What is the effect temperature on chlorine consumption?

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cbredesen

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Bronze Supporter
Jul 25, 2015
35
Orlando, FL
I'm having trouble finding this information via search of in Pool School. I struggle a bit in the summer (Central FL, screened in 8000g plaster pool) to keep on top of my sanitizing. we have a solar heated pool and my wife likes it over 90F. We have compromised on around 86-87, higher and I just don't even wanna be in it because it isn't refreshing.

That said, I understand that sunlight consumes chlorine but how does higher operating temperature affect consumption?
 
Temp of the pool water does not contribute to your sanitation problems. Higher water temps can promote algae if the water is not properly chlorinated.

How do you chlorinate your pool?

What test kit do you use?

Post your own test results.

I suggest you read ABCs of Pool Water Chemistry
 
Thanks, I'm familiar with the ABC's. I couldn't find any references to temperature anywhere so thanks for the info. I'll post up some numbers in the future when I can take readings 1-2 days apart.

Edit: liquid chlorine; sorry I thought I had mentioned that.
 
Pool has been cloudy. Cartridge is about 2mo old and I cleaned it this past weekend (3 days ago). I SLAM'd the pool about 3 weeks ago trying to get head of the algae but I'm noticing that When I have the Cl up around 9.0 on Sunday, that by Wed or so it's back down sometimes to 3. Moderate bathing load, not heavy.

This seems excessive to me. My CYA is around 60; I had used some tablets (less than 20 over several weeks) earlier this season trying to stay on top of santitizer, so it's a little high.

Today's numbers:

FC: 2.5 :(
CC: I am out of reagent but I have never had CC that I can recall in the last 5 years.
pH: 7.6 (I'll add some acid)
TA: 65 (I'll add some soda)
CH: 360
CYA: 60
Temp: 85 degrees

So back to my original question, I see now that temperature doesn't really affect Cl consumption but to does enable algae growth. Is there a threshold after which it becomes too hard to contain? What should I be doing differently?

The way my pool seems to work is that I can't add enough Cl on the weekend to last most weeks. Is this normal? I am apparently going to have to SLAM again and start over. Ugh.
 
cbredesen said:
Pool has been cloudy. Cartridge is about 2mo old and I cleaned it this past weekend (3 days ago). I SLAM'd the pool about 3 weeks ago trying to get head of the algae but I'm noticing that When I have the Cl up around 9.0 on Sunday, that by Wed or so it's back down sometimes to 3. Moderate bathing load, not heavy.

This seems excessive to me. My CYA is around 60; I had used some tablets (less than 20 over several weeks) earlier this season trying to stay on top of santitizer, so it's a little high.

Today's numbers:

FC: 2.5 :(
CC: I am out of reagent but I have never had CC that I can recall in the last 5 years.
pH: 7.6 (I'll add some acid)
TA: 65 (I'll add some soda)
CH: 360
CYA: 60
Temp: 85 degrees

So back to my original question, I see now that temperature doesn't really affect Cl consumption but to does enable algae growth. Is there a threshold after which it becomes too hard to contain? What should I be doing differently?

The way my pool seems to work is that I can't add enough Cl on the weekend to last most weeks. Is this normal? I am apparently going to have to SLAM again and start over. Ugh.
Click to expand...

It's a bit tricky to isolate temperature because it often rises as the amount of UV light (angle and duration) hitting your pool increases. So the warmer temperature allows for easier algae growth and the sunlight breaks down the FC faster. Which is why CYA is important. To buffer the FC from the sunlight.

Bottom line is FC is a consumable and needs to be replaced routinely. I replace my FC constantly every day because I have a saltwater chlorine generator. But if you are using bleach, every two days would a very reasonable approach if not every day. What causes you to think your FC use is excessive? That's probably what is the root issue here. Your expectation is out of line with the normal behavior. FC usage of 2 to 4 or 5 ppm per day is normal in season.

HOWEVER, if your pool is not crystal clear, or you have any visible algae you need to SLAM as you didn't complete it the last time. Properly following the SLAM process doesn't 'get ahead' of algae, it eradicates it. Which you likely haven't done. So we are all clear what is the visible status of your pool today?
 
