Types of Pool Shock: The Ultimate Guide

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I am sure that, even as a new pool owner, you already understand the importance of chlorine in pool sanitation.

But what about pool shock? Do you know what it is, why you need it, and the different types of pool shock? Moreover, which is the best pool shock for you?

In case, you are unclear about all these questions do not worry. Many new pool owners don’t have a good understanding of pool shock, so you are not alone.

More importantly, in this article, I will explain the three types of pool shock, with the pros and cons of each and a comparison table.

Choosing the best pool shock depends on your pool type, current water chemistry, type of algae infestation, and even how often your pool is used. 

By the end of this article, you’ll know exactly how to pick the right pool shock for your pool and keep your water sparkling clean and sanitized.

Key Takeaways

• Pool shock sanitizes and restores water clarity by eliminating bacteria and algae.
• Three types: Cal-Hypo, Dichlor, and Non-Chlorine Shock serve different needs.
• Use Cal-Hypo Shock for algae blooms and heavy contamination.
• Choose Dichlor Shock for stabilized chlorine and routine maintenance.
• Opt for Non-Chlorine Shock for fast results and gentle pool care.
• Factors like pool type, water pH, and bather load affect shock choice.
• Follow safety precautions to ensure effective and safe pool shocking.

What is Pool Shock? How Does it Work?

Pool shock is a concentrated dose of chlorine (or non-chlorine oxidizers), that is added to a swimming pool to rapidly increase the free chlorine from 2-4 ppm to 10-20 ppm.

This level of superchlorination overwhelms pathogens like algae, bacteria, and other contaminants.

Shocking the pool destroys harmful contaminants, breaks down organic waste, and eliminates unpleasant odors caused by chloramines (byproducts of chlorine reacting with organic matter). 

How Pool Shock Works

When you add pool shock, it serves multiple functions:

Pool shock sanitizes the water by killing harmful bacteria and viruses that can accumulate in spite of regular chlorination. The action is rapid (typically overnight!)

The pool shock also oxidizes and breaks down organic matter such as body oils, sunscreen, and leaves. These contaminants contribute to cloudy water and reduce the efficiency of your pool’s sanitizer.

Pool shock has the strength to eliminate all algae growth, whether full-blown or in the initial stage.

Shocking helps keep your pool free from green or slimy water by destroying algae growth and preventing regrowth, which can quickly ruin its aesthetic and safety.

Moreover, shocking reinvigorates your pool’s sanitizer. Over time, normal sanitizers like chlorine can lose their effectiveness due to the accumulation of chloramines (compounds formed when chlorine reacts with organic material).

Pool shock breaks apart these chloramines through a process known as breakpoint chlorination, leaving the water fresh, clean, and balanced.

Shocking your pool weekly during the season is a prudent and recommended pool maintenance guideline. You may also shock your pool after storms and heavy rains, pool parties, or any time the water looks or smells off. 

Types of Pool Shock

There are three main types of chemicals used for pool shock:

• Calcium Hypochlorite: A common granular form of chlorine that quickly dissolves and raises free chlorine levels.
• Sodium Dichlor: A stabilized form of chlorine that can be used in both indoor and outdoor pools.
• Potassium Monopersulfate: A non-chlorine shock that oxidizes contaminants without adding chlorine, often used for regular maintenance.

As we dive into the types of pool shock, you’ll learn which one is best suited for your specific needs.

Calcium Hypochlorite (Cal-Hypo) Shock

Calcium Hypochlorite, commonly known as Cal-Hypo Shock, is one of the most widely used types of pool shock. It’s a powerful chlorine-based treatment that works quickly to sanitize and oxidize pool water. 

Cal-Hypo is especially effective at killing bacteria and eradicating algae, making it a go-to choice for many pool owners.

Pros and Cons of Cal-Hypo Shock

Pros

• Highly effective: Cal-Hypo is excellent at eliminating algae, bacteria, and other contaminants.
• Fast action: Works quickly to restore water clarity and balance.
• Versatile: Suitable for most pool types, including traditional chlorine pools.
• Affordable: It’s often more budget-friendly than other types of shock.

