High CYA. How to test > 100. Chemical questions and going to re-plaster soon

[Rq120]

Hi all. I'm a noobie with the TFP method. I just got my TF-100 and I recently learned the connection between CYA and FC levels. Last year I would take a sample to the pool store weekly - every 2 weeks, but everything was always within range so I stopped that about a year ago. Last summer to now I was using chlorine pucks and test strips.
I have three questions.
1. I tested my CYA level today and it was under the 100 mark on the tube (so greater than 100). Is there a way to test this to know how much > 100 the level is?
2. We are going to re-plaster the pool in 6-8 weeks. So the water is going to be drained/re-filled then. Our city water is very expensive. We are also entering rainy season in FL so some of the water will naturally turn over. What do you think of stopping the pucks and letting the CYA level come down "naturally" until we re-plaster the pool as long as we don't have any algae issues.
3. Finally, CH was 525. I would look at the "Total Hardness" on the strips and it always around 250 so I thought I was good (until now). My CSI is 0.07 according to Pool Math. Would it be ok to let this ride until we drain the pool for re-plaster? I think I have read where it should be ok because of the CSI, but I want to make sure. Also, not noticing any visible scaling issues.

Chems today for complete picture:
FC: 6 (added LC today to get to CYA/FC goal)
TC: 0.5 (maybe less. One drop turned it back to clear)
pH: 7.4
TA: 100
CH: 525
CYA: > 100
CSI: 0.07

 

[mknauss]

Welcome to the forum!
If you are going to replaster in a couple months, I doubt it is worth doing much of anything different than what you are doing. If you would like to check your actual level of CYA, follow this:
Mix 50% pool water with 50% tap water. Use this mixed sample as your test water. Multiply the result by 2 for your CYA level.
CH is high due to either high CH fill water or the use of Cal Hypo 'shock'.
I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.

 

[mknauss]

Also - CYA does not 'go away' that easily. To lower it, you must physically remove the water in the pool and replace it with fresh water. That will happen with the replaster.

 

[Rq120]

Thanks. This is what I was hoping to hear. I retested my CYA using a diluted sample and the CYA is about 140. So twice what it should be. I'll keep a close eye on everything and drain some if I need. They may re-plaster as soon as 4 weeks. We are getting pavers done at the same time so it depends on how fast those come in.
CH - hmm, I'll have to test my water source. This will be helpful anyway with the re-plaster. I've only ever used the chlorine pucks, yellow out bag, and liquid chlorine in my pool. I've never shocked it any other chemicals. I know I'll have to manage that closely with the new plaster.

 

[Tonic1080]

Mix 50% pool water with 50% tap water. Use this mixed sample as your test water. Multiply the result by 2 for your CYA level.

Excellent and simple solutions. Simple enough I feel silly not thinking of it myself. Thanks!