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Is It Safe To Put Liquid Chlorine In Salt Water Pool?


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#1 aGrandma

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Posted 16 June 2010 - 01:04 PM

I have a saltwater chlorinated pool with an algae problem (see previous post). I have always used my saltwater chlorinator and granular shock (called genesis shock from Leslie's pool supply.) Is it SAFE for me to use liquid chlorine in this type of pool - because Leslie's has never told me to use it. I don't want to harm any equipment. If it is safe, how much should I use to kill algae in a 15,000 gallon inground gunite pool? And what kind should I use if there is more than one kind?

Thanks and sorry to sound like an idiot - so many questions. I want this algae killed!

#2 Mark

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Posted 16 June 2010 - 01:09 PM

Yes, it is completely safe to use and I have done so several times. Really the best and cheapest way to kill algae is with liquid chlorine. You want pure chlorine bleach with no additives. As to how much, it depends on your CYA level but about 40% of the CYA level should be enough. Most SWGs recommend 80 ppm for CYA so raise the FC to 30 ppm. You can use the pool calculator to determine how much bleach is need.
Mark (aka mas985)

18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater
Hydraulics 101; Pump Ed 101; Pump Modeling Tools; FSEC Solar Panel Information; Solar Heat Gain and Loss

#3 aGrandma

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Posted 16 June 2010 - 01:18 PM

Do you actually mean chlorine bleach like at the grocery store? Like Clorox? When is it safe for people to swim after shocking using chlorine bleach?

#4 aGrandma

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Posted 16 June 2010 - 02:45 PM

I'm confused. I tried to use the calculator and read your directions and am not sure how much bleach to use. My pool is 15,000 gallons. I currently have 3.0 ppm free available chlorine. How much bleach would I use to raise the FAC to the recommended amount to kill algae?? My CYA is 60. Total alkalinity is 110. Water PH is 7.4 Total available chlorine is 3.0.

#5 Mark

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Posted 16 June 2010 - 04:25 PM

In the first box put 15000 for the gallons. In the second row, put 3 ppm in the left box and 24 ppm (60 * 0.4) in the right box. That gives, 653 oz of 6% bleach which is about 5 gallons. However, you will probably need more since it will get used up cleaning the algae. The goal is to maintain a high FC overnight until all the algae is killed.

Yes, you can use unscented 6% bleach from the grocery store but make sure it doesn't have any other additives. Walmart usually has the lowest cost generic bleach but sometimes it is sold as 96 oz jugs so you will need 7 gallons. It seems like a lot but it is less expensive than using the powered shock.
Mark (aka mas985)

18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater
Hydraulics 101; Pump Ed 101; Pump Modeling Tools; FSEC Solar Panel Information; Solar Heat Gain and Loss

#6 aGrandma

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Posted 17 June 2010 - 12:01 PM

Last evening I added 5.5 bottles of chlorine bleach to my pool. This morning I took a water sample to the pool store and now the FAC = 5, the TAC = 5, the CYA = 80. So do I need to add additional chlorine to keep it shocked for 2-3 days? If I use the calculator and put 5 in the 1st box, and 32 ppm in the 2nd box, it tells me to add more.

#7 polyvue

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Posted 17 June 2010 - 05:56 PM

Last evening I added 5.5 bottles of chlorine bleach to my pool. This morning I took a water sample to the pool store and now the FAC = 5, the TAC = 5, the CYA = 80. So do I need to add additional chlorine to keep it shocked for 2-3 days? If I use the calculator and put 5 in the 1st box, and 32 ppm in the 2nd box, it tells me to add more.

You're aiming for a shock level of 32 PPM Free Chlorine(FC)? For CYA = 80 this sounds about right. The trick to successful shocking is to very quickly raise the Free Chlorine to shock level (in other words, have enough bleach or liquid chlorine on hand and add it all at once) and then HOLD it at that level for several days or until there is no more than a 1 PPM loss of chlorine from evening until early morning, and the pool is crystal clear. This often means testing several times a day (much easier when you have your own test kit) and adding chlorine through-out the day as needed to maintain the 32 PPM. If you try to cheat this procedure (let it go for a day or two), the algae may re-group and you'll be fighting this all summer.

Keep the pump running all day and all night, brush the sides and floor of the pool and clean out skimmer/pump baskets at least once a day, and clean/backwash your filter when the pressure climbs to 10 PSI over normal.