A pool will consume 2-4 ppm FC per day. You lost 6 ppm over 3 days - average 2 per day.

What testkit are you using?

Replensih your spent reagent - if your other reagents are over a year old, just order a complete refill kit - Testkit Refills

Follow the FC/CYA Levels and use PoolMath to calculate what you need to add.

pH of 7.6 and TA of 65 (how did you measure 65?) Are just fine - no need to adjust now. You do need to add chlorine to reach the target range of the FC/CYA Levels.

If the pool has been cloudy, chances are you are having an algae bloom and need to follow the SLAM Process. While waiting for your replacement reagents, raise your FC to the upper limits of your target range based on the FC/CYA Levels and maintain it there - daily if need be. Going forward, you are going to have to test FC and add chlorine more than once a week - or consider adding a SWG.
 
Hate to pile on but neither of these need addressing:
pH: 7.6 (I'll add some acid)
TA: 65 (I'll add some soda)

Adding acid and baking soda to correct a pH and TA that are just fine is not needed.
 
cbredesen said:
So back to my original question, I see now that temperature doesn't really affect Cl consumption but to does enable algae growth. Is there a threshold after which it becomes too hard to contain? What should I be doing differently?
Click to expand...

Your pool is not really that hot in the grand scheme of things so you can safely stop worrying about any temperature effects. Mine is much hotter usually about 93°. Never less than 90 and often bouncing off 96° which is the point I actively cool it. No problems at all simply by maintaining my chlorine levels on a daily basis never letting it go below the suggested range in the fc/cya chart.

At 96F the pool is more reactive than at 86F and chlorine is consumed more (probably from oxidizing the solar cover which is always on when not swimming) but nothing excessive. It ranges between 1-3ppm per day depending on conditions/activity. Sounds like your pool is losing about 2 ppm per day. That's within normal.

Adding chlorine is a daily task not a weekly one.
 
mknauss said:
Hate to pile on but neither of these need addressing:
pH: 7.6 (I'll add some acid)
TA: 65 (I'll add some soda)

Adding acid and baking soda to correct a pH and TA that are just fine is not needed.
Click to expand...

PoolMath itself gives 70-90+ as the range for TA. pH is fine but I am frequently hitting 7.8+ so I try to keep it on the lower end. I agree this isn't part of the problem, it was just a comment about the numbers.
 

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proavia said:
A pool will consume 2-4 ppm FC per day. You lost 6 ppm over 3 days - average 2 per day.
Click to expand...

Every pool service I've ever had growing up or even in this house before I started maintaining has come once a week, no pucks. Crystal clear water during all bathing loads. I'm not saying you're wrong, but what are they doing that I'm not? Just using gobs more chlorine?

I'm not sure how I have been through this site multiple times over the course of years and never arrived at the fact that adding sanitizer is that frequent of a task, but here we are. I will adjust my mental model and figure out what to do when I travel, which is several times per year for several days or more.

I think a SWG may be the right thing for me at this point, I just suck at this. Thankfully you all are kind and helpful!
 
cbredesen said:
Every pool service I've ever had growing up or even in this house before I started maintaining has come once a week, no pucks. Crystal clear water during all bathing loads. I'm not saying you're wrong, but what are they doing that I'm not? Just using gobs more chlorine?

I'm not sure how I have been through this site multiple times over the course of years and never arrived at the fact that adding sanitizer is that frequent of a task, but here we are. I will adjust my mental model and figure out what to do when I travel, which is several times per year for several days or more.

I think a SWG may be the right thing for me at this point, I just suck at this. Thankfully you all are kind and helpful!
Click to expand...

For those who are just coming here, adding FC is often by pucks, so it's not a "frequent" task, but they just keep pucks in the feeder. For the pool services you mention, if they are not using pucks, then they are adding the amount of FC the pool needs to last for the week by way of liquid shock 12.5% (bleach/chlorine). So they may add 20 ppm of FC. So long as that's below SLAM level for your CYA, it's safe to swim in. But FC also depletes more quickly at higher concentrations. So if you normally use 2 ppm per day, you would likely need more than 14 ppm for a week. The best practice if dosing with liquid, is to add it from every day to every few days on the longer end to avoid both high FC levels and it's faster depletion rates.

