► Too Much Shock?

Hello, here are my current readings: Hardness: 500, Free Chlorine 10, Total Chlorine 10, pH 7.2, Alkalinity 80 and CYA 30.  The problem is that after I shocked my pool on Sunday night the Chlorine residual has not come down to below 10 yet.  My pool is 16x32 with a shallow end of 3' and a deep end of 7.5' and the deep end is cove shaped which means the walls are sloped.  According to my reading the calculation is: length x width x av. depth x 7.5 x 0.85 (for sloped walls).  So I calculated 17,136 gallons.  I am the new owner of the house with the pool and this is only the second week the pool has been open.  When I shocked (superchlorinated) my pool on Sunday night I thought I had a 20,000 gallon pool because that is what the previous owner told me.  However, as the measurements show above, the pool is closer to a 15,000 gallon pool.  The instructions on my chlorine bucket say to use 5oz per 5,000 gallons so I added 20 oz. of chlorine granules into the skimmer.  I also left the 2-3" chlorine tablets in the skimmer that are normally there.  It is important to note that I have one of those blower driven pool domes over the pool so the water never gets hit by direct sunlight.  However, I would expect that by Wednesday morning the chlorine level should have come down by now.  Even if I accidentally miscounted and put in one extra scoop to make it 25oz, should the chlorine levels still be that high?  Should I look into adding a chemical that will lower the chlorine level for me or should I just wait it out?  Thanks for your help.

Peter H., 5/7/2006

You neglected to tell me the type of granular chlorine, so I'll assume that it has about 60% available chlorine.  Based on the amount that you added, a reading of 10 PPM is not unexpected.  The problem isn't that you added an extra 5 ounces.  The problem is that you didn't even need 20 ounces.  The 5 ounce/5,000 gallons dose is more than a normal maintenance dose.  In your case, the pool did not require a major shock treatment.  The fact that the Free Chlorine and Total Chlorine readings are the same seems to bear this out.  The amount that you added was more appropriate for a pool with visible algae.  By the time, you get this email, I suspect that the level will have dropped.  There is a chemical that can be used to quickly lower chlorine levels.  It is usually called Chlorine Neutralizer and many pool dealers carry the product.  Here's something to remember.  You can always add more - you can't take out.  The shock dosages on the chlorine packaging are guides:  some pools will require more or less based upon the actual conditions of the pool water.  I hope that I have been helpful  Enjoy the pool.

Sincerely.  Alan Schuster, 5/7/2006

Thanks for the info.  A number of places have been saying I should shock the pool once a week.  It would appear though that I should really only shock the pool when the combined chlorine gets above zero (to a measurable amount) or when there is an algae or other issue.  Does that seem right to you?  Thanks for the quick reply by the way.

Peter, 5/8/2006

It is uncommon to have the total and Free chlorine readings the same.  That implies zero combined chlorine and that is not the real world.  You should shock if the combined chlorine is above 1 -2 PPM, at first signs of algae or loss of water quality or anytime the Free Chlorine level bottoms out.  The absence of Free Chlorine can be the result of heavy bather usage, heavy rainfall or insufficient chlorine being added.  The practice of shocking a swimming pool once a week, does have a purpose:  it helps to prevent the growth of resistant microorganisms.  Enjoy the season.

Alan, 5/8/2006

► What is Non-Chlorine Shock?

What is potassium peroxymonosulfate (32.18%)?

Is it effective when used alone?

With Chlorine?

With Bromine?

Are there advantages?  Disadvantages?

Are there possible dangers when it is used in conjunction with any of the common pool chemicals?

Thanking you in advance.

Timothy Bowen, 8/2/2005

This is the chemical that is typically marketed as non-chlorine shock.  Like chlorine and bromine , it is an oxidizing agent that will destroy organic contamination and decompose dead algae and debris.  However, it is not considered a sanitizer and must be used with an approved sanitizer:  all except biguanide.  

If you add it alone, it will destroy contamination that might, otherwise have consumed some of the chlorine and/or shock.  It will act as a shock treatment.  If it is in excess, it will convert into chlorine, by reacting with any salt that might be present.

In a chlorine based pool, it will do exactly the same thing,  However, it may show up on the readings as a reduction in the combined chlorine and an increase in the free chlorine.  It will destroy odorous chlorines, by converting them into free chlorine.

