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Non Chlorine Shock vs Chlorine Shock: What’s Best for Your Pool or Spa?

non chlorine shock vs chlorine shock
Written by David Stern
Last Update: August 10, 2023

The answer can go in many ways as there are many options available with their own sets of advantages and disadvantages. But here’s a quick way to make a good decision!

If your pool, spa, or hot tub has bacterial or algae contamination then it is good to go for chlorine-based shocks since they work both as a sanitizer and an oxidizer. You can use calcium hypochlorite as it is the cheapest and most balanced chlorine shock on the market.

Sometimes you may have to choose both because you may need to oxidize separately for high-traffic pools.

If you need a quick solution or in the case of hot water, there is no alternative other than non-chlorine shocks as chlorine shocks need much more waiting time and they can’t be used in warm water.

Note: Don’t mix dichlor/trichlor with calcium hypochlorite and bromine-based shocks with chlorine-based shocks because they can cause a dangerous chemical reaction.

What’s a non-chlorine shock?

Often called MPS (monopersulfate), non-chlorine shocks are odorless agents that contain oxygen combined with sodium or potassium salt. Here MPS or monopersulfate is short for potassium peroxymonopersulfate.

These potassium-based shocks are commonly used to perform oxidation (breaking down the organics and oils in water), which is different from sanitization (killing of bacteria) that chlorinated shocks do.

What’s a non-chlorine shock

They are relatively safer than chlorine shocks since they don’t contain chlorine. You can quickly remove dead skin, sweat, dirt, and sunscreen in water within around 15 minutes.

If your pool or spa water is slightly polluted without any presence of algae in it, non-chlorine shocks will suit you best.

What’s a chlorine shock?

What’s a chlorine shock

Chlorine shocks work both as a sanitizer and an oxidizer with the main function of killing bacteria and algae.

There are many different types of chlorine shocks with the most common one being calcium hypochlorite. Others are dichlor, trichlor, sodium hypochlorite, and lithium hypochlorite.

Non-chlorine Shock vs Chlorine Shock: How They Differ

Comparing points Non-chlorine shock Chlorine shock
Method of action Only oxidization Sanitation and oxidation
Works better on Dead skin, perspiration, dirt, and sunscreen Bacteria and algae
Purpose To decompose unwanted organic materials To disinfect water killing microorganisms
Waiting time About 15 minutes  12 – 24 hours on average
Stabilizer (cyanuric acid) Doesn’t produce any Some varieties produce, some don’t
Odor No odor Strong odor of chlorine
Bleaches Doesn’t bleach delicate materials Bleaches clothes and soft surface areas
pH level Has lower pH pH level varies according to type
Price Costs 10% more than chlorine shock Cheaper except lithium hypo
UV light No effect Heavily affected
Removal action Chloramines and ammonia Chloramines and ammonia
Temperature Can be used in any temperature Can’t be used in hot or warm water
Residues formation Doesn’t produce combined chlorine Produces combined chlorine
Best for Slightly polluted water Heavily polluted water
Varieties Fewer varieties available More varieties available
Forms Tablet and powder Liquid, tablet, granular, and powder
Timing Can be used anytime Only when the sun is down
Shelf life Comparatively shorter shelf life 3-5 years if properly stored
Calcium level Does not increase Some varieties increase
Time of action Quick Quick except tablet forms
Overdosing management Medium Easy
Needed quantity Comparatively less Varies with types
Suitable for All pool types Indoor pools only
Side effects No significant side effects May cause skin irritation and red eyes
Mixing problem Can freely use with any pool chemicals Some varieties can’t be mixed
Using facility Easy to use Depends on types

Different types of non-chlorine shocks

1. Sodium monopersulfate


  • Odorless
  • Ultraviolet rays don’t affect it
  • Doesn’t burn eyes
  • Doesn’t produce chloramines
  • Doesn’t bleach swimwear
  • Doesn’t affect water temperature
  • Doesn’t cause itching on the skin


  • Sterilization doesn’t happen
  • Doesn’t kill bacteria and algae
  • Can’t remove chloramines
  • Lowers the pH level, which reduces the effectiveness of other chemicals

