Guide to Winterizing Your Swimming Pool

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If you live in a cold climate, winterizing your pool is a necessary but sometimes bothersome requirement. Inground pools that are not properly winterized may end up with cracked pipes, broken hoses, and damaged walls. In order to winterize an in-ground pool, water quality needs to be adjusted, equipment cleaned and stored, the water level lowered, and a cover chosen and fitted.

Water Quality Parameters for Winterizing a Pool

Despite the fact that no one is going to be using the pool, water quality remains important during the winter. Because the goal of winterizing a pool is to prevent damage to the pool and its supporting structures, the water needs to be balanced and cleaned. If the water quality is not ideal, prolonged exposure to the water itself, when it is not being filtered and treated, could damage the pool.

The first step to creating ideal water chemistry is to balance the pool water to the following levels:

  • pH: 7.2-7.8
  • Alkalinity: 60-180 ppm
  • Calcium hardness: 150-1000 ppm

After reaching these levels, the next step is to shock the pool with a large quantity of sanitation chemicals. Chlorine is used for chlorine and bromine pools, and hydrogen peroxide for PHMB pools. When using chlorine, approximately 1-2 lbs per 10,000 gallons of pool water is needed.

It takes time for chlorine levels to fall, but it is necessary to wait because high levels of chlorine may react with the algaecide and render it useless. High chlorine levels may also damage pool covers. A range of 1.0-3.0 ppm is typically the goal before moving to the next step.

The use of a commercial algaecide is common but not mandated. Mechanically cleaning the pool will also help prevent the growth of unwanted organisms and remove waste. Make sure to clean all of the surfaces of the pool. Vacuum cleaners, skimmers, leaf-rake bags and other tools can be used. The goal is simply to remove as much material from the water and the surfaces of the pool as possible.

Preparing and Storing Pool Equipment

Most of the equipment will need to be cleaned and drained when winterizing a pool. A specialized blower or a wet/dry vacuum capable of the required low pressure is necessary to purge water from the pipes and hoses. High pressure can damage these, so make sure to use the proper equipment.

You should expect that someone will need to:

  • Clean and drain the filter
  • Drain the heater and pump
  • Purge all hoses and pipes
  • Turn off electrical power and make sure the circuit breaker is off
  • Turn off the gas and put out the pilot light on gas heaters
  • If severe weather is expected, remove motors for storage indoors

Pool equipment should be cleaned and allowed to dry thoroughly before storage. Once the hoses and pipes are purged, plugs will need to be placed on the pool end in order to prevent them from refilling with water. Some people use pool antifreeze in addition to blowing out the lines. If you choose to do this, use only pool antifreeze, not the kind intended for vehicles.

Types of Pool Covers

There are four basic types of pool covers:

  • Solid lightweight fabric
  • Spring-loaded mesh
  • Spring-loaded solid
  • Automatic and manual covers with tracks

Lightweight fabric covers are usually held in place with sandbags or anchors. Spring-loaded covers are typically anchored to the deck surrounding the pool. Tracked covers may be built into the sides of the pool or anchored on the deck.

Pool covers must be monitored for accumulation of snow, water, and debris. Solid covers must have drains or pumps to remove standing water because it presents a drowning hazard. All covers should be kept as clear as possible because excess weight can damage them.

Draining the Pool

How far you drain the pool depends on the material that it is made out of. Pool materials can be damaged by excess exposure to freezing air as well as by the expansion of ice if the top of the pool freezes over. Because of this, where the water line is located is important and depends on what the pool is made of.

In general, pools are drained to below the skimmer mouth and tile line. One to six inches is usually recommended. The exceptions are pools using mesh or automatic covers. Mesh-covered pools are typically drained 18-24 inches below the skimmer mouth, while automatic covered pools are usually not drained any lower than the skimmer mouth.

