When can I swim again after shocking?

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J

Jonatay

0
Jun 14, 2018
22
Fort Worth, TX
Here are my latest results after shocking my pool with 10% liquid chlorine last night.

FC = 10
CC = 0
pH = 7.6
TA = 130
CH = 210
CYA = 130

Is FC at 10 too high for us to swim? With the current CYA levels, what FC range do we need to maintain?
 
:wave: Welcome to TFP!

well actually your FC is almost too low given how high your CYA is. Check out the [FC/CYA][/FC/CYA] and you will find that your cya as well above are recommended levels. You can enter your values in PoolMath and it will tell you how high you should be maintaining your chlorine.
 
So I’m seeing we should be at 14-16 FC. What is confusing me are some articles stating that 5 and above are unsafe for swimming. But if I understand correctly, given my current CYA, FC maintained between 14-16 is recommended. Is that correct?
 
Jonatay said:
So I’m seeing we should be at 14-16 FC. What is confusing me are some articles stating that 5 and above are unsafe for swimming. But if I understand correctly, given my current CYA, FC maintained between 14-16 is recommended. Is that correct?
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Those articles don't account for the relationship of CYA to FC.

You really should get your CYA down to around 30 if you don't have a SWG. That will reduce your CL need. It will require a major drain and dilution of your pool water.

And stop using pucks and other solid chemicals that contain CYA and got your pool to this level.
 
Yes, I was using pucks, but recently switched to liquid chlorine. I had also added shock a few weeks ago that I didn’t realize also increased my CYA. Since then, I’ve read a lot about staying away from pucks and pH Up/Down. I used pH up several times when mine dropped to below 6.8. I then aerated for 2 weeks with no improvement. Finally added a box of Borax and saw immediate improvement. Now I keep on hand 10% liquid chlorine, muriatic acid, borax, baking soda, and calcium chloride. I’ve got 25lbs of pucks I’ll sell now.

I spoke with our pool builder yesterday and they seemed to think that CYA will decrease over the summer as long as I quit using the pucks.
Thank you for your help! I just added 88oz of liquid chlorine to get me up to 16 FC.
 
Jonatay said:
I spoke with our pool builder yesterday and they seemed to think that CYA will decrease over the summer as long as I quit using the pucks.
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It will take years for your CYA to drop from 130 to 30 naturally.
 
Firstly, welcome to TFP!

Jonatay said:
I spoke with our pool builder yesterday and they seemed to think that CYA will decrease over the summer as long as I quit using the pucks.
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Pool builders are good at building pools, unfortunately their chemistry knowledge is often rather lacking.

Natural degredation of CYA is about 5 ppm per month, maybe a bit more if the water is quite warm. So unless summer lasts over a year your CYA will not drop to a reasonable level over the summer. Also keep in mind that you cannot accurately test pH with your FC above 10. It would be well to consider doing at least a 25% replacement to get your CYA down below 100.

Which reminds me, did you get your 130 reading by the dilution test or by guessing? If the former then good, but if the latter you should remember that the scale is logarithmic, the space between the lines decreases as you go up, and your level could be higher than you might think.
 
Donldson said:
Firstly, welcome to TFP!


Pool builders are good at building pools, unfortunately their chemistry knowledge is often rather lacking.

Natural degredation of CYA is about 5 ppm per month, maybe a bit more if the water is quite warm. So unless summer lasts over a year your CYA will not drop to a reasonable level over the summer. Also keep in mind that you cannot accurately test pH with your FC above 10. It would be well to consider doing at least a 25% replacement to get your CYA down below 100.

Which reminds me, did you get your 130 reading by the dilution test or by guessing? If the former then good, but if the latter you should remember that the scale is logarithmic, the space between the lines decreases as you go up, and your level could be higher than you might think.
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I’m not opposed to a partial drain. It only cost me $50 to fill my pool after it was built at the end of last summer. What I’m not sure of is how to go about it. Do I use the pump somehow to pump it out? Do I siphon it out with a water hose? I know I have 3 valves before the water enters the pump, so maybe I do something there. Since I’m a new pool owner, I really don’t know.
 

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Jonatay said:
Interesting...Last week I was at 140. Not sure if it was rain, aeration, evaporation, or a combo of those, but it has decreased in 7 days.
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CYA testing is very subjective. A variability of 10 is within test to test differences.

How are you reading 130 or 140 as CYA test cylinders don't have markings that high? Are you diluting by 1/2 and doubling the result?
 
ajw22 said:
CYA testing is very subjective. A variability of 10 is within test to test differences.

How are you reading 130 or 140 as CYA test cylinders don't have markings that high? Are you diluting by 1/2 and doubling the result?
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Good point! It does only go up to 100. I had marked last week’s results with tape last week. This week the line moved up, so you’re absolutely right that I am guessing on the actual reading.
 
Jonatay said:
Do I use the pump somehow to pump it out? Do I siphon it out with a water hose? .
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Either could work. You can rent a pump or buy a submersible pump.

You can't use your pool pump since it will not pick up water once the water is below your skimmers.

Folks here can describe how you can pump from one end of the pool while filling from a hose in the other end of the pool. Which end you set it up with depends on the temperature of your pool water versus fill water.

- - - Updated - - -

Jonatay said:
Good point! It does only go up to 100. I had marked last week’s results with tape last week. This week the line moved up, so you’re absolutely right that I am guessing on the actual reading.
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Retest diluting your sample water with 50% pool water and 50% tap water, then add reagent. Double the CYA number you get.
 
You can exchange some water without draining.

If you place a low volume sub pump in the deep end and pull water from there while adding water in the shallow end you can do a fairly efficient exchange. That is assuming the water you are filling with is the same temperature or warmer than your pool water. If your fill water is much cooler than your pool water, then switch it. Add the water to the deep end (hose on bottom) and pull water from the top step.

The location of the pump and fill hose may change if you have salt water, high calcium, etc.
In my pool, with saltwater and high calcium when I drain, I put the pump in the deep end and hose in shallow end. The water in the pool weighs more per unit volume than the fill water from the hose.

Be sure to balance the water out and water in so the pool level stays the same. Also be sure your pool pump is disabled during this process. Once started do not stop until you have exchanged the amount of water you wish.
 
mknauss said:
You can exchange some water without draining.

If you place a low volume sub pump in the deep end and pull water from there while adding water in the shallow end you can do a fairly efficient exchange. That is assuming the water you are filling with is the same temperature or warmer than your pool water. If your fill water is much cooler than your pool water, then switch it. Add the water to the deep end (hose on bottom) and pull water from the top step.

The location of the pump and fill hose may change if you have salt water, high calcium, etc.
In my pool, with saltwater and high calcium when I drain, I put the pump in the deep end and hose in shallow end. The water in the pool weighs more per unit volume than the fill water from the hose.

Be sure to balance the water out and water in so the pool level stays the same. Also be sure your pool pump is disabled during this process. Once started do not stop until you have exchanged the amount of water you wish.
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water out of the hose is 84°. Pool water is currently 88°

Should I put the pump in the deep end?
 
Your tests you showed earlier in the thread showed pretty low calcium and this is not a saltwater pool.

So, I would suggest you add the water to the deep end and pump from the shallow end, preferably a top step.

Your fill water is colder and thus should lay on the bottom of the pool.

It will not be a perfect exchange. But should get your down in the mid double digits of CYA if you run the exchange long enough.
 

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