How To Properly Winterize An Inground Pool (Close It Down)



Winterizing refers to closing down a swimming pool during the winter months; important if you live in a 4-season climate and want to protect the structure year-round.

To do this, you will have to follow a proper sequence of steps and make sure the correct maintenance chemicals are added to the water.

In this article, we’ll go over how to properly winterize your pool, step-by-step.

Why Winterize Your Pool?

Winterizing protects it from damage.

When water freezes, it expands. This can cause damage to not only the plumbing and equipment, but also to the vinyl walls of a vinyl liner pool.

Freezing aside, you also have to consider what happens when water sits stagnant for long periods of time, and why water circulation is so important for maintaining  a swimming pool in the first place.

With the filtration system disconnected during the cold months, the stagnant water in the pool will quickly become a breeding ground for bacteria and viruses, as well as algae blooms.

Properly winterizing the pool not only prevents these issues, but also makes your life easier when it comes to opening up again in spring.

When Should You Winterize Your Pool?

Winterizing is usually done in the fall.

Don’t wait until you find out there’s a frost warning or a winter storm about to hit. Leave enough time so the pool is properly closed before winter officially makes an appearance.

How To Winterize An Inground Pool (6 Steps)

Pool professionals charge anywhere from $150 to $300 to close a pool, so many pool owners take it upon themselves to learn the winterization process and save money.

There are a few things you’ll need over the course of this process, so we recommend gathering them on your pool deck before starting.

You’ll need the following:

  • Leaf blower or broom
  • Pool shock
  • Pool antifreeze
  • A Shop-Vac or sump pump with hose attachment
  • Pool skimmer Gizzmo
  • Duct tape
  • Wrenches
  • Winter pool cover
  • Cover pump
  • Pool pillow
  • Return jet plugs

Step 1. Prep The Pool

To prep the pool, start by clearing pool accessories and furniture from the deck, and use a leaf blower or broom to get rid of deck debris so it doesn’t blow into the pool.

Next, you’ll need to clean the pool, which includes:

  1. Skimming the surface to remove floating debris
  2. Brushing down the pool walls using your pool brush
  3. Vacuuming out any heavy debris like leaves from the floor of the pool  (their tannins can stain the pool floor if left over the winter months).

You’ll also need to remove any ladders from the pool structure using a wrench, as cold weather can damage them. Once removed from the pool, tilt them so that any remaining water in their tubes gets drained. 

Diving boards can be removed at your discretion (they usually hold up better in the winter), but if you have a slide you should also remove it for protection purposes.

Finally, If you use a solar cover, store it indoors for the winter. Not only will the cold weather cause it to become brittle and damaged, but sunlight will eat away at it as well.

Step 2. Balance And Shock

The next step is to balance the pool water and shock it.

Balancing the water is usually done weekly, and sometimes even more frequently, so you should be familiar with this process.

Test the water using either test strips, a liquid test kit, or a digital tester. Get all your levels where they need to be:

Once the water is balanced you’ll shock the pool to kill off any undesirable pollutants one last time.

This is usually done the night before you winterize, so the shock has plenty of time to be circulated and work its magic.

To shock your pool, you’ll need to add at least 10 times the amount of chlorine to the water as there is combined chlorine (typically 30ppm, but this should be measured) in order to reach “breakpoint”.

Step 3. Clean Out Your Filter

When winterizing a pool, you should always clean out your filter.

This preps it for the winter months so nothing left inside can freeze and damage the filter. It also allows you to have your pool up and running faster when you reopen it.

If you have a sand filter, you can do this by backwashing and rinsing it.

A cartridge filter will require you to open up the filter and hose down the cartridge (or even fully replace it if it’s too dirty).

If you have a DE filter, you’ll have to backwash it, and then open it up and hose it down as well.

Step 4. Protect The Suction Lines

Now you’ll want to clean out the pool’s lines so they don’t crack in cold weather.

