Chlorine advice

stanwMay 1, 2013

I'm new to home and pool ownership.My pool is fairly large (not sure how many gallons) and I currently have a pool guy taking care of it once a week. I have a floater in the pool with chlorine tabs also. Two days after the pool guy was over my chlorine levels were a bit low. I had them checked at a pool store. The pool store is telling me its because my pool guy uses liquid chlorine and it evaporates quickly, and they want to sell me more expensive chemicals. My pool guy tells me that I have too much salt and calcium in my pool and I should drain and refill it because it is not holding the chemicals.

1. Do you guys use standard liquid chlorine or the more expensive powder? Does it pay to use the more expensive chlorine vs. standard liquid?
2. How often do you put chlorine into your pool during the week?
Is it normal that chlorine is added on Thursday and already low two days later?

Thanks for any insight!

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I use liquid chlorine. 12% versus the standard 5-6% you'll find in the laundry section of your store.

In a nutshell, free chlorine gets consumed due to two things; it gets broken down by the sun (UV), and it's consumed when killing unwanted organics in your pool (algae, for example).

You can minimize the amount of chlorine that is lost to sunlight by using a chlorine stabilizer or conditioner. Usually referred to as "CYA" or cyanuric acid.

CYA does two things: It protects the chlorine from being broken down by sunlight, which is important in an outdoor pool. It also combines with chlorine to lower the active chlorine concentration in the pool, that second part is what prevents chlorine from being to hard on swimsuits, hair, skin, etc.

"Stabilizer" and "Conditioner".

If you use liquid chlorine, you'll need to add CYA separately. You need to be careful when dosing CYA though, because you don't want too much. At too high levels, you'll need more and more chlorine to get the sanitation done.

If you're using tri-chlor pucks, they have CYA in them. While that sounds handy, over the course of a season it can result in the CYA level getting too high in the pool, and high CYA levels make chlorine less and less effective, so you need more and more and more and...

Once you get your CYA level set, it usually maintains for the entire season. You might lose some due to water loss; backwashing, vacuuming to waste, splashout, etc. But for the most part, once you get it where it needs to be you're good to go. If your CYS is sky high, I think the only practical way to lower it is by draining your pool a bit then refilling with fresh water.

You always need to dose chlorine. How much depends on how much is being used up in the pool during sanitation or being broken down by sunlight.

I recommend you get a good test kit. Not strips, but instead get something like a Taylor test kit. They are more accurate than strips. Learn to use the kit. Use it daily for a week while you get used to learning about your pool's chemistry, and while you bring things into balance. Then you'll probably just need to test once or twice a week throughout the rest of the season.

1. Do you guys use standard liquid chlorine or the more expensive powder? Does it pay to use the more expensive chlorine vs. standard liquid? As stated, I use liquid. It allows me to better control the chemistry of the pool water myself. I'm not totally anti-tabs. I travel a lot, and if I'll be gone for too long I'll toss a few tab floaters in the pool to maintain things while I'm gone.

2. How often do you put chlorine into your pool during the week? When I'm getting the pool squared away, I dose daily. If my pool gets regular use, I dose daily. If it doesn't get used regularly, then I might dose every other day.

Is it normal that chlorine is added on Thursday and already low two days later? It could be normal. You might have organics in your pool. Just enough to cause the chlorine to be used up during sanitation, but not so many organics that you can see an algae bloom, for example. Or your CYA levels might be low, so the sun's UV is breaking down the chlorine. Or a combination.

You need to think of chlorine as a consumable, which is is. It needs to be replenished. Tabs replenish as they dissolve. But depending on the the rate that they dissolve and the amount of chlorine your pool demands, you might need two floaters each full or tabs, 4 or 6 tabs in the pool at a time.

If you get to the point where you feel comfortable using 12% Chlorine, you can does your pool daily. A pint a day. A quart a day. Again , it depends.

