How to Winterize your Inground Swimming Pool

It’s fall, and the kids are back to school. Temperatures are dropping, and your swimming pool is getting cold! If you live where there are freezing conditions in the winter, closing your pool becomes an annual ritual. You can keep your pool open longer than you think, but at some point, you need to protect your swimming pool from the oncoming winter weather.
For more information on when to close your pool see When to Close your Pool.
It’s important that you take the time to close your inground pool properly. If you don’t, you can have big problems. You can damage pipes and pumps, your pool liner, or worst case, your entire pool can be destroyed by freezing water. If you don’t use proper chemicals, you may open up the pool the following year to an algae infestation that will take much longer to take care of in the Spring, when you’d rather be swimming.
Winterizing your pool doesn’t need to be difficult. You need to plan on spending a few hours over the course of about a week to go through all of the steps.
Note – the directions below are generalized to describe most swimming pools. Your pool may have requirements that vary from those described here.

Step #1: Test and balance your swimming pool water

About one week before you plan to winterize your pool, you should test and balance your swimming pool water. You want to make sure that your pool water is in good shape before you start the winterizing process. Make sure to reference the Winter Pool Closing Chemical Kit you are using to close your pool, but typical ranges are:

  • pH: 7.4-7.6
  • Total Alkalinity: 80-120 ppm
  • Calcium Hardness: 200-400 ppm
  • Chlorine: 2-3 ppm

Step #2: Clean your pool

Two or three days before you winterize, clean your pool. Remove all organic matter such as leaves and debris, and make sure to clean the sides of your pool and vacuum the surfaces. Phosphorus limiting products can help prevent algae growth over the winter. You want to remove as much as you can now to make sure your chemicals make it through the winter.

Step #3: Shock the Pool

Typically the Winterizing Closing Chemical kit will contain shock. Make sure that if you are using a chlorine shock, that you wait for the chlorine level to drop back down before adding any algaecide. The effectiveness of the algaecide will be negatively impacted by Chlorine.

Step #4: Lower the Swimming Pool Water Level.

Make sure you drop the water level below the skimmer and all of the return lines. This is typically twelve to eighteen inches (30 to 45 cm). Note: If you are using skimmer covers, you do not need to lower the water level in your pool. This can save lots of time and water. If you are draining your swimming pool and it has a separate main drain, this is likely to be the best way to drain it. Otherwise, you can use a submersible pump to remove the water. If you live in a warm climate where there is no risk of freezing, you can skip this step as well. Since your pool water has chemicals, it’s best to drain into the sewage system for your home. Some localities allow you to drain onto your landscaping, but there’s potential risks because of the chemicals in the pool water.
It’s a good idea to run your filters for a day or two to remove as much particulate and organic matter as you can. If you know your pool can be drained quickly, you can do this on the day that you close your swimming pool

Step #5: Backwash and Clean your filters and pumps.

Before closing down your pool for the year, you want to make sure these are cleaned out. Find a good place to keep it so you can find it in the Spring.

Step #6: Add Winterizing chemicals.

Add the algaecide and non-chlorine shock at this time. The best way to do this is to walk around your pool and add the liquid chemicals. This assures more even distribution.

Step #7: Drain water from your pool equipment.

One of the most important steps is to make sure to drain the water from your filters, pumps, heaters, and if you have one, your automated chlorinator. If you neglect this step, you can ruin these expensive pieces of equipment when the water freezes. This equipment should have winterizing plugs. Check their owners manuals for where these are and how to remove them. Put them in a safe place for storage over the winter.

Step #8: Install a winter pool cover.

The winter pool cover protects your pool from debris which could cause an algae bloom in the spring, and keeps the chemicals you’ve added for winterizing protected from an excess load which would eat them up before the winter is over. If you don’t have ties on your pool deck, use water tubes or pool cover weights to hold it in place for the winter. Install a pool cover pump to keep the water from building up on your pool cover.

Step #9: Turn off all power to pool.

As a safety precaution, it’s best to turn the power off to your pump and water heater at the circuit breaker. This reduces the risk of problems if something gets inadvertently switched on during the winter. You don’t want these systems to turn on unexpectedly!
Finally, check your pool water periodically during the winter. Peel back the cover slightly to take a sample, and also check for staining or scaling. If you see a problem starting, you should bring a sample to your pool pro to analyze the problem and take action.

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