-7 days prior to allow the chlorine level to drop before covering, as chlorine can harm your pool cover and destroy algaecides. (Non-chlorine shock will not harm either and can be added closer to closing.) When chlorine levels return to normal, add algaecide and let it circulate for at least a day before closing.

Note: Many professionals recommend using a winterizing pool kit, which typically contains algaecide, slow-release borate floaters, and stain and scale treatments in addition to shock. While using a kit is not strictly necessary, some pool owners prefer the all-in-one approach to winterizing.

2. Clean the pool and remove attachments

When you are ready to cover the pool, start by pulling any detachable elements, such as ladders, diving boards, and stairs, out of the water and putting them away. Then, thoroughly clean the pool, removing any debris and algae you see.

To learn how to get rid of pool algae for good, read our blog article on the subject. Remember: The cleaner the pool is when you close it, the better it will look come spring.

3. Lower the water level and clean the filter

If you have a sand or DE filter, lower the water by setting the filter to “Backwash” for about 10-15 minutes, or until the water level is about 6 inches below the skimmer or tile border. The “Backwash” setting runs the chemically treated water back through the filter as it drains, helping to clean the filter.

Note: Depending on the type of filter you have, there are a few different ways to lower the water level in an inground pool.

4. Disconnect fittings and drain the pump and filter system

Once the water level is where you want it, you’ll want to drain all major equipment and disconnect any fittings that may crack in freezing weather.

Start by turning the valve back to the “Filter” setting, shutting down the filter, and opening the filter drain to remove any water. Then, disconnect your pump and filter, drain it of water, dump out any debris that has collected in the pump basket, and remove any drain plugs.

Next, remove the following:

• The filter pressure gauge
• The chlorinator
• Any pump and filter system fittings or unions
• All return jet fittings
• All skimmer baskets

Store all loose equipment in a dry, covered place.

5. Blow out the lines

Blowing out water from your pool’s plumbing is the most critical step when preparing for freezing temperatures. If done incorrectly, the pipes may crack underground, meaning an expensive and invasive fix next pool season.

If you are unsure how to perform some of the following directions, or if you lack the proper machinery—an air compressor or a powerful shop vac and the necessary adaptors—contact a reputable pool company to complete this step correctly and ensure the longevity of your pool’s plumbing.

To blow out pool lines:

1. Make sure the valves are turned so the skimmers (and main drain, if applicable) are open.
2. Hook up the air compressor to your pump by threading the hose into the drain plug opening. (You may need an adaptor for this.)
3. Run the air compressor and look for bubbles coming from the return lines and/or skimmers.
4. Walk around the pool and plug all return lines. No more bubbles should escape after you’ve secured the plugs.
5. Using a Gizzmo, plug the hole in the bottom of the skimmer, where the bubbles are forming. The Gizzmo will absorb any expansion that results from water freezing in your skimmer over the winter, helping protect the plastic from cracking.
6. If you have a main drain, plug the pipe on your end when you notice bubbles coming from the drain, and close the gate valve to create an air lock in the line.
7. If you have a heater, remove the drain plugs and direct air into the unit by closing off all valves except the one to the heater. Run the compressor until no more water leaves the drains, then turn off the compressor and replace the plugs.
8. If you have a slide, auto vac system, or waterfall, you will need to blow out these lines, as well.

Note: Most professionals recommend against adding antifreeze products to your lines, as it can cause a mess come spring, when it is sucked through the filter and deposited into the pool water. If you blow out the lines properly, there will be no water left in the pipes and therefore no need for antifreeze.

6. Cover the pool

Finally, cover your pool to protect it from sunlight, debris, and precipitation. There are several different types of pool covers, including safety/security covers and standard winter covers.

Safety covers attach to the concrete with spring-loaded straps and are better at bearing heavy loads, such as from snow buildup, than standard covers. To install this type of cover, refer to the instructions manual.

To install a standard pool cover, you will need a set of water tubes to secure the cover over the pool. Using a garden hose, fill the tubes about 80 percent of the way to allow for expansion should they freeze, and place them around the perimeter of the pool on top of the cover. The cover itself should rest on the surface of the pool, not “hammock” above the water.

Note: Never use cinder blocks, bricks, or the like to secure your cover, as these materials will damage the lining should they fall in the pool. Water tubes will not harm the lining should an accident occur.

The Bottom Line

When the weather outside is frightful, putting your feet up by the fireside is just as relaxing as kicking back by the water. And knowing your pool will stay clean and intact through the winter makes relaxing all the easier.

Winterizing a pool isn’t a simple task, however. To prepare your pool for freezing weather, you need to:

• Test and balance the water and add winterizing chemicals
• Thoroughly clean your pool and remove all attachments and accessories
• Lower the water level and clean the filter
• Drain the filter, pump, and heater, and remove fittings
• Blow out and plug the return lines, skimmers, main drain, heater, etc.
• Securely attach your winter pool cover

It’s a lot of work, and repairs are expensive if performed incorrectly. Pool owners who are new to the process may want to consider hiring a swimming pool contractor. Best Pick pool service companies come recommended by your neighbors, and they have all the necessary tools and experience to get the job done right, so you can rest easy this winter.

For tips on hiring the best pool company, read our guest article written by Carnahan Landscaping & Pools, a second-year Best Pick operating in Houston, Texas.