So get a Taylor test kit. Test. Record the values. Dose the pool. When starting, it's best to go slowly. Don't try to solve your pool's water ills in one day. Test. Add a little today. Test tomorrow, then add more to tweak things.

I tried referring you to another website that has a pretty good "pool school" primer and a good "pool calculator" for helping to figure out chemical dosing, but this forum considers it spam so it won't let me add the links.

    Bookmark   May 1, 2013 at 11:20PM
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Thank you so much for your detailed response!!!!!!! This is starting to make more sense, my pool is surrounded by trees, leaves and other vegetation that are constantly falling into the pool.

I have been using liquid chlorine up to this point along with tabs in a floater, however, I purchased some packs of Chlor Brite Granular Chlorine that indicate "Available Chlorine 55%" and I also bought some Fresh N Clear Oxidizing Shock that the pool store recommended for keeping the chlorine last longer.

1. Is the Oxidizing Shock that I purchased the same thing as the "CYA" or cyanuric acid that you are recommending?

2. I am using a floater with Chlorine tabs in it. Is this what you are referring to as "tri-chlor pucks?" The bucket the tabs came in indicates they are Stabilized Chlorinating tabs.

3. How do you check for CYA levels? Can a test strip or the Taylor test kit check this?

4. You mentioned "If you get to the point where you feel comfortable using 12% Chlorine, you can does your pool daily. A pint a day. A quart a day. Again , it depends."

Are there issues with using 12% chlorine? You said where you feel "comfortable using 12%" What do you mean by that?


    Bookmark   May 8, 2013 at 8:59PM
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StanW - in order to maintain your pool properly you need to know what you have. What type of pool, what size (yes, calculate how many gallons), what type of pump/filter. Does it use a salt water generator, etc.

Once you know what you have, you then need to know where your at chemicals wise. This means properly testing your water. I recommend getting your own test kit in order to not rely on pool stores that make money by selling you stuff or a pool guy that looks at your pool once a week or so. Your pool store is wrong by saying liquid chlorine evaporates quickly and of course they want to sell you more stuff. Your pool guy is wrong by saying high calcium and salt is preventing other chemicals from "holding"??? Get informed so you will know what's right/wrong.

I recommend reading up on proper pool maintenance. I use what is known as the BBB method. Bleach, baking soda and borax. Bleach adds chlorine which sanitizes your pool. You must have enough bleach to kill off stuff. You need to read up on how much bleach you need for the size of your pool. Liquid bleach is the most recommended because it only adds chlorine and nothing else unlike all the other products sold by the pool store. The use of pucks/sticks are Dichlor and trichlor which add CYA. Cal-hypo which adds CH. In some cases you want to add CYA and CH but only until you get them to the correct levels.

    Bookmark   May 9, 2013 at 8:55PM
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This should be required reading for all pool owners. JasonLion at Trouble Free Pool dot com created it and everything you need to learn is there...

BBB for Beginners

BBB stands for Bleach, Baking Soda, and Borax, three common household chemicals which can replace expensive pool store chemicals. The BBB method of taking care of your pool focuses on using simple techniques that don't cost too much. Using the BBB method, you avoid putting anything in your water that you don't need and which may cause problems. This allows you to save money and spend your time swimming, instead of driving to the pool store to buy yet another expensive solution to a problem you didn't need to have in the first place.

The BBB method of pool care was originally popularized by Ben Powell at his web site and on his forum, The PoolForum.

The keys to a beautiful pool are consistency, testing, and chlorine. You need to be consistent. Spending just a couple of minutes every single day can save you hours and hours of work latter on. You need to test the water so you know what is going on and can figure out what to do to keep everything in balance. And you need to use chlorine.

None of the alternatives to chlorine works reliably and consistently in outdoor pools. Almost every problem people have with chlorine comes from pools that are not properly maintained. If you keep a chlorine pool the right way, people will ask you what you are using instead of chlorine. Almost all of the problems people associate with chlorine are actually problems that come from bad pool maintenance.

