How to Open a Swimming Pool

Spring Openings

Based on 10,000 gallons (37,855 Liters)

Opening A Swimming Pool PDF



Assuming your swimming pool was winterized proactively (with the LSI in mind to prevent surface or finish damages), spring opening should be a simple procedure. Pools that were closed in the fall using the Orenda Winterization Procedure should not have any calcite crystals, winter dust, or other surface damage. The water should also be relatively clean and clear, provided the pool is opened before the water is 65ºF (18.3ºC) or warmer. 

The water chemistry priorities in this procedure are to balance the LSI of the water (Pillar 1), chlorinate, and to purge the pool of phosphates (Pillar 3) and non-living organics (Pillar 2). Here is how to open a swimming pool.

Related: How to Implement the Orenda Program

You will need:

  • Work gloves, a good attitude, and a badass theme song as you walk into the backyard with confidence
  • A test kit and acid demand test
  • A thermometer
  • Non-stabilized chlorine (liquid sodium hypochlorite or cal hypo shock)
  • PR-10,000 Phosphate Remover
  • CV-600 or CV-700 Enzyme
  • (Optional if necessary) SC-1000 Scale & Metal Control
  • Calcium chloride and/or sodium bicarbonate
  • Muriatic acid with measuring cup and safety glasses and gloves
  • A clean bucket to dilute and pre-dissolve chemicals

Spring Opening (after pollen season, if possible)

This procedure begins after you do the obvious physical opening practices, like uncovering the pool, raising the water level if needed, turning on the circulation and filtration system, as well as vacuuming and/or brushing. Once the pool is circulating and filtering properly, proceed with the following steps:
  1. Test water chemistry, and input readings into the Orenda calculator.
    • If your water temperature is 60ºF (15.5ºC) or colder, warm up the water sample before testing. Many test kits do not give accurate water chemistry readings for cold water.
  2. Adjust the water chemistry to balance the LSI. Usually this means raising the alkalinity or calcium hardness due to dilution over the winter (rain and snow contain zero calcium hardness).
  3. Chlorinate the pool with a non-stabilized chlorine (liquid sodium hypochlorite or cal hypo shock). Raise the chlorine to 5-10 ppm, depending on the condition of the water.
  4. Purge the pool with 8 fl.oz. of PR-10,000 phosphate remover around the perimeter of the pool.
  5. If the water temperature is 65ºF (18.3ºC) or warmer, also purge with One quart (32 fl.oz.) of CV-600 or CV-700 enzymes directly into the skimmer, gutter, or around perimeter of the pool.
    • (Optional if necessary) One quart (32 fl.oz.) of SC-1000 directly into the skimmer. This purge dose can be divided up over multiple visits, as it will wipe out free chlorine.
      • SC-1000 is only necessary if the pool is on well water, has a salt chlorine generator, calcium issues from the winter (like calcite crystals, winter dust, or what some might consider "scale"), or high metal content in the tap water. If your pool does not meet these descriptions, SC-1000 is not necessary.

Follow up visits

  1. If the water temperature was colder than 65ºF (18.3ºC) on opening day, purge the pool with CV-600/700 enzymes once the water warms up above that threshold.
  2. Maintain LSI balance every week. You can use the Orenda App for specific dosing instructions.
  3. Brush pool, clean, vacuum, etc. as you normally would.

Additional Notes

If the pool is green, brown, or just generally nasty, prioritize getting the filtration system running, shocking with chlorine and adding PR-10,000 phosphate remover. Once the water clears up (hopefully by your next visit), proceed with physically cleaning the pool and moving forward with the procedure, such as balancing the LSI, and adding enzymes.


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