How Often to Shock Pool?

[dcsmith]

I am still relatively new at pool ownership.
I maintain my chemistry pretty well with a specific eye on CSI.
My main question is if I maintain FC at between 2-4ppm, CYA 70-75, and TC has never been higher than .1ppm above FC, do I need to shock my pool? If so, how often, what type and amount of shock should I use?

 

[Jimrahbe]

Dave,

With a CYA of 70, your FC target is 5 ppm. Your minimum is 3.. With a CYA of 80, your FC target is 6 and your minimum is 4ppm.

Trying to keep your FC between the minimum and your target is a recipe for failure. You should be trying to keep your FC at 5 or higher.

If you follow this chart ..FC/CYA Levels you should never have to add Pool Store shock to your pool.

Why are you trying to keep your FC so low?

Thanks,

Jim R.

 

[ajw22]

In 20 years I have never needed to “shock” my pool using TFP methods.

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[dcsmith]

Dave,

With a CYA of 70, your FC target is 5 ppm. Your minimum is 3.. With a CYA of 80, your FC target is 6 and your minimum is 4ppm.

Trying to keep your FC between the minimum and your target is a recipe for failure. You should be trying to keep your FC at 5 or higher.

If you follow this chart ..FC/CYA Levels you should never have to add Pool Store shock to your pool.

Why are you trying to keep your FC so low?

Thanks,

Jim R.

Jim,
Sorry, I "miswrote". My target FC at a CYA of 70 is 3-5ppm.
My FC has been running between 4-5.4ppm and a CYA of 70-75ppm.

 

[proavia]

You can't read a CYA of 75. The scale on the tube is logarithmic and not linear. If CYA reads above 70, round up to 80.
Use the FC/CYA Levels
Trying to hover around the minimum FC for your CYA level will not serve you well long term. Shoot for the upper end of the target range - or even a couple ppm higher. Remember, the pH test is invalid with FC above 10.
There is zero reason to shock your pool if you follow TFP methods.

 

[dcsmith]

You can't read a CYA of 75. The scale on the tube is logarithmic and not linear. If CYA reads above 70, round up to 80.
Use the FC/CYA Levels
Trying to hover around the minimum FC for your CYA level will not serve you well long term. Shoot for the upper end of the target range - or even a couple ppm higher. Remember, the pH test is invalid with FC above 10.
There is zero reason to shock your pool if you follow TFP methods.

Jim,

I am using a photometric measuring device for all my measurements except for CH & recently TA. For those I use the Taylor drop test kits. The device still reads turbidity.
I am using the TFP FC-CYA chart. I'm also trying to keep in the middle range. It has been harder this year as we have had a lot of rain that causes overflow & dilution. I think I have had to add water once this Summer.
Thanks for the shock information. Local pool companies recommend shocking once per week! Perhaps for a public pool.

 

[ajw22]

Local pool companies recommend shocking once per week! Perhaps for a public pool.

Perhaps they like to sell you shock and other unnecessary chemicals???

 

[proavia]

My bet is that PoolLab tester is LESS accurate than you think.
How do you calibrate it and when was the last time it was calibrated?
If the results from your PoolLab are to be trusted, still use 80 for your CYA.

Moving forward, I'd recommend you seriously consider getting one of the recommended testkits - most probably the TFPro - Salt since you have a SWG.
Test Kits Compared

 

[Jimrahbe]

Dave,

When not using the TFP methods, you have to shock weekly so that you can keep algae at bay.

If you always keep your FC in the proper range with your CYA, then algae is not a problem, and shocking is not required.

The reason that I like running at my target and not the middle of the range is that I never have to worry if there is a rainstorm, a lot of sunshine, heavy bather load, etc. It means that I can relax and enjoy my pool rather than having to micromanage my FC production.

My wife just says it is because I am lazy...

Thanks,

Jim R.

 

[Jimrahbe]

Dave,

I have zero experience with the PoolLab 1.0 photometric test kit, but I do have a LaMotte ColorQ, which I like, but has its own issues.

I have three ways to test CYA and have found that the batch of CYA tablets makes a lot of difference in the readings. When I get a new tablets, I compare the results with the older batch. Sometimes they are pretty close and sometimes they are different by 20 ppm. I save the batches that are close, and discard the batches that are way off. Since I don't test CYA all the time, there are plenty of good tablets to use.

My point is that I can't blindly take the results from the CYA test that the ColorQ does, as an absolute correct value.

Thanks,

Jim R.

 

[dcsmith]

Perhaps they like to sell you shock and other unnecessary chemicals???

That goes without saying.
I've got most of my chemicals sourced, but still looking for 25# Calcium Chloride that isn't overpriced.

 

[Newdude]

DC, when do you run your SWG ? At almost 3X your pool volume you will only be producing a few hours a day (night) and the pool will likely behave more like a liquid chlorine pool.

 

[dcsmith]

DC, when do you run your SWG ? At almost 3X your pool volume you will only be producing a few hours a day (night) and the pool will likely behave more like a liquid chlorine pool.

My filtration system runs 7 hours a day - currently. The SWG is currently set to 50%. I believe this means it is running about 3.5 hours a day. The main filter pump runs at 35gpm.
I'm not sure your point.

 

[dcsmith]

Dave,

I have zero experience with the PoolLab 1.0 photometric test kit, but I do have a LaMotte ColorQ, which I like, but has its own issues.