The best investment you can make in your pool is a top quality water test kit. Accurate water test results will save you time and money again and again. The TF Test Kits TF100, Taylor K-2006, and Leslie's Chlorine FAS-DPD Service Test Kit are the current stand-out choices on the market. All three include the FAS-DPD chlorine test, and are based on Taylor chemistry.

Testing and Adjusting

Every day you should measure your chlorine and PH, and adjust each as needed, based on your test results. Get into a routine of testing and adjusting the water at the same time every day. The best time to test and adjust is in the evening, but if another time works better for you, go ahead and do that. Once you get used to this simple routine, it will only take a couple of minutes a day.

Once every week or two you should test and adjust total alkalinity (TA) and, if you don't have a vinyl pool, calcium hardness (CH).

At the start of the season, and any time there has been significant water replacement, you should measure and adjust cyanuric acid (CYA). If you are using salt or borates in your pool, you should measure them at this time as well.

To adjust a level, measure your current level and enter it into the Now column of The Pool Calculator. Enter your desired level into the Goal column. Assuming your pool volume has been entered correctly, The Pool Calculator will then should you how much chemical to add to adjust the level. In several cases, The Pool Calculator will offer more than one possible chemical. In those cases, follow the advice below under the individual water test factors for which chemical to use.

When adjusting levels, it is usually best to work your way up towards your goal, instead of making the change all at once. First add perhaps 2/3rds of the amount indicated, allow that to mix into the water with the pump running for an hour for liquids, two to four hours for most powders, and a week for CYA. Then test the water again and continue adjusting from there. Chlorine is an exception to this rule: go ahead and add the full amount of chlorine all at once.

Chlorine (FC and TC)

Chlorine sanitizes your pool, killing bacteria, germs, and algae. Chlorine is used up in the process of keeping your pool safe, and is also consumed by sunlight. You need to add new chlorine regularly to maintain appropriate levels.

Chlorine can be measured as free chlorine (FC) or total chlorine (TC). TC counts both FC and combined chlorine (CC). You always want CC to be zero, and usually it is, so normally the TC test can be used to measure FC. But when something goes wrong, CC can often be greater than zero, and then it becomes important to measure FC and CC separately.

The FC level you are aiming for depends on your cyanuric acid (CYA) level. You can use The Pool Calculator to find the appropriate chlorine level to aim for, based on your current CYA level. Enter your CYA level in the Now column and then look at the blue Suggested FC Levels section towards the bottom for the normal range. Or, you can use Chem Geek's Chlorine/CYA Chart for the min and target numbers, or Ben's Best Guess chart. Each of those gives you a range of chlorine levels that may be appropriate for your pool. You never want the chlorine level to go below the lower number.

Add chlorine to the pool with standard household bleach. Pour the bleach slowly into the water in front of a return jet. Look for unscented or "original scent" and note the percentage. Bleach is commonly sold at 6% strength but some discount brands are lower, occasionally much lower. Bleach is sodium hypochlorite, the exact same chemical that many commercial pools use to sanitize their pools.

It is also fine to use a salt water chlorine generator (SWG) to add chlorine to the pool instead of using bleach. All of the other possible sources of chlorine have problems, they add things to the water that you don't usually want, simply cost too much to be practical, or are too dangerous to work with. Dichlor and trichlor add CYA. Cal-hypo adds CH. Chlorine gas is hazardous to work with. And lithium-hypo tends to be very expensive. There are cases where you want to add CYA or CH to the water and so use of dichlor, trichlor, or cal-hypo may be justified for a limited time, but this is rare.


PH is a measure of how acidic or basic the water is. PH below 7.0 can damage the pool surface and many pool heaters as well as causing eye and skin irritation. PH above 8.0 can lead to metal stains, plaster scaling, as well as eye and skin irritation. PH should always be maintained between 7.2 and 7.8, ideally between 7.5 and 7.8.

