Cannot Get Any Chlorine Into My Pool

by David
(Canada)

Pool is 40 x 20, approx 135,000 litres (36,000 US gals). Sand filter is new this year. Ph is 7.6. Total hardness is 220. Alkalinity is 150. Cyanuric acid is 70. Copper, iron and TDS not tested. These are the readings from my pool center and they match pretty closely my own readings (main difference would be CA where I get 30-50). Free chlorine is 0. Water is crystal clear.


Recent history... Toward the end of last season, I couldn't get any chlorine into the pool. Eventually figured out the CA was too high. So I closed the pool a couple of weeks earlier than usual, partially draining it to winterize. Opening beginning of May, I had moderate algae - apparently a lot of pools in this area had the same problem. Cleaned up within 48 hours using chlorine shock and algecide.

Initial readings (5 May)were free chlorine 1.0, PH 7.4, hardness 160, alkalinity 140 and CA 20. Added 12 kilos (25 lb) calcium booster. Readings on 28 May were free chlorine 0.2, PH 6.8, hardness 220, alkalinity 90, CA 70. Added 15 lb baking soda and 4 kilos (9 lb) PH +.

Readings on 10 June were free chlorine 0, PH 7.6, alkalinity 140, CA 70 (hardness not tested). Advised to shock the pool repeatedly. Over the weekend of 14 June added 1.5 kilos (3.3 lb) of hypochlorite on four occasions - a total of 13 lb. No chlorine in pool between or after applications. Tested again on 18 June to get current readings. Advised that there "might" be algae still in the water that had not yet bloomed. Added 1 litre high concentrate algecide, circulated 4 hours, turned off pump overnight.

No visible evidence of dead algae in the morning. Shocked with 1.5 kilos hypochlorite. Chlorine reading 4 hours later - zero.

Between these interventions, the pool is shocked weekly with about 1.5 lb hypochlorite and treated with 200 ml high concentrate algecide (8 or more hours later). Stabilized chlorine pucks are added to an in line chlorinator. No idea what further action makes sense.




Thanks for the question David

First I'd encourage you to use liquid chlorine as calcium hypo not only has a pH of 12, which may increase the pH and acid use to bring it back down, but it also increases the hardness of the water, especially with frequent shocking.

Next would be to invest in a good test kit. I use and recommend the Taylor K-2006. A little more expensive but well worth it.

Algaecide is used for preventative measures only, not to kill already existing algae. I've cleared up dozens of pools without using a drop of algaecide. If you're using an algaecide you'll want a PolyQuat 60. Never use metal or copper based because you're opening yourself up for metal stains. These can be difficult to get rid of, not to mention pretty expensive.

It seems like your readings are not that far off. The CYA is just a bit high at 70ppm. The range is 30 - 50ppm. Once it gets to 80 - 90ppm it'll be time for a partial drain and refill. I'd lay off the chlorine tabs for now. As the CYA increases through the use of tabs you need to increase the chlorine as well.

The TA range is 80 - 120ppm. You have 140ppm which is a bit high. Just a little acid will bring that down. I'd start with 1 qrt. of acid. Pump motor off and add acid into the deep end. Sweep the bottom very gently and allow to sit for 3 - 4 hours. Then pump back on to FILTER for 10 hours, retest the TA and pH, and make another adjustment if needed.

Please don't waste your money on anything that's called pH Up or TA Up. It's all baking soda, either sodium bicarb or sodium carbonate. 20 Mule Team Borax can also increase the pH without much happening to the TA. I just saw a box of baking soda at the grocery store for 4 lbs. at $4.99. The same 4 lbs. at the pool store would be about $50.

What you may have is what's called a "chlorine demand". This can happen for a couple of reasons. The first is a fast acting chlorine demand caused by ammonia. This can happen when bacteria may have converted the CYA into ammonia. In this case it will take a LOT of chlorine to get rid of it. You can get an ammonia test kit from a fish/aquarium store to measure the ammonia amount in the pool. If you do have ammonia there's an equation and test you can perform to see just how much chlorine you're going to need.

The 2nd is slow acting chlorine demand that is caused by dead algae that needs to be removed or a filter that needs to be cleaned.

If you choose to get the ammonia test kit then you'll want to do the test. It's a little much but it can take the guess work out of the amount of chlorine you'll need. I rarely go to or endorse other sites but this one I do trust and have no affiliation with.

http://www.poolforum.com/pf2/showthread.php/16973-Bucket-testing-for-chlorine-demand

I'd first get a cheap ammonia test kit then go from there.

Hope this helps and have a great Summer.

Robert

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Chlorine Is Still Too High

by John
(Phoenix, Az. USA)

Have lowered my chlorine tabs to one, closed the tab floater doors to almost completely closed and chlorine is still at a three!

What else should I try?




Thanks for the question John

Honestly, you have a "problem" that most people wish they had. Most seem to not be able to keep chlorine in their pools.

If the chlorine level is at 3.0ppm and stays there, count your blessings. A good chlorine level for a home pool is between 1.5 - 3.5ppm. You're at 3.0ppm, which is very good.

Normal use and the Arizona sun and heat, of which I'm very familiar, will eventually eat away at your chlorine level. Be sure you're keeping the stabilizer (CYA) between 30 - 50ppm.

But, if you really want to get your chlorine level down, here are the two ways to do it.

First, you can drain 1/3 - 1/2 of your pool water, refill, and balance out the chemicals.

2nd, use a product called Thiosulfate. This is a chlorine neutralizer. I would recommend using this only in extreme situations. It can mess with your chlorine reading. I use it at the Y pool when I need to shock. I don't like to use it, but I need to because the chlorine level must be dropped (forced) down to a safe level for the swimmers.

I don't have the luxury of time and allow it to come down naturally. If I were you, I'd just leave the chlorine alone.

Whatever you're doing to get it to hold and properly sanitize your pool, keep doing it. Remember that chlorine tabs. will slowly raise your CYA so test that weekly.

The only way to decrease the CYA is the do a partial drain. There's no chemical for that.

Hope this helps and have a fun and safe swimming season.

Robert

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