But yes, SWCG's are a fantastic solution. Overall cost is about on par with liquid over time.
 
You can also get a stenner pump on a timer with 15 gallon tank and use liquid chlorine to maintain FC. Search the forum and you will see quite a few members use this method.
www.poolweb.com

S1G45MFH2A2SUAA - 15 Gallon Chemical Tank With 45MPHP10 Fixed Pump - 100 PSI 10 GPD 1/4 Inch - Stenner

This Stenner S1G45MFH2A2SUAA is a 15 Gallon UV resistent chemical tank with a 45MPHP10 Stenner chemical Pump. This system is 100 PSI, 10 GPD, 120 Volt and includes 1/4 Inch UV tubing. This combined chemical pump and tank system provides you a complete setup for your swimming pool..
www.poolweb.com www.poolweb.com
I fill mine about once per month and it runs for about 12 minutes 3 times per day (33k gal pool).
 
skimmerswimmer said:
You can also get a stenner pump on a timer with 15 gallon tank and use liquid chlorine to maintain FC. Search the forum and you will see quite a few members use this method.
www.poolweb.com

S1G45MFH2A2SUAA - 15 Gallon Chemical Tank With 45MPHP10 Fixed Pump - 100 PSI 10 GPD 1/4 Inch - Stenner

This Stenner S1G45MFH2A2SUAA is a 15 Gallon UV resistent chemical tank with a 45MPHP10 Stenner chemical Pump. This system is 100 PSI, 10 GPD, 120 Volt and includes 1/4 Inch UV tubing. This combined chemical pump and tank system provides you a complete setup for your swimming pool..
www.poolweb.com www.poolweb.com
I fill mine about once per month and it runs for about 12 minutes 3 times per day (33k gal pool).
Click to expand...
I'm looking at getting a Stenner for next year as I am in the same position as the OP of this thread with frequent vacations during the summer and wanting to reduce the frequency of chlorine adds. Do you have yours buried to keep it cool or just have it sitting on the ground? Also, do you have to store it inside during winter for freeze protection or can it be drained and left out just like the other pool equipment? Any benefits to adding chlorine multiple times per day in small doses vs. just adding the total dose for each day once in the middle of the night?
 
AndyTN said:
I'm looking at getting a Stenner for next year as I am in the same position as the OP of this thread with frequent vacations during the summer and wanting to reduce the frequency of chlorine adds. Do you have yours buried to keep it cool or just have it sitting on the ground? Also, do you have to store it inside during winter for freeze protection or can it be drained and left out just like the other pool equipment? Any benefits to adding chlorine multiple times per day in small doses vs. just adding the total dose for each day once in the middle of the night?
Click to expand...
My chlorine tank sits on the equipment pad. The grey color tank helps with the sun, but my equipment pad is in the shade all day except for an hour or two in the morning. When I close the pool for the winter, everything comes into the garage (pool pump, Stenner pump and tank, filter). The multi-port valve and the heater get covered. I'm not sure if there are any benefits to running the pump multiple times per day vs. once per day, but perhaps an argument could be made that testing FC should become more predictable/reflective of daily average FC even if done at different times of day since you're never adding a lot at once (similar to SWG).
 
bmoreswim said:
For those who are just coming here, adding FC is often by pucks, so it's not a "frequent" task, but they just keep pucks in the feeder. For the pool services you mention, if they are not using pucks, then they are adding the amount of FC the pool needs to last for the week by way of liquid shock 12.5% (bleach/chlorine). So they may add 20 ppm of FC. So long as that's below SLAM level for your CYA, it's safe to swim in. But FC also depletes more quickly at higher concentrations. So if you normally use 2 ppm per day, you would likely need more than 14 ppm for a week. The best practice if dosing with liquid, is to add it from every day to every few days on the longer end to avoid both high FC levels and it's faster depletion rates.

But yes, SWCG's are a fantastic solution. Overall cost is about on par with liquid over time.
Click to expand...

So this begins to fill in the picture. I quit using pucks years ago when my CYA was in the *hundreds*. I might look into a pump or liquidator but for now I'm going to make my routine every other day or so, and jack it up when I travel.
 
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