Cons

• Increases calcium hardness: Over time, it can raise the calcium hardness levels in your pool, which may lead to scaling.
• Requires pre-dissolving: Granules need to be dissolved in water before adding to the pool to avoid bleaching the liner.
• Unstable in sunlight: The chlorine in Cal-Hypo breaks down quickly without proper stabilization.

Best Cal-Hypo Shock Products

When choosing a Cal-Hypo product, look for options that offer high purity and fast-dissolving properties. Here are some top picks:

• HTH Super Shock: Known for its high chlorine content (up to 70%), this product works rapidly to clear cloudy water and eliminate contaminants.
• Dry-Tec Pool Shock: A budget-friendly option that effectively sanitizes and oxidizes.
• In The Swim Pool Shock: A budget-friendly option that effectively sanitizes and oxidizes.

Cal-Hypo pool shock is ideal for regular maintenance and tackling sudden water quality issues.

Dichlor Shock

Dichlor Shock is a stabilized chlorine-based shock. Dichlor is short for “Dichloro-S-Triazinetrione”. Dichlor is manufactured by the chlorination of Cyanuric Acid (CYA). This is the reason Dichlor is stabilized chlorine.

Dichlor Shock, being stabilized, lasts longer in the pool water, even when exposed to the UV rays from the sun. This unique feature can be helpful in some cases.

Pros and Cons of Dichlor Shock

Pros

• Stabilized chlorine: The built-in cyanuric acid protects the chlorine, ensuring it lasts longer in sunny conditions.
• Fast dissolving: Dichlor shock dissolves quickly in water, leaving no residue.
• Gentle on pool surfaces: Ideal for pools with vinyl liners or delicate finishes.
• Doesn’t increase calcium hardness: Unlike Cal-Hypo shock, it won’t contribute to scaling.

Cons

• Adds cyanuric acid: While stabilizers are beneficial, too much cyanuric acid can reduce chlorine effectiveness over time.
• Not as strong as Cal-Hypo: It may take more product to handle heavy contamination or severe algae problems.

Best Dichlor Shock Products

Here are some highly recommended Dichlor shocks:

• Leslie’s Chlor Brite Pool Shock: Maintains clean, sanitized water and kills bacteria, while providing multi-use shocking and chlorination options.
• Clorox Pool&Spa Shock Xtra Blue: Offers stabilized chlorine with fast-dissolving granules, ideal for maintaining clarity.
• In The Swim Sodium Dichlor Shock: Powerful sanitizing powder that destroys bacteria, breaks down contaminants and kills algae.

Dichlor shock is particularly useful for regular maintenance, especially in outdoor pools where sunlight tends to deplete chlorine quickly.

However, you need to closely monitor the pool’s cyanuric acid levels to ensure they stay within the ideal range (30–50 ppm).

Non-Chlorine Shock

Non-chlorine shock, often made from potassium monopersulfate (MPS), is a chlorine-free oxidizer designed to break down organic contaminants in pool water. 

Unlike chlorine-based shocks, it doesn’t sanitize or kill bacteria, but it’s an excellent choice for reducing chloramines (the compounds that cause unpleasant odors) and improving water clarity.

Pros and Cons of Non-Chlorine Shock

Pros

• Gentle and safe: Doesn’t add chlorine to the pool, making it ideal for sensitive swimmers and frequent use.
• No waiting time: You can swim almost immediately after application.
• Effective at oxidizing organic matter: Removes oils, sweat, and other waste that cloud water and reduce sanitizer effectiveness.
• Works with all pool types: Suitable for saltwater, vinyl, fiberglass, and traditional pools.

Cons

• Doesn’t sanitize: It doesn’t kill algae or bacteria, so it’s often used alongside chlorine-based treatments.
• Less effective for heavy contamination: Not suitable for severe algae blooms or heavy bacteria contamination.

