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What Kind Of Chlorine To Shock Saltwater Pool?

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I have a 15,000 gallon gunite inground saltwater pool and in the past I've used regular old chlorine bleach to shock my pool - and it worked really well, but now it's peak swimming season and the child who swims in my pool every day is very sensitive to chlorine so I want to over-do it, but at the same time I had an algae bloom!

I checked my water and the chlorine level is very low, but I had to add soda ash first. Now I don't know what kind of chlorine to add to kill the algae and yet be safe enough to swim in.

At my local Leslie's they always sell me some special kind of shock because I have a saltwater pool. It's expensive and I'd need a lot of it. Do I need to buy that or - I went to Costco and they are selling Aqua Chem Shock Plus, which is Sodium dichloro-s-triazinetrione. I didn't buy that because it's granular and I'm not sure if that will harm my pool or my swimmer.

What do the experts recommend?

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Use bleach. Chlorine is chlorine and sodium hypochlorite (bleach) has the fewest side effects and is also what your SWCG is producing in your pool anyway. Also, if you have algae with a SWCG then either your CYA is low and the chlorine is burning off or your FC is too low for your CYA level. If you could post a full set of test results not done with strips we can help.

If you have algae then yo are going to have to raise the FC high enough to kill it. Period. Depending on your current CYA level it might be ok for swimming or not.

Post the test results.

How is the child 'sensitive' to chlorine? Most people have problem with chloramines (from improperly maintained water) rather than chlorine. Also, you might want to google 'bleach bath for eczema'. It is a pediatric treatment for eczema that involves a bath in a very high chlorine (bleach) level, around 50 ppm. There is no documented medical evidence of chlorine sensitivity, btw.

The dichlor from costco will cause your CYA levels to rise quickly. If you don't need to add CYA to the pool then you don't want to use that. The 'special shock" from leslies is just marketing hype. There is no special form of chlorine known as shock. Shock means rasiing the FC level high enough to either kill algae or break down chloriamines in the water and it usually means raising the FC high enough that you don't want to swim until the level drops a bit.

Chlorine is not going to harm your swimmer. Not testing your water and maintaining it properly might. If you have algae then you are not maintaining it properly, Do you have your own test kit? I know that has been suggested to you several times in the past,.

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Ok - I'll get bleach. Thanks! - oh and yes I do have a Taylor test kit. We're having a heat wave and the algae came on fast. The chems have been really good for a long time - they went south fast. I will test my chems after work today and post them here.

The child who swims in my pool is fine in my saltwater pool for hours, but if she goes to a public pool her eyelids swell, turn red, and her eyes burn. Everyone else swimming with her will feel fine but she will be in pain and want to leave.

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Ok - I'll get bleach. Thanks! - oh and yes I do have a Taylor test kit. We're having a heat wave and the algae came on fast. The chems have been really good for a long time - they went south fast. I will test my chems after work today and post them here.

The child who swims in my pool is fine in my saltwater pool for hours, but if she goes to a public pool her eyelids swell, turn red, and her eyes burn. Everyone else swimming with her will feel fine but she will be in pain and want to leave.

You are describing a typical reaction to chloramines, not chlorine. Public pools have a very high bather load so as the day goes on the amount of organics in the water increases and so do the amount of chloramines (or combined chlorine). This is not a problem for a properly cared for residential pool because the bather load is much less (assuming the pool is kept at the proper FC level for the CYA level). Most public pools are fine first thingk in the morning when they open but by mid afternoon many people start having red eyes and other symptoms. There will also be a pronounced 'chlorine' smell from the water. Chorine does not really smell, this is the smell of cloramines.

A heat wave would not cause an algae outbreak unless you were not paying attention to your chemical levels (FC and pH) or perhaps your CYA was too low and the FC was burining off too fast. If you had been testing your water and keeping it adjusted this would not have hapened. With a salt pool you should never let the FC drop below 5% of the CYA level and you should keep the CYA at the manufacturer's recommened maximum which is usually 80 or 100 ppm so the FC should NEVER drop below 4 or 5 ppm and ideally should be 1 ppm higher than this minimum. If you do this you will not have an algae outbreak no matter how hot the weather.

When you post your test results also post your make (and model) of SWCG so I can reference what your CYA should be. I will also post other recommendations for chemical levels that will make your salt pool as stable as it can be.

As far as testing goes, you should be testing free chlorine an pH daily (or at least 3 times a week), TA weekly, and CH, CYA, and salt (and borate if you added it to your water) weekly if your have a lot of water replacement such as an autofill or a sand filter that you backwash weekly or a lot of evaporation and spashout that requires a lot of topping off to monthly (for pools open year round) or once or twice a season (for pools that are winterized) ).

