New Pool Owner, Basic Questions

[brock.travis]

I just purchased a house that has a 13500 gal IG Gunite DE pool that hasn’t been maintained for about a month. I have a few questions around pool ownership in general and some specific to my pool. I’ve spend a few days doing as much research as possible but I still have some questions.

I took a water sample to the local pool store and got the readings below.
FAC = .5
pH = 7.6
TA = 100
CYA = 60
CH = 450

I was surprised that they did not include a reading for total chlorine. After all, don’t you need to know the total chorine to find the combined chlorine in order to shock it away?

Pool guy said my pool was mostly in balance with the exception of it needing a shock and I should drain 50% of the water to combat the hardness towards the end of the season.
He sold me Power Powder Pro (73% cal-hypo) with instructions to dump two pounds of it in the pool two days in a row. Doesn’t cal-hypo add calcium to the water? Shouldn’t I use bleach instead?

How did the pool guy determine the amount of chorine needed in order to shock the pool? This is probably my biggest question. I’m unable to calculate the amount of various products needed in order to shock. (Yes, I have looked at poolcalculator.com but I don't know what my target should be) I thought I remembered reading somewhere that you need 10ppm AC to convert 1ppm of CC. Is that right? If it is, then I would just need to find out how many ppm of CC I have and put 10x that amount of AC right?

EDIT: On a side note, I've looked at the "Chlorine / CYA Chart" but I'm unsure how to read it.

 

[JasonLion]

Welcome to TFP!

With CYA at 60, routine day to day FC levels should be 5 to 9 and shock level is 18 to 20.

Yes, cal-hypo adds calcium. It was silly of them to sell you that after telling you that your CH level was too high.

There is a good tutorial on using the Pool Calculator in Pool School.

I imagine that your CC level was zero, so they didn't bother writing it down, though it is also perfectly possible that they simply didn't bother testing your CC level.

The CCx10 rule is completely wrong and should be ignored. If there is obvious algae in the water or CC above 0.5 you should shock the pool as described in Pool School.

 

[Suziqzer]

Ok... so you got confusing information from the pool store... not unexpected. Drain part way and then add more calcium...

You were right in thinking Cal-Hypo does add calcium... so them suggesting to add that for shock was going to add to your high calcium.

I'm not sure what calculations the pool guy used to tell you how much to use to shock your pool. Looks like you know how many gallons your pool is ... so plug that into the pool calculator, then put in the values you know... including cya. At the bottom of that page you will see "Suggested Goal Levels" in yellow... select tfp and your other information. After you've entered all of your known information, look at the "Suggested FC Levels" in blue. It will tell you what your fc levels need to be and what shock level is.

You will also need to read the pool school ... How to shock your pool... http://www.troublefreepool.com/pool-school/shocking_your_pool.

Shocking is a process, not a chemical. Something the pool stores don't often tell you either.

 

[brock.travis]

So the only readings that come into place when calculating the amount of chemicals needed to shock is the current FC and the current CYA?

According to the pool calculator with all of my readings entered and my pool volume in place, to bring my FC from .5 to 24 (Shock FC according to the chart) would require 658oz of 6% bleach. Is that right? After the shock I should try to maintain 7ppm FC? That’s way over the recommended 4ppm the pool store recommended.

There is algae on the steps and the walls in some areas so I assume that CC is not zero. (I have not yet purchased a test kit)
The algae is mostly green with some areas that are black. I think some of the algae on the walls also has a yellowish color to it (if that’s even algae at all).
The pool is mostly clear. I can see the bottom just fine.

 

[brock.travis]

I'm not sure what calculations the pool guy used to tell you how much to use to shock your pool. Looks like you know how many gallons your pool is ... so plug that into the pool calculator, then put in the values you know... including cya. At the bottom of that page you will see "Suggested Goal Levels" in yellow... select tfp and your other information. After you've entered all of your known information, look at the "Suggested FC Levels" in blue. It will tell you what your fc levels need to be and what shock level is.

So should I be using the Shock FC (24) from the "Chlorine / CYA Chart" or the "Suggested FC Level Shock" (18) when setting my target FC in the calculator?

 

[JasonLion]

Either one, or something in between. Both levels work, the higher levels work more quickly.

 

[brock.travis]

isn't this chemistry? Shouldn't the numbers be more exact?
what about the questions in my second post?

 

[duraleigh]

After the shock I should try to maintain 7ppm FC?

You are missing that shocking a pool is NOT bringing it to shock value once. It is bringing the FC to shock value and holding it there constantly until your pool is crystal clear.

You should read "How to Shock Your Pool" up in Pool School.....trying to do it with one dose won't work.

 

[brock.travis]

After the shock I should try to maintain 7ppm FC?

You are missing that shocking a pool is NOT bringing it to shock value once. It is bringing the FC to shock value and holding it there constantly until your pool is crystal clear.

You should read "How to Shock Your Pool" up in Pool School.....trying to do it with one dose won't work.

Okay, so I should shock the pool according to the document in Pool School.
Each dose should be the 18ppm (by calculator) or 24ppm (by chart), right?

Where does the target FC of 7ppm come into play in my case? (according to the chart)

 

[duraleigh]

Where does the target FC of 7ppm come into play in my case?

It's the suggested value you can use to maintain your pool once you have finished the shock process.

You have finished the shock process when...
1. Your water is crystal clear.
2. You lose less than 1.0 FC during the FC overnight loss test
3. Your CC's test is .5 or less

Each dose should be the 18ppm (by calculator) or 24ppm (by chart), right?