Before starting, either drain the pool just below the skimmer, or block the skimmer using something of similar size (a rectangular tupperware lid works well).

Now follow these steps:

  1. Remove the skimmer basket for indoor storage.
  2. Turn on the pool pump and run it for 5 to 10 seconds, just enough time for it to suck in any remaining water from the suction line.
  3. Use your Shop-Vac to suck up any residual water that’s left in the skimmer and make sure there’s no water leaking in from the pool.
  4. Pour about a gallon of pool antifreeze into the skimmer. This will make its way into the suction lines, protecting them from freezing up over the cold months.
  5. Screw the pool skimmer Gizzmo to the suction line inside the skimmer, protecting the skimmer from freezing if water gets inside. The water will enter the Gizzmo instead, and damage that, rather than your entire skimmer structure. 
  6. Finish by adding a half gallon of pool antifreeze into the skimmer (submerging the Gizzmo), and put the lid back on.

Step 5. Blow Out The Return Lines 

Like the suction lines, this process involves clearing the return lines of any water that can freeze and damage them.

Here’s how to do it:

  1. Remove your pump’s lid (make sure the pump is off) and pour a half gallon of pool antifreeze in it.
  2. Attach your Shop-Vac to the pool’s return lines using a hose extension and duct tape. Turn it on so it blows air into the return line, pushing water out of the return jets.
  3. Unscrew and remove the return jets and replace them with return jet plugs. These block the lines so nothing can enter the pool.
  4. With the return lines plugged up, you can remove the attachment hose from the Shop-Vac, but leave it connected to the return line plumbing.
  5. Pour a gallon of pool antifreeze into the attachment hose, so that it enters the return line. Reattach the return line to your filter.
  6. Finally, remove the drain plugs on the pump and filter, as well as the filter’s pressure gauge and the pump’s sight glass. Store these somewhere safe for the winter.

Step 6. Attach Your Pool Cover

There are a few different types of winter pool covers you can use on your pool. 

A vinyl tarp is the cheapest cover you can get and they’re weighed down by water bags. They’re made of vinyl that can withstand snow and water, but they usually only last a season or two.

Solid vinyl safety covers protect most inground pools these days. They are strapped to the deck and provide safety, while blocking debris and sunlight from entering the pool.

Whichever cover you use, make sure you use a pool air pillow under it, and a cover pump on top of it.

The pool pillow protects the pool walls from damage. In case the water freezes, the pillow will redirect the ice from expanding out, and it will expand up into the cover instead.

A pool cover pump is essential for moving water off the cover. Not only does it protect the cover from water damage, but stagnant water can introduce algae growth and also be a breeding ground for mosquitoes.

Obviously, you won’t need the pump if everything is frozen over, but it’s a smart tool to use when you have water on the cover.

A Word On Opening Your Pool

If you winterized properly, opening the pool won’t be nearly as labor intensive – but you may still need to do some work to bring the water back to a swimmable condition.

Start by using a cover pump to move water off the winter cover, and then remove the cover. At this point your water should either be pretty clean, or pretty green.

Go around the pool, removing the plugs and replacing the return jets. Remove the Gizzmo in the skimmer, and put the skimmer basket back in.

Next, put the drain plugs back on the pump and filter, as well as the pressure gauge and sight glass. Inspect the pump lid O-ring for any damage. Replace if needed, or lube it up if it’s still ok to use. Secure the lid, and turn on the pump.

If you don’t see bubbles coming out of the return jets, turn off the pump and prime it by pouring water into the pump basket, then turn it back on.

The only thing left to do is test the water, and add any chemicals that are needed to make it 100% clean and ready for swimming. If the pool is still green, you may need a few rounds of shock treatment.

Pool Hibernation Is Real

Learning how to winterize a pool can be intimidating, but hopefully we’ve made it easier to do on your own.

Not only will you protect your pool and the water in it, but you’ll save money, and the pool will be ready for swimming when reopened.

Categories: Pool Care, Pool Maintenance