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Free Chlorine = 2.0

Combined Chlorine = 0

pH = 7.2

CYA = 50 ppm

total alkalinity = 100

calcium = 260

I do not check my pool chemicals that often - maybe twice a week when people are swimming more or once a week when they are not. The brand of Saltwater chlorine generator I have is Aqua Rite. I'm not sure what the model is but there is a number - 3A0802 - it says GoldLine and it's about 5 years old if that helps.

I added baking soda yesterday, and today the pH is still a little low. The water looks a little cloudy and walls are greenish.

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Ok, your FC is way too low and so is your CYA, TA is too high. We will get you fixed up.

Here are the numbers you want (in the order to get them adjusted:

Salt about 3200 ppm (a few hundred (200) ppm high or low is ok but this is the number to shoot for!)

CYA 80 ppm (and keep it here)

FC 4-5 ppm

Lower the TA to 70 ppm and keep it there. Do not raise it until it drops to 50 ppm.

pH -- don't drop it below 7.6, ever ( unless you are trying to lower the TA). The lower you put it the faster it rises! Wait for it to climb to 7.8 before dropping it back to 7.6

Get the calcium up to around 350 ppm to 450 ppm to keep the water balanced for the plaster finish.

These numbers will insure that you do not get an algae outbreak when you 'have a heatwave'. You will probably never need to shock the pool and you should find that your combined chlorine stays at 0 ppm. (The only reason to shock a salt pool is either because of CC or algae) It will also maximize the pH stability and minimize your acid additions to maintain the pH (since SWCGs tend to make the pH drift upward). Keeping your pool at these numbers will insure that the water is balanced in relation to the plaster surface of your pool at a temperature range of 70 to 90 degress so you will not have to worry about damage to the plaster because of unbalanced water.

Most imporatant of all, these numbers will keep the water safe and non irritating to your 'bather'.

The reason the water looks cloudy and the walls are greenish is because YOUR CHLORINE LEVEL IS TOO LOW AND SO IS YOUR CYA!!!!!!!

Shock the pool to 20 ppm and wait for the FC to drop to 10 ppm before allowing anyone into the pool.Brush the pool well after shocking. You will need aobut 4 1/2 gallons of laundry bleach (6%) or 2 gallons and 1 qt of 12.5% pool chloirne to shock you r pool to 20 ppm (added all at once). It will take about a day or two for the chlorine level to drop back down. Then get the CYA in there and go down the list above and get the other parameters adjusted.

NOT testing your water is like ignoring the gas gauge and warning lights in your car. You won't know there is a problem until the car stops working. If you monitor the gas, oil, coolant, etc. you can add them as needed BEFORE there is a problem.

The ONLY thing the SWCG does is automate the addition of chlorine to your pool, It does not allow you to ignore the other water parameters and you still have to make sure that it is adding the correct amount of chlorine for your bather load.

So:

1. shock the pool to kill the algae

2. bump up the CYA to 80 ppm and make sure your salt is about 3200 ppm

3. adjust the SWCG to maintain your FC at 4-5 ppm (once you have achieved 80 ppm CYA)

3 drop the TA to 70 ppm (stop adding baking soda!!!!!)

4.keep the pH between 7.6 to 7.8.

5 bump up the calcium to between 350 to 450 ppm

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It's been a few days and here are my current numbers - what do you think?

10 ppm FC

0 CC

7.6 pH

TA 90

calcium hardness 260-280 (turns purple, not blue)

salt is a 3000

CYA was at 80 then I ran out of the chemical to test it...a few days ago

I took a sample of water to the pool store to test for phosphates after I shocked the pool and they said phosphates were at 0, but now my walls are starting to look green again!

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1. shock the pool to kill the algae

2. bump up the CYA to 80 ppm and make sure your salt is about 3200 ppm

3. adjust the SWCG to maintain your FC at 4-5 ppm (once you have achieved 80 ppm CYA)

3 drop the TA to 70 ppm (stop adding baking soda!!!!!)

4.keep the pH between 7.6 to 7.8.

5 bump up the calcium to between 350 to 450 ppm

Don't worry about phosphates, they are a non issue

Shock the pool to kill all the algae (add bleach to get the FC up to about 25-30 ppm and KEEP IT THERE until the algae is dead and then let it drop down below about 12 ppm before swimming.It will take a day or two.

How many hours a day do you run the pump and what is the output percentage on the salt water chlorine generator?

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Is there a general rule as to how long to keep the FC high (how long to "keep it there")?

I run the pump 5 hours a day and the salt water chlorine generator is set at 80.

Everything I read about calcium hardness in swimming pool water recommends having keeping it between 200-400. Is there a reason you recommend having it at the high end?