PH can be raised by adding borax. Pour the borax slowly into a skimmer or pre-mix it with water and pour that in front of a return. Borax is available at most grocery stores and places like WalMart and Target. Look for 20 Mule Team Borax, sold as a laundry booster, in a green box in the laundry aisle.

PH can be lowered with muriatic acid. Pour the muriatic acid slowly into the water in front of a return jet. Muriatic acid is sold at places like Home Depot, Lowes, and local hardware stores. It is often out near the pool supplies but sometimes is in the paint section. It is also possible to use dry acid to lower the PH. Dry acid is easier to work with than muriatic acid but costs more and should not be used with a SWG. Dry acid is sold by pool stores as PH Down, Lo-n-Slo, and PH Reducer.

Total Alkalinity (TA)

TA is a buffer that helps you maintain your current PH. The higher your TA is, the more difficult it will be to change the PH. However, higher TA levels combined with aeration will tend to raise the PH. The ideal TA level depends on your source of chlorine, and in many cases doesn't need to be at all exact. The usual range is between 60 and 90, though slightly lower and noticeably higher numbers are acceptable in some situations.

TA is raised with baking soda. Pour baking soda slowly into a skimmer. Look for Arm and Hammer baking soda, sold in grocery stores in the baking aisle. To lower TA, you bring the PH down to between 7.0 and 7.2 with acid and then aerate the pool to raise the PH back up. Aeration can come from from a waterfall, fountain, spa jets, kids splashing, SWG, rain, air compressor, or by pointing a return up to the surface so it breaks the surface. That cycle, acid and aeration, is then repeated as many times as is needed to lower TA to where you want it.

Calcium Hardness (CH)

CH is added to the water so that the water will not dissolve calcium out of your plaster or grout. CH can also help prevent foaming in spas. If you have plaster, pebble, stone, or tile in the water, CH should be kept around 200 to 400. Fiberglass pools and vinyl pools with a spa should keep CH around 220. Vinyl pools without a spa should keep CH anywhere under 300, which usually means you don't need to worry about it much at all.

CH is increased with calcium chloride or calcium chloride dihydrate. Distribute either form across the surface of the deep end of the pool. Calcium chloride is sold as an ice melter. Calcium chloride dihydrate is sold at pool stores as calcium increaser, Hardness Plus, and various similar names. To lower CH, you need to replace water, or if replacement water is extrememly expensive use a reverse osmosis water treatment.

Cyanuric Acid (CYA)

CYA protects chlorine from the effects of sunlight. The more CYA you have the less chlorine you will lose to sunlight each day. CYA also reduces the effective strength of the chlorine. At higher CYA levels you need more chlorine to maintain the same active chlorine level. If you have a SWG or get extreme amounts of direct sunlight on the pool, adjust CYA to between 60 and 80. Otherwise adjust CYA to between 30 and 50.

CYA can be increased by adding cyanuric acid, often sold as stabilizer or conditioner. CYA is just about the only chemical you need to go to a pool store to get. Check the label to be sure you are getting cyanuric acid since there are other products that use the words stabilizer and conditioner in their names. To lower CYA you must replace water, or if replacement water is extrememly expensive use a reverse osmosis water treatment.


Salt is required by a SWG and can also be used without a SWG to improve the feel of the water. Salt can be dumped directly into the pool as long as you brush it around into a thin layer and leave the pump running for several hours. Use solar salt, sold for water softeners, to raise the salt level. Water softener salt is sold by places like Home Depot and Lowes. Look for salt crystals in the blue bags. Avoid iron fighter, rust remover, or any similar additives. You can use potassium chloride but it costs more to begin with and you need to use 17% more to get the same salt level.


Borates can optionally be added to the pool to help control algae, reduce chlorine usage, buffer PH, and improve the look and feel of the water. The process of adding borates to your pool is beyond the scope of this article.

Everything Else

There are many other pool chemicals sold: clarifier, flock, phosphate removers, enzyme treatments, metal sequestrant, non-chlorine shock, and many others. Most of these do have some use in very specific situations, but none of them are required in most pools. You should not use any of these chemicals unless you know that you are in a situation where they are required.


