I drained approx 2/3 of my water and my CYA is still [email protected] 110!

Jayo

Well-known member
Dec 28, 2014
52
Heath, TX
I think my plan today is this:
Do the diluted water CYA test
Depending on results, I may drain some more water. (I'm expecting a very high reading)
Then chemicals...BUT I need help with the order in which to add them.
 

Jayo

Well-known member
Dec 28, 2014
52
Heath, TX
New Test Results: 10:30 am | Pool 83 degrees | Air 82 degrees

FC = .5 (CC = 0, TC = .5) (yesterday = 1.0)
pH = 7.5 (same)
TA = 90 (yesterday = 100
CH = 425 (yesterday = 450)
CYA = 120 (used 50/50 pool/tap water, doubled result) (yesterday = ? 110)
CSI = -0.10 (yesterday = 0.07)

I guess I'm glad the CYA isn't higher as I thought it would be. Is CYA stored in the plaster and pipes?

Also, I just want to thank you all for your help with this. I really appreciate it!!

Edited to add:

I have Blue Whale Shock Chlorinator / 12.5% sodium hypochlorite

Am I aiming for the FC at 11 - 13 in this chart?
CYA (Stabilizer)Minimum FCTarget FCSLAM

20*23-510
3024-612
4035-716
5046-820
6057-924
70*58-1028
80*69-1131
90*710-1235
100*811-1339
 
Last edited:

Rossterman

Well-known member
Jun 5, 2016
509
Martinez, CA
As said before your cya was probably off the charts. since you didn’t do the dilution test before there is no way to verify. That being said, you likely need another water exchange to get in a manageable range.
 

Jeff J.

Well-known member
Aug 6, 2019
221
Staten Island NY
New Test Results: 10:30 am | Pool 83 degrees | Air 82 degrees

FC = .5 (CC = 0, TC = .5) (yesterday = 1.0)
pH = 7.5 (same)
TA = 90 (yesterday = 100
CH = 425 (yesterday = 450)
CYA = 120 (used 50/50 pool/tap water, doubled result) (yesterday = ? 110)
CSI = -0.10 (yesterday = 0.07)

I guess I'm glad the CYA isn't higher as I thought it would be. Is CYA stored in the plaster and pipes?

Also, I just want to thank you all for your help with this. I really appreciate it!!

Edited to add:

I have Blue Whale Shock Chlorinator / 12.5% sodium hypochlorite

Am I aiming for the FC at 11 - 13 in this chart?
CYA (Stabilizer)Minimum FCTarget FCSLAM

20*23-510
3024-612
4035-716
5046-820
6057-924
70*58-1028
80*69-1131
90*710-1235
100*811-1339
New Test Results: 10:30 am | Pool 83 degrees | Air 82 degrees

FC = .5 (CC = 0, TC = .5) (yesterday = 1.0)
pH = 7.5 (same)
TA = 90 (yesterday = 100
CH = 425 (yesterday = 450)
CYA = 120 (used 50/50 pool/tap water, doubled result) (yesterday = ? 110)
CSI = -0.10 (yesterday = 0.07)

I guess I'm glad the CYA isn't higher as I thought it would be. Is CYA stored in the plaster and pipes?

Also, I just want to thank you all for your help with this. I really appreciate it!!

Edited to add:

I have Blue Whale Shock Chlorinator / 12.5% sodium hypochlorite

Am I aiming for the FC at 11 - 13 in this chart?
CYA (Stabilizer)Minimum FCTarget FCSLAM

20*23-510
3024-612
4035-716
5046-820
6057-924
70*58-1028
80*69-1131
90*710-1235
100*811-1339
I'm guessing 13-15, with a minimum of 10, extrapolating from the rest of the chart.
 

Jayo

Well-known member
Dec 28, 2014
52
Heath, TX
We can help you with adding Chemicals. Retest your CYA and post a current battery of tests and we can go from there.
What do you suggest for chemicals/amounts & order of application?

I might do some more draining since it's possible I underestimated the size of my pool by a few thousand gallons, and I see that it will be better to drain too much over too little (except for my water bill 😭)

I'm thinking I'd better get some chlorine into the pool before it turns green, then drain, right?

Or, I could wait to drain some more next month, keep the FC between 11-15 and continue to swim.

What are the dangers of swimming in high CYA?
 

DorsalSpine

Gold Supporter
Silver Supporter
Jul 8, 2013
706
Columbus, Ohio
I don't know enough to comment on extrapolating your FC level. I stick with the minimum of 8 and stay on the high side of the 11 - 13 FC range. You can swim in a pool as long as the FC is below the SLAM level.

I get your FC up ASAP and go from there. If you plan on exchanging water you will be wasting some FC but you don't want the pool to go green in the meantime.
 

Yev

Well-known member
Jul 29, 2014
546
Independence, KY
With the approved CYA test, any number over 100 is in question and should not be trusted. But let me do some math to help you. Lets say that your pool was 9000 gallons, and your CYA was 200. If you drained 2/3, down to 3000 gallons, those 3000 gallons would still have a CYA of 200. But if you add 600 gallons back to fill your pool, now the filled pool would be down to 67.

Do with a 2/3 drain, using the drain and then refill technique (and this is important to differentiate), the best you can do is to take your CYA down to 1/3 of its original value. And due to test accuracy, lets just say that you thought it was 200. It might have been 400 in reality.