No. Prior to adding your next dose, you test to see how much FC is remaining from the prior dose.

For example, you have 0 FC so you dose enough to put 24ppm in your pool. 6 hours later, you test again and this time your FC reads 10ppm....it has dropped by 14ppm You then add enough (14ppm) to return the FC to the suggested 24ppm.

You perform that test and add, test and add, test an add continually until the pool is clear and meets the criteria above. 3-4 times daily is most common.......more is fine. Once daily is not enough to be very effective.

 

[brock.travis]

Where does the target FC of 7ppm come into play in my case?

It's the suggested value you can use to maintain your pool once you have finished the shock process.

You have finished the shock process when...
1. Your water is crystal clear.
2. You lose less than 1.0 FC during the FC overnight loss test
3. Your CC's test is .5 or less

I wonder why the pool store recommends no more than 4ppm.

 

[zea3]

Hi Brock, welcome to TFP. Yes, pool care is a science but not an exact science. The values from the pool calculator and from the Chlorine/CYA chart do not always match up but they will work. There is a range that is effective is dependent on many variables, which is why you don't see things like all pools should have 1.5 ppm FC and 250 CH only. The exact value you need for shocking your pool is within the range represented by the chart and the pool calculator. Personally I prefer the pool calculator.

Now the reason the pool store is telling you something different is that most employees have not been trained to understand the CYA/chlorine relationship. They rely on training from their vendors who only look at the levels in an ideal pool. If you had a CYA of 30, then FC at 4 ppm would be just fine, but you don't, you have CYA of 60. If you try to maintain FC at 4 ppm you will probably develop algae. 4 ppm would be near the bottom of your acceptable daily range, but if you miss a day adding bleach the FC will drop too low. Miss 3 days in a row and you are in the beginning of an algae bloom. Remember, this is the same place that wanted you to drain water to lower CH and sell you cal-hypo which raises CH at the same time.

It would be nice if all pool store employees where trained experts but they are not. Most of them don't even own a pool.

edit: You and Dave type faster than I!

 

[aa62579]

Okay, so I should shock the pool according to the document in Pool School.
Each dose should be the 18ppm (by calculator) or 24ppm (by chart), right?

Where does the target FC of 7ppm come into play in my case? (according to the chart)

You need to get a good test kit because you have to be able to measure your FC and CC at high numbers.

You will add in the amount of bleach needed to get your FC up to 20 (I just picked an easy number in the middle). An hour later, retest, and add chlorine to bring back up to 20. You may have only dropped to 15 and need to add 5ppm, or you may have dropped to 10 and need to add 10ppm. You have to have a test kit to be able to keep measuring this. You will do this through out the shock process until you meet the three criteria duraleigh posted.

Once you meet ALL THREE of those, you are done with the shock process and you will now use the FC target of 7 each day. (Most people test in the evening or in the early morning - once per day)

 

[brock.travis]

Hi Brock, welcome to TFP. Yes, pool care is a science but not an exact science. The values from the pool calculator and from the Chlorine/CYA chart do not always match up but they will work. There is a range that is effective is dependent on many variables, which is why you don't see things like all pools should have 1.5 ppm FC and 250 CH only. The exact value you need for shocking your pool is within the range represented by the chart and the pool calculator. Personally I prefer the pool calculator.

Now the reason the pool store is telling you something different is that most employees have not been trained to understand the CYA/chlorine relationship. They rely on training from their vendors who only look at the levels in an ideal pool. If you had a CYA of 30, then FC at 4 ppm would be just fine, but you don't, you have CYA of 60. If you try to maintain FC at 4 ppm you will probably develop algae. 4 ppm would be near the bottom of your acceptable daily range, but if you miss a day adding bleach the FC will drop too low. Miss 3 days in a row and you are in the beginning of an algae bloom. Remember, this is the same place that wanted you to drain water to lower CH and sell you cal-hypo which raises CH at the same time.

It would be nice if all pool store employees where trained experts but they are not. Most of them don't even own a pool.

edit: You and Dave type faster than I!

Thanks for the clarification. Just a whole bunch of data I’m trying to absorb at once. I was incorrect in thinking it was an exact science (ones and zeros, right and wrong, yes and no) and that you actually have to ‘play’ with it. After all, it’s not a laboratory environment and time becomes a factor.
So what I will probably do is forgo the Cal-Hypo and get some bleach for this first shock process.
What levels of FC are acceptable to swim in? My wife is in a hurry to swim but the water just isn’t right yet.
Also, are there any products to lower calcium hardness or is draining the only solution?

You need to get a good test kit because you have to be able to measure your FC and CC at high numbers.

You will add in the amount of bleach needed to get your FC up to 20 (I just picked an easy number in the middle). An hour later, retest, and add chlorine to bring back up to 20. You may have only dropped to 15 and need to add 5ppm, or you may have dropped to 10 and need to add 10ppm. You have to have a test kit to be able to keep measuring this. You will do this through out the shock process until you meet the three criteria duraleigh posted.

Once you meet ALL THREE of those, you are done with the shock process and you will now use the FC target of 7 each day. (Most people test in the evening or in the early morning - once per day)

Thanks for dumbing down the process for me. That helped a lot.

 

[Suziqzer]

Before swimming, you'll want to go through the entire shock process and be sure you've passed all the tests there...
1) Get your water cleared
2) Maintain overnight w/o losing more than 1ppm
3) .5 or less CC

After you've passed all of those tests, it is safe to swim in anything under your shock value.