In a bromine pool, it will work exactly the same as with chlorine, except that it will convert the bromides (present in the water) into bromine, if added in excess.

The advantages are that is very quick dissolving, gives the chlorine or bromine level a boost,  allows an automatic feeder a better opportunity to keep pace with the bather demand and contains no unwanted byproducts such as calcium or cyanuric acid.  Its cost is probably higher and there is the only serious disadvantage.  However, in most pools it will have positive advantages.

Never mix with any chemicals in the dry state.  Always add to the add.  The material is safe to use, as directed, in all types of pools and with all sanitizers.  It cannot be used in biguanide pools as it will destroy the biguanide polymer.  This is actually a preferred method of switching from biguanide to chlorine or bromine.  I hope that this information proves helpful.

Sincerely.  Alan Schuster 8/2/2005

► Too Much Stabilizer And Confused?

Hi Alan, I have a question about shock. I am using a feeder with 3" chlorinating tabs.  Last year my pool was way high in stabilizer and I could not get it lowered.  Everyone tells me different types of shock and I get confused.  Can you just tell me the name of a shock I can go buy and I don't have to worry about trying to figure out what is in each type.  Thanks.

Mary, 4/12/2005

A simple answer might not be best to solve your problem.  You need to read the labels!!!  Being that you are using trichlor tablets, do not use any shock product that contains sodium dichlor, as it will only speed up the increase in the stabilizer level.  You should use liquid chlorine, lithium hypochlorite or non-chlorine shock.  If your calcium hardness level is under 250 PPM, you could use calcium hypochlorite, as well.  Just monitor the calcium hardness level once a year and discontinue, if the hardness rises above 300 PPM.  The only way to lower the stabilizer level is to replace water.  High levels can tend to make chlorine less effective.  I hope that this information will enable you to make a better choice.

Sincerely.  Alan Schuster, 4/12/2005

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► Lithium Or Calcium Hypochlorite?

Alan, I am preparing to open a vinyl liner in ground pool installed last fall.  The pool has an in-line chlorinator and we use stabilized sticks. What is the difference between Lithium Shock and Calcium Hypochlorite Shock?  Would you recommend one over the other?  We don't know which one to use?  We live in Chicago and want to protect our pool investment.  Thanks.

Jim T., Chicago, IL, 3/7/2003

PS Your website is great, but I couldn't find the answer to my question.  Did I miss it?

You got me!  Well sort of!  There are references to the 2 products throughout various pages, but not all wrapped up, nice and neat, in a question like yours.  Lithium shock has 35% available chlorine, is completely soluble, dissolves quickly, contributes no problematic byproducts and will raise the pH.  Calcium hypochlorite has 65-70% available chlorine, is not completely soluble, dissolves slowly, contributes calcium hardness to the water and will raise the pH.  If you have calcium hardness readings above 200 PPM, the answer is simple - use lithium, liquid chlorine or non-chlorine shock.  If your calcium hardness is under 200 PPM, the choice is yours.  However, from the perspective of the vinyl liner, calcium hypochlorite is not best choice, especially, if it is added by broadcasting across the surface.  The important thing to remember is to use a quick dissolving shock and avoid allowing chlorine products to remain in contact with the liner.  While you might to able to use a dichlor product, I would not recommend it in your situation.  You are already using a stabilized chlorine and the use of dichlor will only accelerate the rise in the cyanuric acid level, forcing a partial water replacement.  I hope that the question has been answered.  I'll post it.

Sincerely.  Alan Schuster, 3/7/2004

► Lithium Or Monopersulfate Shock?

I have used lithium hypochlorite for years successfully.  I just read about potassium monopersulfate. Is this something new and is it a good choice for vinyl?  It seems to be much cheaper.

Cindy, 3/2/2004

Hardly new.  Misunderstood, perhaps?  The product has been around for about 25 years.  It is very quick dissolving and, as such, is well suited for use in vinyl liner pools.  But, so is lithium hypochlorite.  The difference is the potassium monopersulfate is not chlorine.  It is a powerful oxidizer and, after being added to pool water, it will destroy organic contamination and convert the irritating odorous forms of combined chlorine back into free chlorine.  If added in excess, it will convert the ordinary salt, present in the pool water, into free chlorine.  It can be used in conjunction with all various chlorine products. Never combine different products together!  Always add different products to the pool water and allow each to dissolve in turn.  I hope that I have explained the product. 

