How to Winterize Inground Pools in 12 Basic Steps

Winterizing in-ground pools is necessary in areas of the country where the temperature drops into the low thirties for an extended amount of time during the fall and winter months—cold enough for water and the ground to freeze.

If left open and operating, a swimming pool has water circulating through its pipes; when this water freezes and expands its mass, it can burst the pipes and damage equipment like the filter or pump! That’s why it critical to properly close down your pool for winter. Here’s how in 12 basic steps.

1. Clean your pool. 

To start, it’s a good idea to get your pool spic and span. Remove any toys or accessories from the water. Skim the surface with your pool net, brush down the walls to dislodge any debris, and vacuum your pool or run your automatic cleaner for a few extra hours. Empty out the skimmer and pump baskets.

2. Test and balance the water.

Using a pool test kit, check the water to make sure it is balanced. For gunite pools to be at the proper levels, the ideal range for pH is 7.4 to 7.6., and for alkalinity the desired level is 80 to 120 PPM (parts per million). If one or both are not in range, adjust the chemical levels as needed. Once your current water condition is where it needs to be, you are ready for the next step.

3. Drain water from the pool equipment. 

To prevent freeze damage, you need to remove water from certain items of pool equipment. Begin by unscrewing all of winterizing plugs on equipment as follows: one on the filter; two on each pump; one on the chlorinator; and one to two on the heater (check your owner’s manual for specs). Once the plugs are removed, the water will be able to drain out within a few minutes.

4. Reduce the water level. 

It’s time to drain some water from your pool; never drain all of it! You will need a submersible water pump. One option is to drain the water to approximately two inches below the return line; typically, that’s about 12 inches from the top of tile line. Another option, which conserves water, is to drain the water down only a couple of inches below the tile line, and then use stand pipe to blow out the water from each line. Now, if you have an automatic pool cover, drain the water level to about two inches below the “throat” of the skimmer.

5. Empty all water from the return lines. 

To prevent damage to your pool, it is critical to blow out the lines with air that expels every bit of water from them. If you do not understand your pool plumbing system and the role of each valve and drain and how to operate them, or, if your pool has a complex configuration—such as a spa, pressure cleaner, or water features—you might be better off hiring a pool-service tech for this task. You will need either an air compressor, a commercial-type air blower, or a powerful, heavy-duty shop vac. Whatever you use for a blower, it will need to have either a hose attachment or PVC adapter (or other means) so that it will attach and fit into the pool pipes without air escaping. Use your blower to force out all of the water from each and every return line throughout the pool, including cleaner lines.

6. Plug each return line and the skimmer.

Once water has been expelled from each of the return lines, you need to prevent water from re-entering them. For this, you will need freeze or winterizing plugs that you insert into each return line. For the skimmer, use a protective device known as a gizzmo that screws into the throat of the skimmer to protect it from freeze damage.

7. Airlock the main drain. 

Using the same equipment you used to blow out your return lines, it’s time to expel water from the main drain line. Turn the valve for the main drain to the open position. Then, blow air backward through the drain. Once you see bubbles coming up from the drain in the pool, turn the control valve to the off position. Then, shut off your blower or air compressor. Now your main drain is air locked.

8. Shock your pool. 

Even if you don’t regularly shock your pool water, doing so for winterization is a smart move. Adding this treatment—a form of super chlorination—helps rid the water of organic materials and stops most any kind of microbes from growing and reproducing through the winter months. Next year when opening your pool, the water will be in better shape and require less time and effort to make swim-ready.

9. Add an algaecide. 

An algaecide is a chemical that not only kills algae that is currently growing in the pool, but also prevents future growth. Consider purchasing winterizing algaecide that has been formulated to remain stable in cold temperature and with changing pH levels. Adding this chemical is a simple step that enhances the benefit that comes with shocking your pool—water will be cleaner when you open your pool in the spring.

10. Clean the pool filter. 

A pool with a clean filter is a happy pool. Unless you have you have a sand-type device, you will need to clean the filter elements as regularly do. Take the time to do a thorough housekeeping job on this winterizing task, and you will be rewarded come spring: When opening your pool and the water begins circulating, you won’t have to worry about a clogged filter failing to trap dirt and debris.

11. Cover your pool.

Use a clean, durable pool cover, and make sure it is properly attached. A good choice is a winterizing cover that comes equipped with an automatic pump; this pump will sense when too much water collects on the cover surface and turns on to pump it off. Another good choice for closing your pool is a quality safety cover that fastens to the deck. Throughout the winter, use a leaf blower to keep the cover free of debris.

12. Cut power to the pool.

It’s a good idea to turn off the power to the equipment. To ensure that all of it remains off throughout the winter, turn off the specific circuit breaker for your pool equipment. This is a particularly important if any of your pumps have freeze protection that automatically kicks on a pump when the mercury drops to 32 degrees.

These steps provide a general overview of what’s involved in shutting down a gunite pool. It’s important to note that depending on your pool’s configuration, features, and equipment systems, there can be variations in these steps, sequence, and the exact process.

Be sure to consult the owner’s manual for your pool equipment, and if it is your first time winterizing a pool, you may want to hire a professional to go through the process at least once with you.