Best Non-Chlorine Shock Products

If you’re looking for reliable non-chlorine options, consider these products:

• Oxy-Brite Non-Chlorine Shock: Powerful non-chlorine shock with unique blue water-brightening crystals. Rids pool water of contaminants.
• Leslie’s Fresh ‘N Clear Shock: Non-chlorine shock provides all the oxidizing strength that you get with a chlorine shock, only without actually using chlorine.
• In The Swim Chlorine-Free Pool Shock: Eliminates organic contaminants and algae for clean, safe pool water.

Non-chlorine shock can be used as a supplement to chlorine shock but is not really an alternative.

Comparison Table of the 3 Types of Pool Shock

To help you choose the right pool shock for your needs, here’s a side-by-side comparison of Cal-Hypo Shock, Dichlor Shock, and Non-Chlorine Shock based on key features:

Feature	Cal-Hypo Shock	Dichlor Shock	Non-Chlorine Shock
Main Ingredient	Calcium Hypochlorite	Sodium Dichlor	Potassium Monopersulfate (MPS)
Chlorine Content	High	Moderate	None
Effectiveness on Algae	Excellent	Good	Not effective
Effectiveness on Bacteria	Excellent	Good	Not effective
UV Stability	None	High (contains stabilizer)	Not applicable
Impact on Calcium Hardness	Increases levels	No impact	No impact
Ideal for Cloudy Water	Excellent	Excellent	Good
Dissolving Time	Requires pre-dissolving	Dissolves quickly	Dissolves quickly
Waiting Time to Swim	8–24 hours	8–12 hours	15 minutes
Cost	Budget-friendly	Moderate	High
Best For	Killing algae and bacteria in chlorine pools	Routine maintenance in outdoor pools	Frequent maintenance with minimal downtime

Key Takeaways

• Use Cal-Hypo Shock for heavy contamination, such as algae blooms or green water.
• Choose Dichlor Shock for routine maintenance in outdoor pools where sunlight is a factor. Monitor CYA levels regularly.
• Opt for Non-Chlorine Shock if you prioritize fast turnaround times and reduced chemical exposure. It is also a great choice for spas and hot tubs.

Choosing the Right Pool Shock: Factors to Consider

Selecting the best pool shock for your needs depends on a host of factors, such as, pool type, current water conditions, how often you use it, etc. Below are the critical factors to consider, with explanations to help you make the right decision.

Pool Type (Saltwater vs. Chlorine)

The type of pool you have influences the choice of pool shock.

• Saltwater Pools: Use Non-Chlorine Shock or Dichlor Shock to avoid disrupting the delicate salt-to-chlorine conversion process. Chlorine-based shocks like Cal-Hypo can overwhelm the salt system.
• Traditional Chlorine Pools: These pools are more flexible and can use any type of shock. However, Cal-Hypo Shock is particularly effective for eliminating algae, bacteria, and organic contaminants.

Granule vs. Liquid vs. Tablet Shock

The form of shock impacts ease of use and effectiveness.

• Granules: Are the most popular as they are easy to dissolve in a bucket of water and then pour in the deep end of the pool.
• Liquid: Are even more easy to distribute as they don’t require any pre-mixing. However, they tend to be less concentrated than granules.
• Tablets: Convenient for slow, controlled release for sanitation. However, tablets are not ideal for shocking a pool.

Stabilized vs. Unstabilized Shock

A stabilized shock like Dichlor contains cyanuric acid, which protects chlorine from sunlight. On the other hand, unstabilized shock like Cal Hypo does not have any cyanuric acid and will deplete fast once the sun comes out.

• Unstabilized Shock (Cal-Hypo): This is a better option as you can shock the pool in the evening. The shock works on the pathogens throughout the night. However, the chlorine spike depletes in the morning so that the free chlorine drops to below 5 ppm, making the pool safe to swim.
• Stabilized Shock (Dichlor): This is a good option if you do not plan to swim for a day or two. The chlorine spike gets more time to deal with the pathogens. However, use this option only if the cyanuric acid in your pool is not above recommended levels.