So the fact that you are around 100 still seems fair, even if depressing.

When you say exchange, were you simultaneously draining and filling, simultaneously draining and filling with a tarp separating the new and old waters, or did you drain down, and then fill. I ask, because there is a huge difference in outcome.

The problem with simultaneously draining out water while adding in new water without a tarp separation, is that you are not only draining old water with high CYA, you are draining out new water as well. There are too many factors for me to do the math, but as a quick guess, simultaneous non-tarp actions would take my math example above, and rather than getting rid of 2/3 of your CYA, you might only get rid of 1/2 or 1/3, so your CYA might only go down from 200 to 100 or 133.

If you are going to use rain to exchange water, the best way to do this is like this. If you think that you will get 2" of rain in a week, drain your pool down 2" before any rain comes down. Then let the rain fill it back up. This provides the biggest bang for your buck so to speak.
 
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Jayo

Well-known member
Dec 28, 2014
52
Heath, TX
With these numbers, do I just need to add chlorine (2 gallons?)?

FC = .5 (CC = 0, TC = .5) (yesterday = 1.0)
pH = 7.5 (same)
TA = 90 (yesterday = 100
CH = 425 (yesterday = 450)
CYA = 120 (used 50/50 pool/tap water, doubled result) (yesterday = ? 110)
CSI = -0.10 (yesterday = 0.07)
I'm thinking if you want to get a good solid exchange heat the pool pretty well so the exchange will have a greater temperature split.
Now that's an interesting idea I've never heard mentioned...thanks.
 

Jayo

Well-known member
Dec 28, 2014
52
Heath, TX
With the approved CYA test, any number over 100 is in question and should not be trusted. But let me do some math to help you. Lets say that your pool was 9000 gallons, and your CYA was 200. If you drained 2/3, down to 3000 gallons, those 3000 gallons would still have a CYA of 200. But if you add 600 gallons back to fill your pool, now the filled pool would be down to 67.

Do with a 2/3 drain, using the drain and then refill technique (and this is important to differentiate), the best you can do is to take your CYA down to 1/3 of its original value. And due to test accuracy, lets just say that you thought it was 200. It might have been 400 in reality.

So the fact that you are around 100 still seems fair, even if depressing.

When you say exchange, were you simultaneously draining and filling, simultaneously draining and filling with a tarp separating the new and old waters, or did you drain down, and then fill. I ask, because there is a huge difference in outcome.

The problem with simultaneously draining out water while adding in new water without a tarp separation, is that you are not only draining old water with high CYA, you are draining out new water as well. There are too many factors for me to do the math, but as a quick guess, simultaneous non-tarp actions would take my math example above, and rather than getting rid of 2/3 of your CYA, you might only get rid of 1/2 or 1/3, so your CYA might only go down from 200 to 100 or 133.

If you are going to use rain to exchange water, the best way to do this is like this. If you think that you will get 2" of rain in a week, drain your pool down 2" before any rain comes down. Then let the rain fill it back up. This provides the biggest bang for your buck so to speak.
Great idea about the rain suggestion...thank you.

I simultaneously drained/filled using the recommended method on TFP.

I'm sure that the CYA was extremely high, probably 400 as you suggest it might have been, but at least now I'm fairly confident in the 120 reading from this morning (with the 50/50 test).

I read somewhere (maybe in this forum) that CYA is retained in the plaster and pipes...not sure if true or not, but wouldn't doubt it.

Thanks for your post.
 

Jayo

Well-known member
Dec 28, 2014
52
Heath, TX
I'm going to add 1 gallon of 12.5 liquid chlorine now, then test later in the evening. Will test all chemicals tomorrow.
 

Jeff J.

Well-known member
Aug 6, 2019
221
Staten Island NY
With these numbers, do I just need to add chlorine (2 gallons?)?

FC = .5 (CC = 0, TC = .5) (yesterday = 1.0)
pH = 7.5 (same)
TA = 90 (yesterday = 100
CH = 425 (yesterday = 450)
CYA = 120 (used 50/50 pool/tap water, doubled result) (yesterday = ? 110)
CSI = -0.10 (yesterday = 0.07)

Now that's an interesting idea I've never heard mentioned...thanks.
I would say yes.
 

mguzzy

Gold Supporter
Jul 8, 2015
2,336
OV, CA
I think my plan today is this:
Do the diluted water CYA test
Depending on results, I may drain some more water. (I'm expecting a very high reading)
Then chemicals...BUT I need help with the order in which to add them.
I'm not sure if you found the answer to this.. You can add chemicals in any order really the only rule of thumb is don't add MA and Cl and the same time, separate them by 30 min or so. Based on your numbers you only really need to add Cl and if you are planning on another water exchange your CH will go down by the same percentage as your CYA.

The efficiency of the no drain water exchange really depends on the difference in temperature of your fill water and your pool water because you are trying to take advantage of the physical properties of the two water sources to not mix much at different temps. If the temp of the fill water is close to that of the pool water their will likely be mixing at the boundary layer between the two. That's where the tarp method comes in since it imposes a physical boundary between the two.
 
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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,062
Laughlin, NV
That's where the tarp method comes in since it imposes a physical boundary between the two.
Do be ware of the risk involved in using a tarp. Children, pets, etc must be banned from the area. Constantly monitoring the pool area is required. We in general do not recommend this method due to the risks.