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10 Steps to Winterize Your Inground Pool

When the long summer days come to a close, it's time to think about how and when to winterize your inground pool. Some people don't need to winterize their pool — we're looking at you, sunbelt region! — but if you live in a colder climate, it's a good idea to let your pool hibernate.

As with everything pool related, there is a specific process for winterizing your pool. It's an easy process to follow.

How to Winterize Your Inground Pool

Winter pool closing steps must be done in a very specific order to ensure an easy pool opening the following spring. Follow the guidelines below to close your own swimming pool this winter!

1. Remove Ladders and Accessories

Loosen the ladder anchor socket bolt. When it rises about 1/2 inch, knock it down with a heavy wrench. Wiggle the ladder loose so the pool cover will fit properly. Inspect your ladder treads closely for cracks, and tighten any loose ladder bolts. Most ladders can be stored outside, but plastic steps may do better if stored inside. Also remove any handrails, fill spouts, eyeball fittings, pool cleaners and skimmer baskets. Store in a safe place where you can easily find them again in the spring.

2. Balance Water Chemistry

balance water chemistry before you winterize your pool

It's important to start winterizing with balanced pool water chemistry. Test and balance the water chemistry, and adjust any chemicals if necessary. Balance water chemistry a few days before closing your pool to allow the chemicals time to disperse. Adhere to the following ranges for balancing water chemicals:

  • pH: 7.4–7.6 ppm
  • Total Alkalinity: 80–120 ppm
  • Calcium Hardness: 200–400 ppm
  • Chlorine: 2.0–4.0 ppm

Brush and shock your pool to remove any algae or other organic materials before closing your pool.

3. Clean the Pool

Skim, vacuum, and brush the pool thoroughly, in that order. The pool should be spotless when you cover it. Remove every bit of organic matter possible, and give the pool one final skim (if necessary) before covering it for the winter. The cleaner the pool is when you close it, the better it will look next spring. Any debris or algae left in the pool during closing will dilute the strength of the winterizing pool chemicals.

4. Lower the Water Level

lower the water level to winterize your pool

Lower the water level of your inground pool between 6-12" below the bottom of the tiles, if you have a pool safety cover. For solid covers, only lower the water a few inches below the skimmer. Never lower the water level more than 18", doing so can increase stress on your safety cover and cause the cover to rip or pull the anchors out of your deck.

If you are using a solid winter pool cover, lower the water level 3–4" below the bottom of the skimmer opening, unless you're using a skimmer plug. Skimmer plugs seal off the opening of your skimmer and keeps water out.

5. Turn Off System Components

Turn off the pilot, shut off the gas supply, and turn the gas valve to OFF, on your pool heater. For gas heaters with pressure switches hanging down connected to a siphon loop, disconnect the pressure switch to drain the copper tubing. Open the drain plugs on both intake and outlet headers, making sure your heater is free of pool water.

Shut off power to the pump, light and heater at the circuit breaker box. If you have a timer clock for your pool pump, turn it off and remove the timer trippers, also known as timer dogs. Disconnect power to any other electrical components that you don't want to operate during the winter, such as a salt system or chemical pump.

6. Add Winter Closing Kit Chemicals

closing chemicals to winterize your inground pool

For this step, we highly recommend using a chlorine-free pool closing kit. These kits come with everything you need, and are packaged according to the size of your pool. They include chlorine-free pool shock, a strong winter algaecide, a stain and scale preventer, a slow-release floater with oxidizing chemicals. Shocking the pool just before adding algaecide can be a problem, as high chlorine levels break apart the polymer chains in algaecide and render it useless.

If you are not using a winter closing kit, be careful when using chlorine floaters. They can sink, tip over, or get stuck next to a wall, which will stain a pool's vinyl or plaster surfaces during the winter. Use a high quality winter algaecide, a stain and scale preventer (chelator or sequestering agent) and some form of oxidizer to winterize your pool. Also, be sure to use non-chlorine shock, or only use chlorine shock 5-7 days before closing, to protect your winter algaecide.

