How to Winterize a Gunite Swimming Pool


Gunite pools have walls that are made of a mixture of sand and cement that form a hard surface which is then coated with plaster. Winterizing, or closing, a gunite pool prevents damages cold weather can cause in the winter months, ultimately saving you time and money. Winterize your pool in the fall before temperatures begin to drop. If you live in an area where temperatures never reach freezing, this process is not necessary. Instead you can reduce the amount of time you run your pool each day.

Things You'll Need

  • Pool test kit
  • Chlorine
  • PH Up
  • PH Down
  • Shock
  • Algaecide
  • Submersible pump
  • Air compressor or shop vacuum
  • Bathtub plugs
  • Pool cover
  • Test your pool water to check that the chlorine, acid and alkaline levels are within range. Follow the instructions that come with the test kit. Take a sample of your pool water to your local pool supply store for testing if you prefer not to complete the test yourself. Add chlorine if needed and use pH Up and Down to adjust the pH level of your pool. Chlorine levels should read about 2 parts per million while pH should be between 7.2 and 7.6.

  • Apply shock to your running pool and continue to run the pump for six to eight hours. Use the shock intended for gunite pools.

  • Treat your pool with algaecide. It is important that the algaecide be added before you blow out the lines. This will ensure that algae does not grow while the pool is closed.

  • Backwash your pool filter for three minutes to ensure proper removal of debris. If you have a diatomaceous earth, or DE, filter, backwash until you no longer see DE in the filter eyeglass.

  • Turn off your pump. Pull or unscrew the filter plug near the bottom of the filter. Allow all of the water to drain out. Replace the plug.

  • Rent a submersible pump from your local home repair store. Drain your pool with the pump until the water level is below the skimmers. If your gunite pool is tiled on the top, reduce the water until the level is below the tile and the skimmers to prevent cracking.

  • Place a shop vac or an air compressor hose into your skimmer return line. Blow out the line until there is no more water running into the pool from the jets. Repeat this step for every skimmer return line in the pool. If you use a shop vac, you will need to put it into reverse first. You can rent a compressor from your local home repair store. Ask the sales clerk for specific directions on safety and use.

  • Purchase bathtub plugs from your local supply store. Make sure they will fit properly into your skimmer return lines. Cover the holes with the plugs so that water cannot get into the lines during the winter months.

  • Take detachable ladders, slides, filter baskets and toys out of your pool and store them for the winter.

  • Cover your pool with a tarp or pool cover after you winterize. This will reduce the amount of organic matter that collects in your pool and causes stains.

Tips & Warnings

  • Pick up shock and algaecide from your local pool supply store. Read the special winterizing instructions on the bottles to determine the amount you will need to apply for the winter.
  • Never shock your pool and treat it with algaecide at the same time. Doing so causes the chlorine to break down faster.

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  • Photo Credit Pool image by crossgolfing from
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