Sincerely.  Alan Schuster, 3/2/2004

► Needing Help?

Alan, I opened my pool this year and I have been battling the problem of algae. I have backwashed, vacuumed and nothing seem to work. When I vacuum there is a cloudy, dirty, slimy substance that appears on the top of the water. I have used a algaecide and a shock plus product. Please help me.

No Name, 6/13/2003

You most likely have algae.  Vacuuming alone will not get rid of the problem.  Algaecide alone will not get rid of the problem.  It may help kill some algae, but it will not solve the problem.  The key is adding enough shock treatment product to kill and decompose the algae.  Adding a single dose of pool shock may not be enough.  You may have to add repeated doses, until you have established a Free Chlorine reading that lasts through the night.  At that point there should be improvement in the water quality.  Adding a dose of a "Blue" Clarifier will help with the process. Filter continuously until the water is clear.  Thereafter, maintain normal operating conditions.  I hope that this information will prove helpful.

Sincerely.  Alan Schuster, 6/13/2003

► When Should I Shock My Pool?

I have been told differing things about when or how often I should shock my pool.  It is a 15,000 gallon above ground pool and is used by 2-3 kids all week and 2 adults on weekends.  What's your take?

Robert G., 3/21/2009

I have no doubt that you've heard differing recommendations.  The topic can be subjective.  I suggest that you shock the pool under the following circumstances:  a problem with visible algae seems to be developing, the Free Chlorine level has bottomed out,  heavy bather usage is depleting the Free Chlorine level, the Combined Chlorine (chloramines) level is too high, there is evidence of a slimy feeling on the underwater surfaces or there is a loss of water quality that is not attributable to the overall water balance.  In addition, you might consider shocking every Sunday Evening, as this is after the most active period of use.  This will help destroy resistant organisms and allow normal chlorine to satisfy the chlorine requirements.  Periods of heavy rainfall can bring contaminants and deplete the Free Chlorine level.  This is not black and white and how much pool shock treatment needs to be added will depend upon the particular situation.  The type of pool shock treatment used should be based upon the product best suited to the water chemistry and the sanitizer being used.  I hope that I have helped to clarify the subject.

Sincerely.  Alan Schuster, 3/21/2009

► How Much Shock Is Enough?

I think that I understand the reason why I might need to shock the pool occasionally.  My pool is about 9600 gallons and I find that, by following the label dosages, I do not always get the desired result.  I add 2 pounds at a time, but I seem to need another 2 pounds.  Is it just me or is the label wrong?

B. G., 7/12/2004

Adding 2 pounds at a time, to your size pool, seems appropriate.  The fact that you did not achieve the desired results or obtain a satisfactory Free Chlorine reading, indicates that the amount of algae (alive or dead), bather wastes, debris and combined chlorine was more than 2 pounds could destroy.  Consider the 2 pounds as an application guide and not as an amount that will always do the task.  Remember, you can always add more - you can't take out!  Add 2 pounds, allow a few hours to circulate and test for Free Chlorine.  If an adequate Free Chlorine level is found, hold off before adding more product.  Unless your pool looks like a swamp, adding 4 pounds at a time could raise the Free Chlorine level so high that you might not want to or be able to use the pool, until the Free Chlorine level drops.  And that is something you want to avoid!   I hope that I have been helpful.

Sincerely.  Alan Schuster, 7/12/2004

► No Reading?

Sincerely.  Alan Schuster, 5/2/2005

 

► I've Shocked and Shocked?

My pool developed algae because it was neglected for a week or two.  I brought a water sample into a local pool store and the only thing wrong was that there was no chlorine.  They gave me 4 pounds of shock and a bottle of algaecide.  I was told to add 2 pounds of shock and some algaecide.  The next day I was supposed to add the other two pounds.  I did all that and there is still no chlorine reading and the pool is cloudy.  There is still some algae left.  I went back and bought another two pounds and still no chlorine.  It has been 4 days now and the water is cloudy and there is no chlorine.  The algae seems to be gone.  I have backwashed the sand filter 2 or 3 times.  What should I try next?

Jim G., 7/14/2004

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