question about chlorine in storage tank

[echo]

Will liquid chlorine sitting in a storage tank that is 12.5 % strength weaken/degrade at a faster rate than 12.5% diluted to 6 or 8%?

 

[JasonLion]

12% loses strength way faster than 6% or 8%. However, dilution is not always a good idea. Dilution can speed up the breakdown, depending on what impurities are in the water.

 

[echo]

12% loses strength way faster than 6% or 8%. However, dilution is not always a good idea. Dilution can speed up the breakdown, depending on what impurities are in the water.

Thanks for the quick reply.. I do have access to free reasonable amounts of reverse osmosis water from a small home system which I could use to dilute my 12.5% hypo with. In your opinion how much strength would 12.5% hypo lose sitting in a covered black hdpe storage tank sitting outdoors over a 2-3 month period?

 

[JasonLion]

Possibly quite a bit, though the exact amount very much depends on temperature. There is a chart towards the bottom of this page that can give you a general idea.

 

[echo]

Possibly quite a bit, though the exact amount very much depends on temperature. There is a chart towards the bottom of this page that can give you a general idea.

Thanks for the chart/info... I think I will dilute my hypo (with RO water) and just have the stenner pump inject it for a longer period of time.

 

[mas985]

The more you dilute the chlorine, the faster you will need to inject it into the pool to maintain the same FC level and the sooner you will need to refill the tank. How big is the tank and how much chlorine do you use in a week?

 

[echo]

The more you dilute the chlorine, the faster you will need to inject it into the pool to maintain the same FC level and the sooner you will need to refill the tank. How big is the tank and how much chlorine do you use in a week?

The tank I have holds approx 25 gal..( it an old water softener brine tank) I have been using 1.5 to 2 quarts /day of 12.5% hypo. Pool is a 15k gal fiberglass which was just installed fall of 2013. I'm located in western New York Daytime temps have been in the low 70's to low 80's nights have been in the 50's.. I expect as temps rise with summer upcoming, hypo usage may rise a little. Since I'm a new pool owner I've been testing every day and have been using 1.5-2 quarts/day so far

 

[mas985]

So assuming 2 quarts per day and if the chlorine is 12.5% initially then you will only get 50 days out of 25 gallons of full strength. When you dilute the chlorine, you will shorten the time between refills. So at 6% chlorine, that is 24 days between refills. 3%, 12 days, etc.

 

[echo]

So assuming 2 quarts per day and if the chlorine is 12.5% initially then you will only get 50 days out of 25 gallons of full strength. When you dilute the chlorine, you will shorten the time between refills. So at 6% chlorine, that is 24 days between refills. 3%, 12 days, etc.

But will my 12.5% still be at 12.5% say after 30,40 days just sitting in that storage tank

 

[mas985]

No, you would still need to take that into account. I was just trying to demonstrate that the more you dilute the chlorine, the faster it will be used up. There is a sweet spot where you would probably get the longest time between the refills which balances degradation with injection rate but is going to be a complicated calculation because the concentration changes over time and so the injection rate would need to change as well. So it is probably best to dilute as much as possible so you are dealing with a near constant concentration but it means refilling more often. I would first target a 3% concentration and see how that goes. That should last almost two weeks.

 

[echo]

No, you would still need to take that into account. I was just trying to demonstrate that the more you dilute the chlorine, the faster it will be used up. There is a sweet spot where you would probably get the longest time between the refills which balances degradation with injection rate but is going to be a complicated calculation because the concentration changes over time and so the injection rate would need to change as well. So it is probably best to dilute as much as possible so you are dealing with a near constant concentration but it means refilling more often. I would first target a 3% concentration and see how that goes. That should last almost two weeks.

I would be satisfied with refilling every 2 weeks .. I'm understand that using a diluted chlorine results in using more volume to get the same amount of chlorine (2qts of 6% hypo = 1 qt of 12%)

 

[mas985]

The other factor is your injection pump max flow rate and run time will factor in how much solution can get injected per day. You don't want that to extend your filter pump run time if possible.