How to Winterize Your In-Ground Swimming Pool

Snowman Winter Holiday Vacation in Beach Resort Hotel Swimming Pool
YinYang / Getty Images

If you own an in-ground swimming pool and live in a climate where freezing temperatures are normal, you'll need to winterize your pool to protect it during cold-weather months. This will protect it from damage due to freezing water and keep it as clean as possible for the next season.

Check Your Chemistry

The first step in the winterization procedure is to make sure your water chemistry is balanced, including the pool's pH, total alkalinity, and calcium hardness. Doing this will protect the edge of the pool from staining and etching. Adding a winterizing chemical kit to your water will help keep it blue and clear for the next season. Be sure to follow the manufacturer's instructions for the kit. Do not use a floater that contains a strong oxidizer (chlorine or bromine) because the floater may stick against the pool wall and stain or bleach it.

Protect the Skimmer

When water freezes, it expands. This can cause great damage to your pool, pool plumbing, and its filter system. To avoid this, lower the water below the mouth of your skimmer(s). This will get the water out of the throat of the skimmer which can be easily damaged if water were to freeze there.

Another option for vinyl-liner pools is to put an Aquador over the mouth of the skimmer. This is a plastic dam which holds out the water from the skimmer, allowing you to leave the water level up for the winter. This will help in supporting your cover and also help keep the liner from floating on the water's surface. 

Use a Gizzmo to seal the line. This device is a hollow tube that will collapse if water should get into the skimmer and freeze. Be sure to put Teflon tape on the threads of the Gizzmo to make a seal and to ease removal in the spring. It is usually impractical to put a plug in the main drain if you have one, but its extreme depth will normally protect it from freezing

Clear the Plumbing

Blow out the water from your plumbing lines. You can do this using a shop vac. Use the discharge of the shop vac to blow water out of each line from the filter system. As the water is purged from each line, you will need to put a plug in the lines at the pool end. Some fittings will allow for a threaded plug, which is best. Be sure to use a plug with a rubber gasket or "O" ring to make a seal, or the water may fill the line back up. If your fittings are not threaded, then use a rubber freeze plug.

Drain the Filter

The filter should have a plug at the bottom that will allow it to drain. Be sure to open the air relief valve on top if you have one. Put the multiport valve in the closed or "winterize" position and remove the pressure gauge. Drain the pump. There may be two plugs to remove here.

After draining the pump, turn it on for a brief second to get the water out of the veins of the impeller. Do not run the pump more than a second or two because you can burn out the seal very quickly. You should have let the chemicals (chlorine/bromine tablets) run out of your feeder so that no chemicals are left in it. Leaving chemicals in your feeder over the winter can cause damage to it and other equipment.

Drain the Other Equipment

You will now be able to drain your chemical feeder and automatic cleaner pump, heater, and any other filter equipment that has water in it. If you put all the plugs that you have removed from the pump strainer basket, they will be easily found in the spring. It is a good idea to take the pressure gauge inside for the winter because water collects in its tube which can freeze and cause breakage. Do not put the plugs back on the equipment. If equipment should get water in it, the plugs will prevent proper drainage.

Cover the Pool

Last but not least, remember to cover the entire pool. This will keep debris from falling into the pool as well as keep pool water clean. Look for a mesh or solid-surface safety cover. Mesh covers are lighter than solid-surface ones and easier to install, but they also will allow some water and debris to seep in over the course of time. Both are good choices, pool experts say; it's all a matter of personal preference.