The Post-Fill Orenda Startup™

The Post-fill Orenda Startup™ (Plan B)

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

SAFETY NOTE: Pre-dissolve all dry chemicals in water prior to adding to the pool. Never throw dry chemicals directly into the pool, and never allow chemicals to sit directly on a pool surface.


In a perfect world, a pool startup is done in the proper sequence of events, with the startup technician turning on the fill water. But many times, the startup technician is not able to be there (or is unaware the pool is filling). So if you want to do the Orenda Startup, but for whatever reason you get there when the pool is partially full or completely full, this procedure is for you. This is plan B, aka "the switcheroo." It's not ideal but should stop further loss of calcium hydroxide and help you get the startup back on track.

The objective here is to simultaneously bring the pH down while raising the calcium hardness with pre-dissolved, chelated calcium. Doing one without the other leads to more issues. Either calcium will precipitate as dust or scale (due to high pH), or the water will etch plaster and pull out more calcium hydroxide (due to lowering the pH and making the water even less saturated with calcium). In either case, you're back at square one.

Related Procedure: The Orenda Startup™ Procedure (step-by-step)

You will need:

  • Test kit and water thermometer
  • A plastic tarp
  • Liquid and Dry measuring cups
  • Protective gear (glasses, rubber gloves)
  • The Orenda App
  • At least one clean bucket (or the Orenda Startup Barrel™)
  • Calcium Chloride
  • Sodium Bicarbonate
  • Muriatic Acid
  • Orenda SC-1000 (32 fl.oz./10,000 gallons, rounded up to nearest 10,000 gallons)
  • Orenda CV-600 (32 fl.oz./10,000 gallons)
  • Stirring stick


  1. Bring equipment to the job site. Lay down the plastic tarp near the edge of the pool to put your buckets and/or Orenda Startup Barrel™ down. Fill the buckets about halfway with pool water. If using the barrel, use a bucket to scoop pool water and fill the barrel about halfway full of water.
  2. Test the pool chemistry and input the results into the Orenda LSI calculator and adjust the parameters on the right side of the calculator to achieve the following three targets:
    1. LSI value of  0.20 to 0.29  (ideal)
    2. Target minimum of 300 ppm calcium hardness.
    3. Minimum combined Calcium + Total Alkalinity level of 400 ppm. 
  3. The Orenda App will prescribe the amount of calcium chloride and acid needed for the procedure.

You are now set up and ready to mix and pre-dissolve chemicals.


  1. Pre-dissolve the prescribed amount of calcium chloride in the Orenda Startup Barrel™ or 5-gallon buckets.
    • Add half a quart (16 fl.oz.) to a full quart (32 fl.oz.) of the SC-1000 purge dose into the barrel. If using buckets, aim for no more than 15 pounds of calcium chloride per 5-gal bucket, and add about two tablespoons of SC-1000 per bucket.  The rest of the purge dose goes directly into the pool.
    • In the bucket(s) or barrel, add 12 fl.oz. of 31.45% muriatic acid per quart (32 fl.oz.) of SC-1000 to neutralize its pH.
  2. Stir the calcium solution until completely dissolved. The water should be clear enough to see the bottom of the barrel or bucket and cooled down prior to proceeding.
  3. Calculate how much acid is needed to bring the pH down to about 7.8 in the pool. Divide this acid up amongst the buckets, or into the barrel with everything else.
  4. Once all is blended together, pour the buckets around the perimeter of the pool. If using the Orenda startup barrel, use channel locks to open the drain valve at the bottom and dump the barrel into the pool at once.
  5. Add the purge dose of enzymes CV-600 in the pool or skimmer. 
  6. Brush, brush, and brush some more.

Filling the Spa (if applicable)

  1. Do this process in a single bucket with very diluted acid, a tablespoon of SC-1000, and a small amount of calcium chloride. Stir until completely dissolved, then add to the spa and brush thoroughly.

Day 2 and beyond

  1. Follow our normal startup procedure from here on out, maintaining LSI balance.
  2. Do not use wheeled vacuum cleaners or add salt until at least 28-30 days.


This process aims to 'stop the bleeding' of calcium hydroxide and get your startup chemistry back on track. By arriving after the pool is full, the initial loss of calcium hydroxide has already occurred.  It is a mistake to simply lower the pH and keep brushing, because the water will just seek LSI balance again, by eating more calcium from your plaster.  Saturate the water's need for calcium hardness while simultaneously lowering the pH so it stays dissolved. That's what this procedure is all about. We replace the high pH's LSI value with dissolved calcium, hence our highly scientific nickname for this process: "the switcheroo."

Additional information and Disclaimer

The Orenda Startup Barrel™ should only be operated by a pool industry professional. These are Orenda Technologies' recommendations but we are not liable for the use of calcium chloride and/or the build-out or purchase of fill tanks.

Calcium chloride in water gets extremely hot and can cause burns. Appropriate eye and skin protection should be worn while handling chemicals. Use at your own risk and liability.

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