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Closing an Inground Swimming Pool? How to Winterize a Pool for an Easy Spring Opening

I'm a tool guy and love to put tools through the test. When I find a tool that can make life's every day projects easier, I like to share.

The finished product.

The finished product.

How to Winterize an Inground Swimming Pool

Closing an inground swimming pool is a lot more challenging than opening an inground swimming pool. The challenge is removing all the water properly from the pool equipment and plumbing as well as winterizing it for the freezing temperatures that are on the way. If you winterize your pool properly in the fall, a spring opening will be a snap, and you will be the envy of your neighborhood pool owners.

I took a step-by-step approach with many pictures so I could walk you through the process as much as possible without physically being there to help you. As I closed my pool this fall, I took very detailed pictures to help me animate the procedure so you won't run into any problems. If you have any problems or questions, just shoot me a comment, and I will answer it ASAP because, at this time of the year, time is of the essence.

Step 1: Preparing for Winter

First and foremost, your pool needs to be totally clean and the pH, alkalinity, hardness, and chlorine need to be set to their ideal levels. This is the most important step because if you close a dirty pool, it will only get worse throughout the winter. So clean it, set it, and forget it!

Step 2: Buy a Winterizing Kit

When you purchase a winterizing kit, buy one that will winterize the amount of water you have in your pool. If you buy a kit that is too small, it will be wasted money, so know your pool's water capacity and buy the right kit.

I had to buy two kits this year because the company I buy my winterizing kits from stopped selling the large kits for 25,000-gallon pools. You'll aso want to purchase a disposable floating chlorine dispenser that will float around your pool when the pool isn't frozen- it will keep the water clear, and it helps kill any algae that attempt grow on the warm spring days.

Step 3: Start Adding the Winterizing Kit

It's best to follow the instructions on the winterizing kit; that's why they're there. You need to add the PhosFree to your pool water first to remove any phosphates in the water; by removing the phosphates in your pool water, you will stop the growth of algae throughout the winter. Add the PhosFree a week before closing your pool; just pour it into the filter and let it do its thing. I recommend starting the process one weekend before closing your pool.

Step 4: Add the Rest

Start by adding the bottle of metal free to the pool water, just sprinkle it across the top of the water, do not add it to the filter. The metal free will remove any damaging metals in the pool water, this will prevent any stains or water discoloration in the off-season.

At this point, your pool water should be clean, free of metals and phosphates, the chlorine level should be almost perfect, and your pH, alkalinity, and hardness levels should be at the ideal levels. Now it's time to drain the pool.

Step 5: Lowering the Pool Water

According to some winterizing kits, you should lower your water level about 18 inches from the top of the skimmer. An easy way to determine if the water is low enough is to lower it to the bottom of the return jets/ lines. When you lower the water level below the return lines, it allows the water to drain from them as well, so lower the water to just below the return lines (see the pictures for details).

Use the pool pump to lower the water level, turn the diverter handle to backwash, then turn the inlet lever to draw water from the bottom drain of the pool and not the skimmer. This will allow you to lower the pool water well below the skimmer without sucking air into the filter. While the pool water is draining, start removing the jet nozzles on the inlet lines, skimmer basket, ladder, and handrails. If you have a safety cover, start pulling up the anchors on the pool deck and start unwrapping the pool cover that you have in storage.

Once the water is below the return lines, you can shut off the pump. But before you shut the pump off for the winter, you need to suck the remaining water from the skimmer. The best way I found to suck the remaining water from the skimmer is to use the pump one last time. When you're ready to stop pumping water from the bottom and the water level is where you want it, turn the lever on the inlet pipes to skimmer until you hear the pump suck air, then turn off the pump, but leave the inlet lever on skimmer.

Now is a good time to add antifreeze to the skimmer; the water level should be low enough in the skimmer so that when you look down into the skimmer you cannot see any water in the pipe, if there is no water in the pipe, add your pool antifreeze, about 1 quart to 1 half gallon. Install the gizmo with Teflon tape wrapped around the threads and then add about 1 quart to 1 half-gallon of antifreeze to the skimmer housing so that it surrounds the gizmo.

The gizmo is installed for two reasons; one is to stop water from reentering the skimmer lines during the winter and two, it is air-filled, so that if water does enter the skimmer and freezes, the ice will expand and crush the gizmo and not split or crack your skimmer housing.

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Once the gizmo is installed and the antifreeze is all set, take the skimmer cover and wrap it in a plastic bag; just take a plastic bag and put the skimmer cover in it, then wrap it so that the top of the cover is wrapped tight and the remaining part of the bag is on the underside of the cover. Next, install the skimmer cover on the skimmer (see pictures)- this plastic bag will help keep out rainwater during the off-season.

Clean Your Pool Steps Before You Close It

Install an air line fitting on the bottom of your filter basket housing, remove the drain plug and install the air line fitting.

Install an air line fitting on the bottom of your filter basket housing, remove the drain plug and install the air line fitting.

Attach an air line from your compressor,  remove the water from the return lines, make sure the diverter handle is in the filter position.

Attach an air line from your compressor, remove the water from the return lines, make sure the diverter handle is in the filter position.

Step 6: Blow Out the Lines With Compressed Air

Blowing out the lines sounds daunting, but it's quite simple. On the bottom of the basket housing at your pool pump, there is a little plug.

  • Remove the plug, and install an air line nozzle so you can attach an air line easily (see pictures for more detail). Drain the basket housing of water, drain the pool pump from the bottom drain and unscrew the vent at the top of the pump to allow air to enter the top of the pump and let the water drain faster out of the filter.
  • Once the pump and the filter basket housing are drained, reinstall the drain cap on the filter, the vent cap, and install the air line fitting to the bottom of the basket housing. Clean out any leftover chlorine in the self chlorinator. Set the diverter handle to filter and add compressed air to the filter at the air line fitting.
  • Watch the water drain from the return lines; when the water stops coming out of the return lines, shut off the compressed air and cap the lines with special caps designed to keep water out during the off-season. These caps have rubber o-rings, but I like to use Teflon tap on the threads for added protection; I also add Teflon tape to the threads of the gizmo for added protection.

Step 7: Add Pool Antifreeze to the Pump

The pump and filter should be drained by now, and the pump basket housing should only have a little water in it; if you think there is still too much water in the basket housing, just scoop it out with a plastic cup.

  • Add about 1/2 gallon of pool antifreeze to the pump basket housing and reinstall the cover. Add pool antifreeze to the self chlorinator, about 1 half gallon, then reinstall the cover. You should only need about 2–3 gallons of pool antifreeze to close the pool unless it's a huge pool; I am basing the capacities on a 23000-gallon pool.
  • Place the handle of the diverter valve in a neutral position between filter and waste, or something like that, just don't leave the lever in one of the designated positions because there is still water in the diverter, when you put the handle in a neutral position it will allow the water to freeze and expand without cracking something internally on the diverter valve (see picture).
  • After the pool pump has been winterized, remove the drain cap from the bottom of the sand filter or DE filter just to finish draining the water from inside the tank. The filter is saturated with water, and I like to let it drain thoroughly so I will leave the drain cap off for 24 hours. If you have a filter cartridge, remove the cartridge and power wash it, then store it for the winter.