Minimizing Daily Chlorine Usage

[vik]

Basically, I'm trying to minimize my daily chlorine usage. My goal is to get to the point where I have to replace 1ppm a day at most. I prefer to hold my CYA stead by using unstabilized chlorine.

Does stabilized chlorine (dichlor) for some reason last inherently longer than unstabilized chlorine (bleach)?
Is there some way I can calculate the required amount of CYA to limit daily chlorine usage to 1ppm?
Are there any simple ways to reduce chlorine burn off?

 

[woodyp]

I think you're chasing a winged purple dragon at 1 ppm per day.

 

[Bama Rambler]

Why do you want to get to 1ppm or less?

You can construct a building around your pool and that'll cut out a lot of loss. I'm not sure you can get to 1 ppm per day every day but it'll probably get close. Oh yeah you can't let anyone swim in it either.

One type chlorine doesn't last any longer than any other type.

 

[vik]

That makes me a sad panda. What is feasible for an outdoor in-ground pool? For me raising the chlorine levels by 1ppm is 1 gallon of 12% bleach and it's $20 for 5 gallons of 12% bleach. So it gets expensive

 

[Bama Rambler]

That must be one huge pool! I get 100,000+ gallons in order for it to take 1 gallon of 12% to raise the FC by 1ppm.

2ppm is very obtainable. I do that with a CYA of about 60 ppm.

 

[vik]

I don't know the exact number of gallons but I'm reasonably sure it's between 90 and 100. Unfortunately, I had some equipment issues (that you helped me with) and I didn't get my filtration system going until yesterday. While it was broken, the pool went green. I put 10lbs of dichlor in last night and it was all gone this morning. Probably lost it all to the algae and it's still green. Going to liquid shock it Saturday night and go through my 40lbs supply of dichlor today and tomorrow.

 

[beezar]

You might not want to use dichlor when shocking unless your CYA is really low, as it'll raise CYA forcing you to use more liquid shock or chlorine. What is your CYA level?

 

[JasonLion]

beezar, see this related topic.

vik, best to be more careful to keep your comments related to the current topic so this kind of confusion doesn't occur.

 

[chem geek]

Higher CYA levels will protect chlorine more from sunlight even with proportionately higher FC levels. For example, 6 ppm FC with 80 ppm CYA may lose somewhat under 1.5 ppm FC while 7.5 ppm FC with 100 ppm CYA may lose around 1.2 ppm FC. However, such high CYA levels are risky because if you let the chlorine get too low for too long or have any unusual event that requires you to shock the pool, then it will take extraordinarily high levels of chlorine for such shocking. We usually recommend around 50 ppm CYA as a reasonable compromise, but daily chlorine demand may be around 2 ppm FC at this CYA level and you'll need to add chlorine every day.

One way to minimize chlorine usage is to use a mostly opaque pool cover. That will usually get you to under 1 ppm FC loss per day where the loss is mostly related to the water temperature. Of course, with such a large pool that may be impractical unless the cover is automatic or you have some sort of enclosure. Another way is to use alternative means of controlling algae growth, but that usually costs extra either in mostly one-time dosing as with borates or in weekly addition as with PolyQuat 60. Another way to potentially lower cost is to use a saltwater chlorine generator -- though they normally aren't that much less expensive, they pay off more in larger pools since the chemical costs go up faster than the capital costs for that size of pool and the electricity cost to generate the chlorine isn't very much at all, but initial costs will be high for both equipment and salt.

Why is your pool so large? Is this a residential pool?

 

[vik]

Sorry Jason, I'll try to stay on topic. The reason I mentioned that I was using dichlor was that it would raise my CYA up but I did get off topic at the end there.

chem geek:
My pool is residential. I would love to have a SWG. However, we're planning to move out soon and this season is half done. If I could find one that's cost effective when taking into account that this is probably my last season tending this pool, I would 100% go for it. However, the cheapest solution I've been able to find is $2000 at least not including installation.

 

[chem geek]

Well, with 100,000 gallons, nothing is cheap.

For 2 ppm FC you need 4.3 96-ounce jugs of 6% bleach or 1.6 gallons of 12.5% chlorinating liquid. Prices vary, but at $1.25 for 96-ounce bleach or $3.50 for 1 gallon of chlorinating liquid this is around $5.40 to $5.60 per day or around $165 per month.

For 10 ppm CYA you need 8.3 pounds which at $3.26 per pound is $27 so to go from 50 ppm to 80 ppm is over $80 in order to save perhaps 0.5 ppm FC per day or around $40 per month.

For PolyQuat algaecide you need 90 ounces initial and then 30 ounces per week which at $20 per quart (32 ounces) is $56 initial plus $19 per week (about $80 per month) to save at least 1 ppm FC per day or around $80 per month so close to a wash unless you go to aggressively low FC/CYA ratios such as 2 ppm FC with 80 ppm CYA in which case you have a net $40 per month savings.

For 50 ppm Borates you need 239 pounds of boric acid which at $1.62 per pound is $387. Using 20 Mule Team Borax and Muriatic Acid would be less expensive, but still well over $200. This would also be to save perhaps $80 per month at best.

The fact is that a large pool is proportionately more expensive to maintain.

 

[Richard320]

You can reduce chlorine usage to zero this way..