Pool Shock | Liquid Pool Shock Or Granular? If You Had To Choose

Swimming pools need to be “shocked” once a week or every two weeks.  More frequent shocking is needed if the pool is being heavily used, after extended periods of sunshine, heavy rainfall, if swimmers complain of odors or irritation, the water becomes murky in appearance, visible algae seems to be developing or whenever the free chlorine level bottoms out.

Pool shock is a form of super-chlorination that has the effect of removing combined chlorine (i.e. chlorine that has combined with contaminants in the water as part of a normal sanitation process) and returning active chlorine levels back to safe levels.

Most pool owners use a granular chlorine shock treatment with calcium hypochlorite as the active ingredient.  The critical data point to look out for when comparing products is the percentage of available chlorine.  A 65% level of calcium hypochorite or available chlorine is the standard.  Any less and the product may not be effective.  The manufacturer may claim that you can swim shortly after using (say) a 30% available shock treatment for example, but your objective of returning your pool to a clean and sanitized condition may not be achieved.  More concentrated versions of pool shock with 75% calcium hypochlorite are also available, often referred to as super plus or super shock treatments. See more on the different types of chlorine in our article on pool chemicals.

But what about liquid pool shock?

Liquid pool shock has pros and cons and your decision will depend according to your specific needs.  As liquid pool shock is quick dissolving and you wont run the risk of damaging (bleaching primarily) the pool liner or any other surfaces.  If you have a vinyl swimming pool, liquid pool shock may be the safer option and is sometimes referred to as a vinyl pool shock.  Remember though that there are some granular shock treatments that are safe to use in vinyl pools.  When it comes to cost, granular shock tends to be a more cost-effective choice.  When considering which product to purchase, do a side by side comparison comparing the available chlorine levels.

We have seen some liquid pool chlorine shock treatments with as little as 10% available chlorine.  Our advice: steer clear of these, however easy they may be to add to the pool.

Tags: liquid pool chlorine