Granular vs. Liquid Shock

Water Chemistry
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In a vinyl liner in ground pool, is granular or liquid shock best? Is one pound of granular equal to one gallon of liquid? Can granular be added directly to the pool water or have to be mixed in a bucket before adding to the pool? Thanks in advance.

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Hi Are, those are good questions!  I’m going to keep this basic and talk about chlorine as the sanitizer/shock.  It really works the best and, frankly, most “shock” products are just concentrated chlorine to use after a pool party or rainstorm.  Di-Chlor, also known as sodium dichloro-s-triazinetrione, is typically recommended for vinyl liner pools as it dissolves rapidly and will not bleach or stain the liner.  It is also safer for fiberglass or painted surfaces for the same reason.

Granular or liquid? It is mostly a matter of personal preference.  I like liquid chlorine to shock my pool since it is cheap, does not have any additives, is ready to use (just pour it in), and I can use as much or as little as I need.  The granular shock is more shelf-stable than liquid chlorine (liquid chlorine loses some of the chlorine if it sits around too long), might contain additives (calcium, algaecide, or stabilizer), and tends to be more expensive.

Most of the one-pound bags of shock raise the chlorine level in a 10,000-gallon pool by 5-10 ppm; 64 ounces (1/2 gallon) of liquid chlorine (at 10% chlorine) would raise the chlorine level in a 10,000-gallon pool by 5 ppm.

We do recommend dissolving the granular shock products in a bucket before using them.  Some granules can bleach or damage a liner if they remain on the surface too long, so use your pool brush if you see any undissolved granules on the bottom of the pool to help them dissolve.

Whatever you use, do:

  • Dissolve granular chlorine shock in a bucket of water.
  • Add shock while the pump is running.
  • Pour dissolved shock or liquid chlorine directly into the pool.
  • Brush up any undissolved shock that settles on the floor of the pool.

And:

  • Do not mix granular chlorine shock or liquid chlorine with any other chemicals.
  • Do not pour shock into the skimmer. It could have a bad reaction with the chlorine in a tablet feeder.
  • Do not swim for 12-24 hours.
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As always, very helpful. Thanks alot