If you have a mesh safety cover, we recommend using a pool enzyme product to help control algae growth during the winter. Also helpful is to check the water chemistry during mid spring, about a month before opening, and add another quart of algaecide or refill the floating chemical dispenser.

7. Drain Pump and Filter

Diatomaceous Earth (D.E.) filters should be opened up, and the filter grids should be hosed clean and inspected for rips or tears (mild staining is usually OK). Cartridge filters should have the cartridge removed and cleaned thoroughly. In both cases, after cleaning, reinstall the filter media back into the tank for winter storage. Lubricate any filter o-rings you come across in the process.

Adding antifreeze to your pump can damage the pump seal, so this should be avoided at all costs. It's much better to completely drain all the water from the pump and filter system, including the chlorinator and heater, or any other pool equipment containing water.

After blowing the lines, place your grid assembly or filter cartridge back in the tank for safekeeping during the winter. Secure the filter lid and clamp band securely before and after blowing lines. Loose filter clamp bands can cause the filter lid to blow off during start-up, with hazardous results.

8. Blow Out Water Lines

The best way to avoid pool freeze damage is to "blow out the lines" when you winterize your inground pool. Use a small air compressor at low psi or a high volume blower, like a Cyclone vacuum/blower or a powerful shop vac. Blow air through all equipment and pipes, both to and from the pool, and use pool plugs to prevent water from flowing back into the return lines. You'll also want to install a skimmer guard to absorb the pressure of expanding ice and keep your skimmer from cracking. If you want to add non-toxic pool antifreeze to the lines for added peace of mind, now is the time to do it.

9. Fill Water Bags or Lift Safety Cover Anchors

Safety covers will have a series of anchors around the pool, which are recessed flush against the pool deck while the pool is in use. Use an anchor hex key tool to twist the anchors and bring them up to the surface.

filled water bags

If you are using a solid winter pool cover that requires water bags to hold it in place on the pool deck, fill the water bags where they will lay. If filled elsewhere, be careful not to drag or drop the water bags as they are moved around the pool. Fill bags only 80% full to allow expansion as the water freezes. Keeping several small pails or pans of water around the pool is a good idea to keep birds and critters from poking holes in the pool water bags for a drink. If you want something a little more durable than thin water tubes, you can also try using a product like Aqua Block, which will hold up to many years of use.

Above ground pools should use an Air Pillow, also called a pool pillow or an ice equalizer pillow, to absorb the expansion of the ice and prevent the ice sheet on the surface from putting pressure on the pool walls. Only inflate the air pillows roughly 60%–80%, so you don't burst them.

10. Cover the Pool

Skim the pool again if needed, so the pool is as clean as possible. Clean off the pool cover too, to avoid bringing dirt and debris into your freshly cleaned pool. As you spread the cover over the pool, inspect closely for tears or rips. If possible, move these problem areas to the deck or close to the edge, and don't place your cover pump over the tears. Apply cover patches as needed — there are poly patches for solid winter covers, and mesh or solid patches for safety covers. Secure the cover with water bags (inground winter cover), straps and anchors (safety cover) or a cable-&-winch assembly (above ground winter cover), depending on the type of pool cover you're using.

That's all there is to it! Follow these steps, and you will winterize your inground pool in no time. Once it's closed, keep your pool cover as clean and dry as possible, and adjust as needed to keep it secure. Remember that solid pool covers with water bags are not safety pool covers, and can be dangerous for kids or adults who accidentally fall on top of them. Restrict access to the pool area during the winter, and keep an eye on the kids!

In The Swim makes every effort to provide accurate recommendations based upon current ANSI/APSP/ICC-5 2011 (R2022) standards, but codes and regulations change, and In The Swim assumes no liability for any omissions or errors in this article or the outcome of any project. You must always exercise reasonable caution, carefully read the label on all products, follow all product directions, follow any current codes and regulations that may apply, and consult with a licensed professional if in doubt about any procedures. In The Swim assumes no legal responsibility for your reliance or interpretation of the data contained herein, and makes no representations or warranties of any kind concerning the quality, safety, or suitability of the information, whether express or implied, including, without limitation, any implied warranties of merchantability or fitness for a particular purpose.