With temperatures starting to take a dip all over the country, many of the swimming pools we spent countless happy hours during the summer are ready to be closed. But closing a pool for the winter means more than simply throwing the cover over the top of it. Proper water chemistry is essential if you want to protect your pool and make next year’s spring opening tasks easier.

Why Pool Water Chemistry Matters Prior to Winterizing a Pool

A variety of nasty issues can plague your pool if the pool water isn’t properly balanced before winter arrives.

  • Low calcium levels in a gunite pool can damage the plaster and cause etching on the surface of your pool. Low levels of calcium can also destroy vinyl pool liners.
  • Low pH levels lead to surface corrosion on gunite pools and wrinkling in vinyl liner pools.
  • High alkalinity levels mean having to deal with cloudy pool water in the spring and make it that much more difficult to clear the water.

With the right balance of chemicals in your pool water, you’re effectively protecting your investment before problems begin. You’ll have peace of mind in knowing that when you’re ready to take your first swim of the season that you’ll pool will be in good working order.

No Special Chemicals Required for Winterizing Your Pool

The good news is that you already have everything you need to winterize your swimming pool. This process should be started about one week prior to closing your pool.

1. Raise the Alkalinity

During the summer your ideal pool alkalinity is between 120 and 140ppm. Because you won’t be frequently monitoring your pool’s water chemistry, the alkalinity should be increased to between 150 and 175ppm. This is done for the same reason why the pH levels are increased – alkalinity levels tend to decrease in stagnant water over long periods of time.

2. Raise the pH

During the summer, swimming pools traditionally have a pH balance between 7.2 and 7.6. During the winter, it’s recommended that the pH be raised to 7.8.

This is because your pool water will be stagnant over the winter months. Over the days and weeks that your pool is closed, your pool’s pH will naturally lower itself. By raising the pH levels before pool closure, you’re offsetting the natural pH decrease that occurs over winter.

3. Raise the Calcium Levels

Unlike your pH and alkalinity, your calcium levels won’t decrease as the fall and winter months pass. But it’s still a good idea to ensure that its levels are adequate to prevent any unwelcome surprises once spring rolls around. Generally raising your calcium hardness levels to above 200ppm is all that’s necessary to prevent calcium from eroding your pool.

4. Shock Your Pool Water

Several days prior to closing your pool, add a shock product to your pool water to kill any existing algae and bacteria. Most experts recommend finding a product with a minimum of 65 percent sodium hypochlorite, or you can choose a non-chlorine alternative of the same strength.

After a few days, your chlorine levels should return to anywhere between 1 to 3 ppm.

5. Consider Adding a Winterizing Algaecide

Algae can wreak havoc on your pool over the winter. Not only can it cause your pool water to become green or cloudy, but it often results in unpleasant odors and it can even clog up your pool filter. Winterizing algaecide can be added to your pool once the chlorine levels are sitting between 1 and 3 ppm

Remember that once your pool is closed, the pool water chemistry can’t be changed. This is because your pool water isn’t being circulated so the chemicals cannot be evenly distributed throughout your pool. Putting in the work now means saving your head headaches and potential problems later on.

Need help with winterizing your pool? Save yourself the time and hassle by enlisting the help of the pool experts at The Pool Doctor of Rhode Island, and give us a call today!


The Pool Doctor of Rhode Island is the leading full-service pool and spa company in Rhode Island. Their business had its beginnings in 1987 when co-owner Ron Leclerc began selling pool supplies out of the back of his Camaro. In 2001, Ron and his wife Debbie opened their 7,000 square foot facility in Coventry. This extensive and beautiful showroom is the result of years of hard work and represents a long-standing tradition of excellence and commitment to giving Rhode Islanders the best pool and spa service, advice, and products.

From installing vinyl liner inground swimming pools to selling gorgeous Dimension One hot tubs to offering free water-testing and professional service in their store, The Pool Doctor of Rhode Island is your place for everything pool and spa. They are a proud BioGuard Platinum Dealer and also offer a huge selection of other brands of swimming pool and hot tub supplies, including Loop-Loc Pool Safety Covers, above ground pools, and Hayward equipment. But, more than anything, The Pool Doctor of Rhode Island strives to give their customers a wonderful experience from beginning to end. 

Visit The Pool Doctor of Rhode Island at 2200 Nooseneck Hill Road in Coventry or at splashtime.com or give them a call at (401) 392-1300. They serve all of Rhode Island, including Coventry, West Greenwich, East Greenwich, North Kingstown, South Kingstown, Exeter, Richmond, and Hopkinton.