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First, about the calcium hardness. I calculated the calcium saturation index for the parameters I gave you (including the salt level) and they will give you balanced water over a wide temperature range that you are likely to encounter. If you keep the calcium where you have it you run the risk of the water being aggressive to the plaster finish of your pool and possibly cause damage (particularly if you drop the pH below 7.6). If you keep the water parameters where I told you the water will be balanced and you will also maximize the pH stability of your salt system. The overall interaction of all the water parameters need to be taken into account. This is why it is called water balance,

Getting to your recurring algae problem I would recommend dropping the output and increasing the pump run time so chlorinated water is introduced into the pool over a longer period of time, parasitically during the warmer months. I would recommend a pump run time of 8 to 10 hours and decrasing the output to maintain the FC at 5 ppm. Also brush the pool regularly to minimize the stagnent spots that most pools have. Brushing down the sides sets up currents in the water that 'stir it up' so you minimize the locally chlorine depleted spots that tend to get algae first.

As far as shocking, you want to keep the FC at shock leven until there is no more green and the combined chlorine is at 0 ppm. Usually, it a day is long enough but it really depnds on how bad the alge is and whither it is free floating or in a biofilm on the pool wall (which is harder to kill and requires a lot of brushing ot break up the biofilm).

Hope this helps you.

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Yes, you have helped me so much - thank you for all your advice! I will follow your recommendations. I appreciate all the help I've gotten on this board and all the money I've saved. I am excited to get my pool walls clean and white again, and for them to stay that way. I'll set my timer for the pump to run longer at a lower level of output too. :)

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Why is it that chlorine pools require a chlorine level of 1-3ppm and salt pools with a chlorine generator are recommended to be at 5-6ppm? Or do you recommend all pools to be at 5-6..

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Chlorine level is really dependant on the cyanuric acid level in the water The higher the CYA the higher you need the chlorine for the SAME activity. The recommendation of 1-3 ppm is really for an unstabilized pool.

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I used the pool calculator tool on the Internet to calculate how much bleach to use in my pool to raise the levels to 25-30, and 4 days ago I added 3 gallons of 10% bleach. I've brushed the sides several times every day. The green on the walls is about 70% better I'd estimate - the remaining green is very resistant. Now when I brush the sides I don't see anything coming off (no particles, just water movement). Yesterday I checked the chlorine level and it was about 18. Do you advise me to raise the level back up over 25 again and continue brushing the sides? Or do you think if I just keep brushing it will continue to get whiter since the chlorine level is still pretty high? All the other levels of pH and Alkalinity, etc. were great.

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As long as there is green keep the chlorine level up and keep brushing! If you don't have one, invest in a metal algae brush. It will break up the biofilm protecting the algae. Once all the algae is gone then you let it drop. Do you have any combined chlorine? Also, please post test result numbers if you want us to help you, Saying that all other lvels were great tells us nothing. If you post numbers we might spot something that you don't.

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I do have a metal brush and have been using it. Now the water is looking cloudy - my new neighbors are rototilling their yard and I am sure dirt is floating in my pool. The walls with algae are still not white but are whiter each day.

Today here are my numbers: Chlorine = 19, CC=0 pH = 7.6-7.8 (between), alkalinity 80, calcium hardness - 290. I couldn't test CYA because my test kit ran out of the chemicals for that one. Salt level is at 3000 - I've also been having a leak issue so it's depleting the salt. Trying to fix that at the same time.

After testing I added 1/2 gallon of 10% liquid chlorine (that's all i have left) I know 19 is not high enough to kill the remaining algae.

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If you have a leak you are not only losing salt but also loosing CYA. It is important to get more reagent and test it. If the CYA is low it would explain the algae outbreak.

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i fixed one problem - my filter o-ring needed to be replaced. Air was getting into the system. Things should run better now.

I went to the pool store to get new chemicals for my taylor test kit. They gave me some reagent to test the CYA - that is still at 80. BUT they did not have the chemical for the Taylor kit that tests the chlorine. They only have the 0001 and 0002, which must be different Taylor test kit chemicals? They sold me those because they told me they didn't even recognize the numbers on my little container and they don't carry that specific reagent. Since I need to test the chlorine, I bought their 0001 and 0002. After I got home I realized those are practically useless because for one thing I don't have the same color testers they had in the store, and because I cannot get a specific number for chlorine over 5. I guess I need to find a place on the Internet to buy more of the right reagent.

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Try either ordering directly from Taylor or order from Amato Industries (they have very good prices but are a bit slow on shipping). You can also order what you need on Amazon and other sources on the net. If you have the K-2006 as you said before you need the DPD powder and the FAS-DPD titrant for chlorine (and R-0003 for testing combined chlorine.) Most stores do not stock these (Accurate home test results are not in their best interest since they want to sell you as many chemicals as possible and one of the ways they do that is by having you come in weekly for water testing!) Hope this helps.

Did you see my answer to you in the "dirt in pool" thread?

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The reagents they sold you are for the K-2005 test kit, btw. If you do not have the K-2005 comparator block they are totally useless to you. Return them! The test kit you have is identical to the K-2005 except that you have a BETTER test for free and combined chlorine that uses different reagents and is a drop counting test instead of a color matching test.

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