The leading cause of pool problems is simply ignoring the pool. Your pool is like a pet: it requires constant attention. The number two cause of problems is adding chemicals you didn't need and don't want. Not only do these extra chemicals tend to cost a lot but they can also cause problems.

Follow the BBB method, spend just a couple of minutes a day taking care of your pool, and you can have a truly trouble free pool.

    Bookmark   May 9, 2013 at 9:01PM
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That is so helpful
I am getting stabilizer tomorrow

    Bookmark   May 15, 2013 at 12:54AM
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"I purchased some packs of Chlor Brite Granular Chlorine...

I googled that and it does have a stabilizer in it. So it's fine to use up until your CYA (stabilizer) levels are where you want them to be. Once there, don't use any more. That's a good time to transition to liquid chlorine.

1. Is the Oxidizing Shock that I purchased the same thing as the "CYA" or cyanuric acid that you are recommending?

Not at all. The stuff you bought it a non-chlorine shock. It's an oxidizer, based on potassium monopersulfate. By being non-chlorine, the idea behind using that product is that you can shock you pool and swim soon after. When shocking with chlorine you generally want to wait for the chlorine levels to decrease before swimming.

CYA is usually labeled as a "chlorine stabilizer" or "conditioner" something similar. Just check the ingredients and look for Cyanuric Acid or CYA.

2. I am using a floater with Chlorine tabs in it. Is this what you are referring to as "tri-chlor pucks?" The bucket the tabs came in indicates they are Stabilized Chlorinating tabs.

Yes. Pucks can have different makeups. If your pucks have stabilizer in them, then the same as my previous...use them until your CYA level gets to the appropriate level, then switch to liquid chlorine. Or anything else without CYA.

3. How do you check for CYA levels? Can a test strip or the Taylor test kit check this?

Some strips test for it. But strips can be inaccurate. The Taylor kits do test for it, or at least it's available as an option.

4. Are there issues with using 12% chlorine? You said where you feel "comfortable using 12%" What do you mean by that?

No issues at all. Some folk like pucks; toss 'em and forget 'em. But if you use them all season long, your CYA levels can skyrocket, and as the CYA rises you need even more chlorine. It becomes a runaway train, so to speak. The higher the CYA, the more chlorine you need for the chlorine to be effective.

Some are scared of gallon jugs of 12% chlorine. No need. Liquid chlorine is easy to use and dispense. I simply walk the perimeter of my pool and pour out some every 5-10 steps or so as I walk around the pool.

You'll eventually have a good feel for the chemistry of your pool. I swim laps each day, and for a generic day I know how much chlorine my pool needs each day to maintain a decent parts per million presence.

After a heavy wind storm, or right now, during the beginning of the two weeks that pollen and catkins fill my pool each day, I have to bump up the chlorine a bit.

If my kids have a big pool party, that's another time to bump the chlorine, after the party.

After opening my pool, once I get my water chemistry set, I usually test once a week.

    Bookmark   May 16, 2013 at 7:05PM
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One other note to add on chlorine since this thread has really good detail in it. Keep an eye on phosphates or food for ALGAE. It is a good idea to add a phosphate remover on a regular basis to the pool to keep the green walls at bay.

My last pool I used phosphate remover on a regular basis and never saw one green wall. I just had a new pool built a few weeks back and I will be doing the same. After a rain storm a little shock and phosphate remover and keep those filters clean !

    Bookmark   July 21, 2013 at 10:07AM
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This thread has been great!

A few years ago I was told I had algae due to phosphates, how much phosphate remover do you suggest I use for a 32,000 gallon pool?

Besides checking chemicals on regular basis (daily - every other day) is there anything else you suggest adding to keep my pool water crystal clear....want to prevent metal buildup on liner to, had that a few years ago when I used weekly pool service. Thanks.

    Bookmark   July 21, 2013 at 10:40AM
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