2. Potassium monopersulfate


  • Only 15 minutes are needed to oxidize the contamination
  • Improves chlorine efficiency if applied weekly
  • Saves money since you don’t need to use much to get effective results (Only 2 lbs are needed for 10,000 gallons of water)
  • Enhances water clarity
  • Doesn’t increase calcium and chlorine levels
  • Helps in enzyme treatments
  • Doesn’t raise cyanuric acid levels
  • Applicable in all types of pools
  • Removes ammonia and chloramines
  • Non-sensitive to sunlight that makes it possible to use any time
  • Can be added directly to the pool water
  • Odor-free
  • Doesn’t cause irritation
  • Water temperature doesn’t affect it and Can be used in both normal (78°F–82°F) and hot water
  • Can be used with both bromine and chlorine


  • Costs about 10% more than chlorine shocks
  • Works only as an oxidizer and doesn’t kill bacteria or help control algae growth
  • The alkalinity of the pool maybe reduced because it‘s low 2.3 pH level
  • Increases the total dissolved solids (TDS) level
  • Can give a false reading of combined and total chlorine levels as potassium reacts with monopersulfate

Different types of chlorine shocks

2. Calcium Hypochlorite (Cal-Hypo)


  • The cheapest chlorine-based pool shock out there
  • Kills bacteria and stops algae growth
  • Does oxidation too, along with sanitization
  • Fast-acting shock
  • Quick-release and fast acting
  • Removes ammonia and chloramine
  • Can be found in different strengths
  • Only about 1 lb is needed for 10,000 – 15,000 gallons of water
  • Raises free chlorine without increasing cyanuric acid
  • Easy to find as it is the most common type of shock


  • High pH level
  • Susceptible to UV rays
  • Can’t be used any time you want, especially when the sun is bright
  • Increases the calcium level of water
  • Longer waiting time to work; i.e., 18-24 hours
  • Bleaches swimwear, dark clothing, and hair
  • Leaves combined chlorine as residues
  • May burn the eyes and cause itchy skin
  • Can’t be used in a spa or hot tub as calcium hypochlorite will be burned by the warm water

2. Sodium hypochlorite (Liquide chlorine)


  • Relatively inexpensive
  • Only 1 gallon is sufficient for 10,000 gallons of water
  • Easy to manage if you over shock the pool because the sun burns off the chlorine over time
  • Fast action
  • Easy to use as you can apply it directly onto the water
  • Perfect for high-traffic or commercial pools since it can be added in bulk
  • Sodium hypochlorite is strongly alkaline in nature (pH – 13)


  • Highest pH level among different types of chlorine shocks
  • Bleaches out vinyl liners, paint, and sensitive or soft surfaces
  • Long waiting time; i.e., 24 hours
  • Need to add more acid to neutralize the pH level

3. Lithium hypochlorite


  • Doesn’t raise the calcium level of the pool
  • Quickly dissolves in water
  • The pH level remains unchanged
  • Doesn’t burn soft surfaces like vinyl liners or fiberglasses


  • Most expensive of all pool shock options
  • Doesn’t produce stabilizer like CYA (cyanuric acid), which protects chlorine from UV light
  • Has a low FAC (Free Available Chlorine) level (28-30%) compared to some other chlorine shocks, which means you have to use a large amount to get good results

4. Dichlor and trichlor


  • Suitable for pools with high levels of algae
  • Not sensitive to UV rays
  • Easy to use as they come in tablet forms
  • Stabilizes chlorine as it contains cyanuric acid, which protects the chlorine from sunlight
  • Self-maintaining as the tablet mixes slowly into the water
  • Has the strongest chlorine concentration among the different chlorine-based shocks
  • Long shelf life


  • May raise cyanuric acid levels quickly because 1 ppm of chlorine produces 0.6 ppm of acid
  • Can rust and stain your pool
  • May increase the acidity of the pool (pH – 3)
  • Slow in action as the tablets dissolve slowly
  • Can’t be used with calcium hypochlorite or there will be a dangerous chemical reaction
  • Has stabilizers (cyanuric acid) in high levels

About the author

David Stern

Despite a humble beginning at a childcare facility, David sored to success due to his inextinguishable desire for learning and a rare self-motivational disposition. The day he received his appointment letter from LANE ENGINEERING CONSULTING, P.C. was the happiest day of his life. He was trained in plumbing and fire protection systems. The firm taught him the fundamentals of waterproofing, facade restoration, mechanical and structural plumbing. His profound and innovative plumbing knowledge sets our research guidelines. He’s currently working on his new book titled “Plumbing Essentials.”

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