What You Need to Winterize Your Pool

You will need a few different types of equipment and supplies, many of which you probably have on hand already:

  • Water testing kit including tests for calcium hardness, pH, and alkalinity.
  • Chlorine or non-chlorine shock
  • Chemicals for adjusting water parameters if necessary
  • Leaf rake
  • Pool brush
  • Shop vac or air compressor for blowing out pipes and lines
  • Lubrication for o-rings
  • Algaecide (optional)
  • Chlorine or non-chlorine winter floater tablets
  • Air pillow for above-ground pools

Winterizing Non-Inground Pools

Above-Ground Pools

Most of the steps are the same for above-ground pools, except that the hoses and pipes will usually be disconnected entirely rather than purged and plugged. Sometimes air pillows are used between the water and the cover on above-ground pools in order to reduce water pressure on the walls. It is less common to use air pillows on inground pools, but some people do.

Salt Water Pools

A lot of the steps are the same for a saltwater pool. The major difference is the treatment of the salt cell and salt levels in the water. Some saltwater chlorine generators have a ‘winter’ setting. If yours does not, remove the salt cell and store it indoors. Use a powdered or liquid product to perform the last shock of the year because you do not want salt levels in the pool to be too high when you close it.

Opening Your Pool Again in the Spring

If you have properly winterized your pool, opening it should be relatively pain-free. There are a lot of steps, but most of them can be accomplished quickly. You may need help with a few of the steps, such as removing your pool cover.

  • Clean debris and water off of your pool cover
  • Remove pool cover carefully
  • Remove plugs from pool lines and pipes
  • Reinstall equipment such as ladders and step rails
  • Fill up the pool
  • Turn on the filter and make sure it is pulling water
  • Prime the filter (fill with water) if necessary
  • Clean leaves and debris out of the water with a leaf rake
  • Brush the sides and floor of the pool
  • Test your pool water with a professional-grade kit
  • Balance your water using the necessary chemicals for pH and alkalinity
  • Shock your pool with the appropriate shock (chlorine, bromine, etc.)
  • Run the filter for 24 hours and re-test

When should I open my pool?

A good rule of thumb is when the daytime water temperature is 70 degrees Fahrenheit or so. However, if you have very cold nights but warm days, watch out for freezing temperatures after opening the pool. If you accidentally open your pool before the last deep freeze of the year, keep your filter on all night because moving water freezes more slowly than still water.

Other Frequently Asked Questions

When should I winterize my pool?

The answer to this depends on where you live. Pools in areas that freeze should be winterized well before the first freeze. If water freezes in the pipes, they may crack and this can make for an expensive repair in the spring. For most people, as soon the pool is too cold to use (or falls below 65 degrees Fahrenheit) is a good time to winterize. If you live in an area that does not freeze often but you will not be using your pool during the winter, it can be winterized the same way and at the same time. In very warm areas, however, winterizing your pool may not be ideal because warm water requires more care and attention to avoid bacterial and algae growth than cold water does.

Should I use anti-freeze in the pipes?

The best thing to do with your pool is lower the water level enough so that you can completely drain the filtration system. This includes hoses, skimmers, chillers, and anything else attached to the pool. Blowing out the system with the proper tool will ensure that no water is left anywhere to freeze. Antifreeze can be used for additional insurance, or if you cannot blow out the pipes for some reason. However, it is not a magic bullet and it may not prevent all damage. If possible, it is better to blow out the pipes and seal them with the proper plugs.

Should I vacuum the pool before I winterize it?

Yes. You should clean your pool as thoroughly as possible before winterizing it, including by vacuuming. In addition to vacuuming, make sure to skim off leaves and debris on the surface, and then scrub the sides and floor with a pool cleaning brush. If possible, run the filter 24 hours a day for a few days before closing the pool.

What is the most important part of pool care in the winter?

Checking on the pool cover. All covers can fail if too much weight builds up on top of them, usually in the form of snow. Solid covers require a drainage system, including a pump, so that water sitting on top of them does not cause damage.


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