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Pool Chlorine: Liquid, Tablet, Shock - Your Ultimate Guide

Updated: Nov 26, 2023

Explore the depths of pool chlorine, an indispensable element for preserving the clarity and hygiene of your utopia. Found in various forms, the primary variant is liquid chlorine, also known as hypochlorous acid, widely available at local hardware or pool supply stores. This comprehensive guide delves into the distinct types of chlorine, shedding light on their unique properties and versatile applications. From liquid to tablet to shock, discover the essential insights to keep your pool pristine and inviting.


Unstabilized Liquid Chlorine: Hypochlorous Acid

Unstabilized Liquid Chlorine, specifically hypochlorous acid, is an efficient means of swiftly achieving high concentrations to eliminate bacteria. This form is valuable for algae control, eradicating organic contaminants (Organic TDS), and restoring water clarity.


Stabilized Tablet Chlorine: Trichlor and Dichlor Tablets

Stabilized Chlorine, represented by trichlor and dichlor in solid tablet forms, incorporates trichloroisocyanuric acid or dichloroisocyanurate. These compounds include cyanuric acid, stabilizing chlorine ions and shielding them from the detrimental effects of UV light.


Granular Shock: Unstabilized Chlorine in Granular Form

Another type of unstabilized chlorine is granular shock, which includes calcium hypochlorite, sodium dichlor, and potassium monopersulfate. Granular shock aims to destroy bacteria, combined chlorine, or algae lingering in your pool.


Chlorine Testing: Ensuring Water Quality

There are three types of testing for chlorine levels:

  1. Free Chlorine: The active chlorine working to keep the pool water clean.

  2. Combined Chlorine: Chlorine combined with ammonia, hindering sanitization and causing a chlorine-like smell.

  3. Total Chlorine: The sum of free chlorine and combined chlorine.

To determine combined chlorine levels, you can use the Breakpoint Chlorination calculation:

Total Chlorine (TC) – Free Chlorine (FC) = Combined Chlorine (CC)Total Chlorine (TC) – Free Chlorine (FC) = Combined Chlorine (CC)

For example, if TC is 2.6 ppm and FC is 1.7 ppm, CC would be 0.9 ppm.


Breakpoint Chlorination Calculation: A Practical Example

  1. Determine the amount of combined chlorine (CC).

  2. Calculate the Breakpoint Chlorination (BPC) amount (BPC = CC x 10).

  3. Determine the desired change amount (Desired change = BPC – FC).

For instance, if CC is 0.9 ppm, BPC is 9.0 ppm, and the desired change is 7.3 ppm.


Practical Application: Pool Shocking

A quick search reveals that 1 lb of calcium hypochlorite granular shock per 10,000 gallons provides 5-10 ppm of available chlorine. For an 18,000-gallon pool with a desired change of 7.3 ppm, calculations show the need for 1.32-2.63 lbs of granular shock.


Preventing Combined Chlorine: Potassium Monopersulfate

After shocking your pool, preventing combined chlorine is possible with a weekly dose of Potassium Monopersulfate. This non-chlorine oxidizer, when used weekly, reacts with contaminants, preventing CC formation. A recommended dose is 1 lb per 10,000 gallons.

Understanding these common products ensures your pool stays sanitized and sparkling clean. For those who prefer a hassle-free approach, consider our weekly/bi-weekly/monthly service plans. Let us take care of your pool, so you can enjoy your own Utopia. If you have any questions, feel free to reach out – we're here to help.


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