Chlorine Requirement

Consider how much of a chlorine spike you are looking for.

• Use a chlorine-heavy option like Cal-Hypo Shock if your pool has an algae infestation or got hit by a heavy downpour.
• Dichlor Shock works well in pools where cyanuric acid levels are well managed and you want to avoid scaling.
• Choose Non-Chlorine Shock for dealing primarily with organic contaminants. This is a great option after a pool party!

Pool pH Level

Balanced pH levels (7.2–7.6) ensure shock treatments work effectively.

• Shocks like Cal-Hypo can temporarily raise pH levels, so adjust pH before and after use if necessary.

Wait Time Before Swimming

How quickly you can swim after shocking is another key consideration.

• Non-Chlorine Shock: Allows swimming in as little as 15 minutes, making it ideal for quick turnarounds.
• Cal-Hypo Shock: If you shock the pool after sunset, run the pool pump throughout the night, chances are that the pool chlorine level will be at a safe level for swimming in the afternoon.
• Dichlor Shock: This will take longer as the cyanuric acid in Dichlor will not let the free chlorine degrade under the UV radiation fast enough. Test the chlorine level before diving in, but expect to wait for 24-48 hours before your pool is ready.

Type of Algae Growth

The type and severity of algae in your pool will dictate the best shock treatment. Honestly, Cal Hypo Shock is the only weapon in your arsenal to combat algae growth.

Moreover, you will have to use higher doses for different types of algae growth.

Pool Usage (Frequency and Swimmer Load)

You can choose the pool shock based on your pool usage pattern.

• Daily Usage: If you want to use your pool every day of the week then a Non-Chlorine Shock has to be your choice, as there need not be any wait time.
• Weekend Usage: Often families are unable to use the pool during weekdays but have a heavy usage during the weekend. In this case it is best to shock the pool on Sunday night with Cal-Hypo Shock or Dichlor Shock.

Budget

Cost is always a consideration when maintaining a pool.

• Cal-Hypo Shock: The most cost-effective option, especially for large pools with heavy contamination.
• Dichlor Shock: Moderately priced and suited for routine maintenance.
• Non-Chlorine Shock: The most expensive option but offers convenience and quick results. No wonder it is highly recommended for spas and hot tubs.

Safety Precautions When Using Pool Shock

Handling pool shock requires care, as the chemicals involved can be hazardous if mishandled.

Follow these safety guidelines to ensure a safe and effective shock treatment process:

1. Wear Protective Gear

Always wear gloves, safety goggles, and protective clothing when handling pool shock. Pool shock can irritate or damage your skin, eyes, and respiratory system.

2. Read the Manufacturer’s Instructions

Each type of pool shock comes with specific usage directions. Follow the recommended dosage and application method to avoid over-shocking or under-shocking your pool.

3. Handle Chemicals Carefully

• Never mix different types of shock or other chemicals, as this can cause dangerous reactions.
• Always add chemicals to water, not the other way around, to prevent splashing and violent reactions.

4. Keep Products Dry and Stored Safely

Store pool shock in a cool, dry place away from direct sunlight, moisture, and other chemicals. Wetting shock granules or tablets can result in fire or toxic fumes.

5. Ventilate When Adding Shock

When applying shock, especially Cal-Hypo Shock, ensure proper ventilation to avoid inhaling fumes. If possible, shock the pool in the evening to minimize exposure to sunlight and evaporation.

6. Allow Time Before Swimming

• For Cal-Hypo or Dichlor Shock, wait at least 8–24 hours or until chlorine levels drop below 5 ppm.
• For Non-Chlorine Shock, you can usually swim within 15 minutes. Test the water to confirm it’s safe.

7. Test Water Chemistry After Shocking

After shocking, test the pool’s chlorine levels, pH levels, and total alkalinity to ensure balance before resuming regular pool use.

8. Keep Out of Reach of Children and Pets

Store all pool shock products securely to prevent accidental ingestion or exposure.

Frequently Asked Questions (FAQs)

Thank you very much for reading the post. I do hope you found it informative and helpful.