How to Winterize an In-ground Swimming Pool

If you own an in-ground swimming pool and live in a climate where freezing temperatures are normal, you will need to winterize your in-ground pool to protect it during cold months.

Why the protection from winter?

Frozen water can damage your pool and make it difficult to clean after the winter.

Guide to Winterizing your In-Ground Swimming Pool

Gather Supplies

First try and find any chemicals and supplies used from previous years such as the cover, cover weights, skimmer plugs (also called gizmos sometimes), anti freeze and flotation devices for cover.

For a full winterization, you will also typically want to use an air-compressor to blow our your swimming pool lines.

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. Add a winterizing chemical kit to your water will help keep it blue and clear for the next season. Be sure to follow the manufacturers instructions for the kit.

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 multi port 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 NO run the pump more than a second or two because you can burn out the seal very quickly. You should let the chemicals run out of your feeder so that no chemicals are left in it.

Drain the Other Equipment

You will now be able to drain your chemical feeder and automatic cleaner pump, heater and 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 easily be found in the spring. It is a good idea to take the pressure gauge inside for the winter.

If left outside, water can collect in its tube which can freeze and cause damage. DO NO put the plugs back on the equipment. If equipment should get water in it, the plugs will prevent proper draining.

1. Blow out the lines at the pool equipment

Use your air compressor or a shop vacuum to blow out the lines if possible and plug them. This is a two person job.

2. Heater Preparation

Pull the drain plugs on the front and back “headers”. Not all heats have multiple drain plugs. If you have an air compressor, try to blow any remaining water out of the heater. It is generally not recommended to remove a heat exchange or burner try.

3. Return Jets and Skimmers

Remove any return jet fittings along with skimmer baskets and weirs. (Weirs are the little flappers at the throat of a skimmer that function as a door)

4. Blow out Return Lines

Use an air compressor to blow out all the return jet pipes. Make sure to keep the air blowing until the air is visible coming back into the jets of the pool.

Put a plug in the fitting under the water when you see the bubbles blowing at full force. Doing this right can get over 95% of the water out of the return lines.

5. Blow out suction lines

Also use an air compressor to blow out all the return lines. Use a Gizzmo-style screw to plug the skimmer when bubbles are visible. Be very careful to get the Gizzmo-style screw installed properly. Put PTFE tape on the Gizzmo threads before installing to ensure a tight seal.

You can also use black rubber-type plugs instead. They will work if there is something in the skimmer to allow for water expansion when it freezers.

Usually a closed plastic empty soda-type bottle will work. It is crucial that you have those bottles in place to avoid cracking your skimmers.

6. Check Water Level

There are differing opinions on this topic. In the New England area many pool owners do not drain any water out of the pool. This works if all the lines have been effectively blown out and sealed as described. If a pool has ceramic tiles it is recommended to drain the water a few inches below them, but not further.

Final Step to Winterize – Cover the Pool

Last but not least, remember to cover the entire pool. This will keep debris form 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 keep in over the course of time. Both are good choices.

Inspect the cover before installing. When inspecting the cover, if you find any rips or tears try to patch or repair them ahead of time.

A swimming pool patch tape or heavy duty duct tape cane be used to patch lightweight covers. A vinyl pool patch will be needed for vinyl covers. Place the cover on the pool.

We hope this guide to winterize your in-ground swimming pool was helpful. Read more guides at to become a total DIY pro of your own swimming pool.