Read through Defeating Algae and see if this doesn't make sense in your situation. Post back with questions. Many folks here have gone through this tunnel and emerged unscathed from the other side.
~14,000 gallon in-ground 16'x29' white plaster Pool w/spa Aug 2007; Goldline Aqua Logic AQL-PS-8 control w/Aqua Cell 15 Salt Water Chlorination (SWCG); Hayward TriStar 1HP (1.85 SF) main and 1.5HP (1.60 SF) spa pumps; Polaris 280 cleaner; Hayward Swimclear cartridge filter C4025; Tankless SP-18-4 electric heater; Hayward ColorLogic LED lights

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#8 jkusmier

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Posted 17 June 2010 - 09:56 PM

Well, you've already learned how to use the pool calculator! Polyvue is absolutely right about shocking procedure - and you will need more bleach to reach proper shock levels w/ a CYA level of 80. Which reminds me of something I forgot to mention- if you don't have a salt pool, you'll have to add ALOT of bleach to reach proper shock levels (40% of CYA) and to maintain a daily FC level of 5% of your CYA level. Others hare may disagree, but if you don't have a salt pool, you might consider lowering your CYA level to 40-50ppm. With CYA at 40-50ppm, you'll still be giving your chlorine alot of protection from sun/UV exposure (a pool with no CYA can lose 50% of its chlorine in 30 mins. of mid-day sun), but won't have to manually add as much bleach to shock or to maintain daily chlorine levels at 5% of CYA.

Unfortunately, CYA stays in the water and the only way to lower your CYA is to partially drain/refill your water. Unfold the drain hose on your pump and run it out onto your lawn, stop the pump, set the filter to waste, close the skimmer valve (once the water level drops below the mouth of the skimmer the pump will be sucking air - you want to drain using the main drains on the bottom of the pool) and restart the pump. If your FC/chlorine is around 5-6ppm when your drain it shouldn't damage your lawn.

Once you refill, you'll want to have your levels tested again. For a vinyl-lined or fiberglass pool, calcium/CH of 120 and TA of 80 are fine. CH should be 200ppm for a concrete/gunite pool.

#9 aGrandma

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Posted 18 June 2010 - 09:06 AM

2 days ago my CYA was 60 and FC was 3. According to the calculator I needed to add 5.5 96 oz jugs of bleach, which I did that day.

Yesterday (after adding bleach the night before) my CYA was 80 and FC was 5. Using the calculator, am I correct that the amount of bleach needed to keep the shock up to the level it needs to be is to add an additional 5.5 96 oz jugs of bleach???

Sorry, math is not my strong point. The calculator is a little foreign to me.

As of now my water is crystal clear - really beautiful, but one wall has a tinge of green on it still. I removed two plastic covers off the wall yesterday and behind them was a lot of green/black junk that I scrubbed off yesterday. There is still some after running the filter all night which I will scrub again...Is that green and black scum algae?

When shocking the pool to kill algae, and using the calculator, are the two main things I'm looking at the Free Available Chlorine and the Cyanuric Acid? The CYA increased from 60 to 80 overnight with the addition of the bleach, is that to be expected?

Any additional advice you can think of?? I really want this algae gone once and for all...Thanks so much for all the advice so far!!

#10 Mark

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Posted 18 June 2010 - 11:19 AM

Did you do the CYA measurement yourself? If not, you will likely get a large variance in readings from pool stores. It is one of the hardest measurements to be consistent with so it is best done by the same person each time and preferably by someone who cares (you). But for the purpose of cleaning up your pool, probably best to assume the worst case of 80 ppm with a FC target of 32 ppm. To go from 5 ppm to 32 ppm, you will need about 9 jugs of 96 oz chlorine.
Mark (aka mas985)

18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater
Hydraulics 101; Pump Ed 101; Pump Modeling Tools; FSEC Solar Panel Information; Solar Heat Gain and Loss

#11 polyvue

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Posted 18 June 2010 - 11:23 AM

What Mark said.

It's good that you're investigating places the algae can hide (the green and black scum is probably algae) and cleaning these areas; keep an eye on your filter and hose off the cartridges when necessary (or backwash, if you have a DE or sand filter) --- but the most important thing you can do is to get the chlorine up to a high level and KEEP it there, constantly filtering.
~14,000 gallon in-ground 16'x29' white plaster Pool w/spa Aug 2007; Goldline Aqua Logic AQL-PS-8 control w/Aqua Cell 15 Salt Water Chlorination (SWCG); Hayward TriStar 1HP (1.85 SF) main and 1.5HP (1.60 SF) spa pumps; Polaris 280 cleaner; Hayward Swimclear cartridge filter C4025; Tankless SP-18-4 electric heater; Hayward ColorLogic LED lights

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#12 aGrandma

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Posted 18 June 2010 - 04:02 PM

I moved this topic to the other board "water chemistry" - sorry I had not noticed that before. I keep having more questions!!




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