How to winterize a pool in 6 steps



The end of summer means you have to start preparing your home for the freezing temperatures of the winter months. This prep includes everything from stocking up on seasonal equipment to ensuring the heating system is in order. These may not be the most exciting tasks, but getting them out of the way before winter sets in allows you to live comfortably and stay warm when it gets chilly outside.

Your swimming pool, whether an above-ground or an in-ground pool, is no exception. Thorough pool maintenance is essential for all pool owners to keep a pool healthy and usable. If you skip the process of winterizing, you run the risk of letting any remaining water freeze and expand, which can damage pool equipment or otherwise durable vinyl liners. Neglecting or doing the steps improperly can also lead to the buildup of unwanted residue from algae and bacteria.

To avoid an unpleasant transition into spring, we suggest making pool maintenance for the winter a priority. In this article, we take you through the six steps to winterize your pool properly. Summer will be here before you know it, and then you’ll be reopening the swimming pool again!


When should you winterize your pool?

You can begin the pool-closing process soon after your last swim of the season. If you start prematurely, your pool could become a breeding ground for algae because these organisms prosper when temperatures are high.

The appropriate time to start closing the pool will vary depending on where you live. A good starting point is when the temperature drops to 65 degrees Fahrenheit and continues to dip. This temperature greatly diminishes the risk of algae taking over the pool.

Waiting until the mercury drops to close the pool also gives you sufficient time to test and balance the water. If you live in a warmer climate where the temperature rises above 65 degrees Fahrenheit in the winter, you can also use this period to test and balance the pH levels of the water. Doing so keeps your water clean and clear.

Keep in mind that this is a multistep process that spans a few days, likely taking a week or so from start to finish.


How to winterize a pool in 6 steps

Winterizing the pool may not be a two-minute task, but it will be worth the effort next spring. Proper maintenance every winter also goes a long way in keeping the pool in good shape for years to come. Here, we break down the winterization process into six steps that you can check off your to-do list one by one.

Step 1. Thoroughly clean the pool

It goes without saying, but the first step is to clean the pool. Bring out your supplies and get started. Use your skimmer to get any floating leaves or debris off the surface and out of the way. We suggest vacuuming the entire pool manually or with a robotic pool vacuum to reach the depths. Be careful not to neglect the pool walls and floors. Use a pool brush rigorously. Don’t forget to clean your pool filter grids too.

This cleaning is of utmost importance because it makes subsequent steps, such as balancing the water chemistry, much easier to perform. A clean pool also leaves no fodder for algae and mold to take charge throughout the winter. You can safely return to the pool when the sun is out again in a few months.

Because winterization spans a few days, we suggest keeping the pool covered when you are not actively carrying out the process. This cover prevents it from getting dirty so that you don’t double your workload.

Step 2. Adjust the water chemistry

Balanced pool water is less likely to damage your pool liner and equipment when not in use. It also wards off any potential for algae to overtake the pool. There is little risk of corrosion or scale buildup when the water in a swimming pool is balanced. It is important to test and balance for the following scales:

  • Alkalinity: This must ideally be at around 125 parts per million (ppm), but within the range of 100 ppm and 150 ppm is acceptable. 
  • pH: Aim for pH levels between 7.2 and 7.6.
  • Hardness: Ensure that calcium hardness is between 175 ppm and 225 ppm.

Testing the water is easy with the availability of test strips and water-testing kits. If you live in an area experiencing warmer weather during winter, test the water every few weeks.

Upon testing, if you find that any of the above levels are outside their recommended range, balance them out using the appropriate increaser or reducer. Be careful to balance the alkalinity before the pH, and then the calcium hardness. We suggest aiming for the higher end of these ranges because the levels are bound to decrease over time since you will not be adjusting water chemistry during the off-season.

Step 3. Lower the water level

This step is contingent on a few factors. If you live in an area where the water is likely to freeze, and you do not use a cover plate for your skimmer, lower the water level in the pool. Be careful not to drain all the water from an above-ground pool because this can lead to your vinyl liner drying up.

If using a mesh cover, drop the water level a foot below the skimmer. Half a foot below the skimmer works fine for those using solid covers.

Step 4. Drain pumps, filters, heaters, etc.

All pool equipment must be drained to prevent the water from expanding as it freezes. Use a blower to remove the water from the pool lines and use expansion plugs to plug them. You can also remove the lines and let the water flow out on its own. Air-dry the pool lines to avoid any possibility of mold growth. Store the lines in a cool, dry place.

Pool filters, pumps and heaters have drain plugs you can use to drain the equipment. This process is relatively simple. Take off the filters, clean them, and store them indoors along with the pool pumps. 

If winterizing an above-ground pool, you must remove the hoses instead and seal all outlets.

Step 5. Add algaecide and shock

Despite taking the requisite steps to avoid algae and bacteria growth, you may want to be extra careful. You can choose to add algaecide to get rid of any algae and add pool shock to kill the bacteria. Add both pool chemicals right before closing the pool for the winter.

Pool shock comes in various types, such as fast-dissolving shock. Be sure to read the instructions for the one you are using and follow the instructions carefully. Add the right amount for the size of your swimming pool and spread it across the pool. Be careful not to use chlorine shock and algaecide simultaneously. If you are using non-chlorine shock, this is not an issue.

Step 6. Cover the pool

Finally, it is time to install a pool cover. Ensure that the pool cover shields the entire pool and secure it in place. You can do this using some combination of a cable, a winch and a few winter pool cover clips. Use as many as you need so you are free from any worries of the cover unfastening. Steer clear of using objects that could damage the liner if they fall into the pool.

Covers come in two types: safety and winter. Safety covers offer the most security from not only debris but also anyone accidentally falling into the swimming pool. Winter covers are less secure but more convenient to fix. Regardless of the cover you use, it should be fixed well and not have any gaps or holes.

Anchoring air pillows are necessary for above-ground pools because they can absorb any ice expansion inside the pool and prevent snow from weighing down on the swimming pool.


Pool winterizing FAQ

To clarify doubts about this six-step winterization process, we have answers to some commonly asked questions.

What chemicals do you put in a pool for winter?

In addition to testing for total alkalinity, pH and hardness — and balancing them if needed — you must check your chlorine level (if you use it) and ensure that it is between 1 and 3 ppm. If you do not use chlorine in your pool water, make sure that the sanitizer is at the appropriate level. Finally, shock the pool a few days before you close it. Algaecide is an optional winterizing chemical if you want increased protection against algae.

How far down do you drain your pool for winter?

Draining the pool is only required if you live in an area with cooler temperatures where the risk of freeze damage is real. As a rule of thumb, keep the water level below the tile border, the bottom of the skimmer, or whichever is lower. Your cover and pool surface determine the exact level to which you must drain the pool water.

Do you empty above-ground pools for winter?

When winterizing, emptying an above-ground pool is not a good idea. It can cause your vinyl liner to dry up, reducing its durability.


Protect your home systems from expensive repairs with Cinch

Now that you’ve got the winterization of your swimming pool out of the way, it’s time to turn your attention to the rest of your house. We have protection plans for your appliances and built-in systems, as well as complete home warranties. Let us take care of your home systems — including your swimming pool — so that you can enjoy the winter without worrying about costly repairs. Get a quote from Cinch Home Services today!


Protect your in-ground or above-ground swimming pool during the off-season by following this six-step winterization process.