I have three ways to test CYA and have found that the batch of CYA tablets makes a lot of difference in the readings. When I get a new tablets, I compare the results with the older batch. Sometimes they are pretty close and sometimes they are different by 20 ppm. I save the batches that are close, and discard the batches that are way off. Since I don't test CYA all the time, there are plenty of good tablets to use.

My point is that I can't blindly take the results from the CYA test that the ColorQ does, as an absolute correct value.

Thanks,

Jim R.

I agree with the variability of the reagent tablets. This is why I have switched to a Taylor drop test kit for Alkalinity. The CYA tablets seem to produce consistent results - no wild fluctuations, which would be a telltale.

 

[Newdude]

My filtration system runs 7 hours a day - currently. The SWG is currently set to 50%. I believe this means it is running about 3.5 hours a day. The main filter pump runs at 35gpm.
I'm not sure your point.

OK you should probably switch to following the LC side of the FC/CYA Levels. The SWG side of the chart was designed for all day SWG production. Your unit is off and not producing 20.5 hours a day. Using the LC side of the chart will keep you free and clear above minimum.

 

[dcsmith]

OK you should probably switch to following the LC side of the FC/CYA Levels. The SWG side of the chart was designed for all day SWG production. Your unit is off and not producing 20.5 hours a day. Using the LC side of the chart will keep you free and clear above minimum.

Who runs their pool filter 20 hours a day? My SWG seems to be producing sufficient amount of Chlorine running 3.5 hours a day.

 

[Jimrahbe]

dc,

A lot of people run their pumps 24/7.. It is just a difference in pool philosophy. You should do whatever works best for you.

The downside to generating all the chlorine your pool needs over a short period of time is that the pool continues to consume FC even when the pump is off. That means when the pump shuts off you need enough FC reserve to last you until the pump comes one again. As long as you know that just before the cell starts generating chlorine again, that your FC is still at your target level, then running only 7 hours a day will work just fine. The key is to test your FC just before the cell starts to make chlorine again and not just after the cell shuts off for the day.

I personally like to run 24/7, as I am making a little chlorine all the time and skimming all the time. I run mostly at 1200 RPM, so running 24/7 costs me less than $20 a month in electricity. It would be even less if I had a new IntelliFlo pump, instead of an old one. I also like the fact that that my pool stays skimmer all the time. At that speed, the pump is so quiet that you can't even tell the pump is running.

There is no right way here.. It is whatever works best for you.

Thanks,

Jim R.

 

[dcsmith]

dc,

A lot of people run their pumps 24/7.. It is just a difference in pool philosophy. You should do whatever works best for you.

The downside to generating all the chlorine your pool needs over a short period of time is that the pool continues to consume FC even when the pump is off. That means when the pump shuts off you need enough FC reserve to last you until the pump comes one again. As long as you know that just before the cell starts generating chlorine again, that your FC is still at your target level, then running only 7 hours a day will work just fine. The key is to test your FC just before the cell starts to make chlorine again and not just after the cell shuts off for the day.

I personally like to run 24/7, as I am making a little chlorine all the time and skimming all the time. I run mostly at 1200 RPM, so running 24/7 costs me less than $20 a month in electricity. It would be even less if I had a new IntelliFlo pump, instead of an old one. I also like the fact that that my pool stays skimmer all the time. At that speed, the pump is so quiet that you can't even tell the pump is running.

There is no right way here.. It is whatever works best for you.

Thanks,

Jim R.

Yes, I have variable speed pumps. However, at 7 hours a day it still costs me $1.24 per day. At 1,200 RPM, do you know what your flow rate is? At 7 hours, I am close to a full turnover of pool water per day.

 

[Jimrahbe]

dc,

The idea that you have to "turn over" x amount of pool water each day is just a myth and not true.

You should run your pump to accomplish specific tasks that you want to do. In your case you need to run the pump fast enough and long enough to make the chlorine your pool needs each day. I run at 1200, but I see you have heater so you would have to run at 1500 RPM or so. Then of course you will need to run your IFCS... I suspect that will take 2800 to 3200 RPM.

I never run anything based on Flow. I base it on what speed I need to accomplish the task I need to get done. In my case I need 1100 RPM to close the SWCG flow switch, plus a 100 more for insurance). I have no clue what that flow rate is and I don't care. It could be .1 turnovers or 100 turnovers, it does not matter to me.

In my tiny mind, you always want to run as slow as you can, and still close the flow switch. And then only increase the speed to do other things like run a water feature, use the heater, or IFCS and then only for the time it takes to get the job done.

Again, it is just one way to do it. My way is certainly not the only way, but it is the way that works best for me.

Thanks,

Jim R.

 

[Newdude]

The only issue DC is that a pool will lose 2-4 ppm a day from normal UV loss. If you are not producing FC for 20 hours, lose 4 ppm and only started at 4 or 4.5 ppm, it's only a matter of time until you have a swamp.

It's dancing the line too close. So raise the FC by following the LC side of the chart. The daily demand is lowering right now with shorter days, but you're in FL and it will still be moderately high for a while. Once the FC is raised, you'll probably be able to maintain it running the same schedule you are using. It won't cost much more than the initial gallon (?) to raise the FC.

FC does burn off as a % of the CYA, but at lower levels its not really noticeable. At SWG SLAM levels in the 20s, it becomes very noticeable, but the daily loss difference between 5 and 8 won't be much.