Updated 9/5/2023

September has arrived and in many parts of the country, it’s nearly pool closing season.

Unless you hire a pool service, there are several things you’ll have to do to get your pool ready for winter.

Here, Pool Central addresses some common pool closing questions.

When should I close my pool?

The best time to close a pool is when the pool water temperature dips to at least 60 degrees. Algae has a much harder time growing at this temperature. Close your pool too early and you may actually incubate algae in the water before it cools significantly.

Additionally, pool chemicals only last an average of five months. In colder climates, that means your chemicals could fail well before the weather improves. For this reason, you may want to delay your pool closing a bit longer. Whether you close your pool sooner or later, plan to put the pool to bed before nighttime temperatures start to fall below freezing.

Should I clean the pool before I close it?

Yes - don’t put your pool away dirty! Get it ready for winter by vacuuming, brushing down the walls and skimming.

By getting your pool as clean as possible now, you’ll have less trouble and work getting it ready for swimming next year!

Do I need to add chemicals to my pool before closing it for the winter?

When closing a pool for winter, you'll need to balance the pool water chemistry for proper pH, alkalinity, chlorine and calcium values. Test and balance your water. Balanced water is less likely to damage your liner and grow algae.

In addition to balancing your water, it’s advisable to shock your pool to reduce the chance of algae growth. If you want, you can apply an algaecide to help minimize green water in the spring.

Do I have to lower the water level in my pool?

Whether or not you need to drain some of the water out of your swimming pool depends on several factors, including the pool’s type and construction.

A soft-sided metal frame pool or inflatable swimming pool should not be exposed to harsh weather. Protect your investment by draining your pool and allowing it to dry. Dismantle it and store it indoors for the winter.

The water in your steel frame above ground pool actually helps keep the liner in place and prevents the pool wall from collapsing. However, pool owners typically bring water levels below the skimmer and return lines to prevent skimmer damage.

Whether and how much you should drain inground swimming pools is a complicated question. It depends on whether your pool has a liner or tile and also what kind of winter cover you use. Refer to our blog “Do I Have to Lower the Water Level in My Pool for the Winter?”, or contact a pool closing service for advice and assistance.

Do I need to drop, lower or remove pool lights?

It depends on what kind of lights you have. Most modern LED lights and sealed lights can stay in place. However, if your area endures severe winter weather, make sure the water level is either comfortably above or comfortably below the level of the light. Otherwise, pressure from ice could crack the light’s glass lens.

For attached lights, unscrew the housing as you would do when you replace a bulb. Tie a weighted container to sink the light below the freezing line.

Above ground and on-ground lights should be removed and stored. Plug the opening in the pool wall with a rubber expansion plug.

Should I acid wash my DE pool filter before closing?

DE stands for diatomaceous earth. DE filters are an effective alternative to standard sand and cartridge pool filters. It is important to clean all types of pool filters, but the care process for them is not the same. DE filters benefit from a 24 hour soak in filter cleaning solution or diluted muriatic acid. Pool filter degreasers and alkaline based filter cleaners also will do a good job. Remember, acid is corrosive. Acid washing your filter more than once a year could damage it and shorten its life.

The cleaning process for other types of pool filters varies. Refer to the manufacturer’s instructions or contact a professional pool cleaning service for expert advice.

Should I add antifreeze to my pool when closing? The purpose of pool antifreeze is to prevent damage in the underground water lines that circulate your pool water. Above ground pools do not need swimming pool antifreeze.

Antifreeze is optional for inground pools. As part of your pool closing routine, use an air compressor to blow the water out of your lines. If done properly, you shouldn’t need to use antifreeze. However, some people apply antifreeze as added insurance against cracked pipes.

Do I need any other special equipment to close my pool?

There are a few pieces of inexpensive pool winterizing equipment that can help prevent pool damage over the winter and ease the task of opening the pool again in the spring.

Protect your skimmer from damage caused by ice expansion inside the unit by inserting a winter expansion absorber inside the skimmer.

A winterizing pool pillow is also a good idea. This rests on the surface of the pool water, beneath your winter pool cover. Any ice that forms on the surface of your pool will expand against the pillow, not the sides of your pool.

Consider a cover siphon pump to drain out any water that collects on top of the pool liner so the liner doesn’t split under the strain of rain or snow.

If you’re a newer swimming pool owner, how to close a pool for winter can be a mystery. However, getting clear answers to your pool closing questions can help you tackle the job with confidence.

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