Proper Reading of CYA Levels?

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Steve-D

Steve-D

Well-known member
Jul 10, 2020
149
SW Boston Suburbs
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
We have a new pool that is not yet "officially" done as the installers need to come back and add salt and program the control panel. We have been told that it is still swimmable while the plaster finishes its curing process so In the meantime we have been maintaining Chlorine manually. That has been a struggle as we started with 0 CYA so CL dropped to about zero daily. Once CYA hit 40 the CL level became more stable but we hadn't yet worked out how much liquid CL (12.5%) to add and now its on the high side (5.0 FC / 0 CC) and we have been waiting for it to slowly come down to the 1.5-2.5 range (target per installers).

My question is how well I'm reading CYA levels with the "see the black dot" test? How much (if any) of a shadow of the dot marks the point at which I note my reading? and how much would one expect CYA to change with 300(ish) gallons of well water added to a 20,000 gallon Gunite pool?

Gradually adding (sock method) 4 lbs of stabilizer took a day for CYA to go from 0-20, another day to hit 25 and another day (5/17) to hit 40. I (more aggressively) added another 4lbs of stabilizer and saw CYA move up to 50 on 5/18 and top out at 60 on 5/20. Our installer came by and said we needed to add about an inch of water (approx 300 gal) and when I next tested the CYA level read as 45. I tested again today and got the same (45) reading. Would 300 gallons of well water cause that drop? Am I not correctly/consistently reading the level? Some combination of the 2?

I also saw my Calcium Hardness (CH) level go from a previously stable 210 on 5/17 to 240 on 5/22 (where it remains) without any treatments beyond that 300 gallons of well water. Is that change in CH due to my well water and where to people go to test their water for that? If my well water is bumping up the CH then how to I keep the water level high enough without eventually hitting the upper Calcium Hardness limits?

Current tests (5/24. 10:30 AM, with water temp @ 70F:
FC 5.0 / CC 0.0
pH 7.6
TA 100
CH 240
CYA 45
 
Steve-D said:
My question is how well I'm reading CYA levels with the "see the black dot" test? How much (if any) of a shadow of the dot marks the point at which I note my reading? and how much would one expect CYA to change with 300(ish) gallons of well water added to a 20,000 gallon Gunite pool?
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That would cause about 1.5% dilution. Not enough to be detectable.
Steve-D said:
Gradually adding (sock method) 4 lbs of stabilizer took a day for CYA to go from 0-20, another day to hit 25 and another day (5/17) to hit 40. I (more aggressively) added another 4lbs of stabilizer and saw CYA move up to 50 on 5/18 and top out at 60 on 5/20. Our installer came by and said we needed to add about an inch of water (approx 300 gal) and when I next tested the CYA level read as 45. I tested again today and got the same (45) reading. Would 300 gallons of well water cause that drop? Am I not correctly/consistently reading the level? Some combination of the 2?
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Few points here.
1 - The CYA scale is not linear. You cannot read between lines and say 45. If it is past 40 then it is 50.
2 - The CYA test is a bit more subjective than everyone would like it to be. Try filling the tube until each mark and glance inside. If you can see the dot at first glance then proceed to the next mark... lighting can also be an issue. Make sure you are in a well lit area, but not in direct sunlight.
Steve-D said:
I also saw my Calcium Hardness (CH) level go from a previously stable 210 on 5/17 to 240 on 5/22 (where it remains) without any treatments beyond that 300 gallons of well water. Is that change in CH due to my well water and where to people go to test their water for that? If my well water is bumping up the CH then how to I keep the water level high enough without eventually hitting the upper Calcium Hardness limits?
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The increase in CH is more likely to be from your new Plaster than from your fill water. Your CH is low for plaster and you need to get it to Recommended Levels
If you are concerned about CH on your well water just get a sample and test it.
 
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Thank you @AK- .
I Tested our tap (well) water for Calcium Hardness and it looks to be about 240-250. Reading from Installer's (Stone Edge Design) "New Plaster Startup Procedure" from their New Customer booklet:
First day procedure after the pool is full:
Day 1-14: Test the water for pH, calcium hardness, alkalinity and irons.
1. Add stain preventer (Iron Out, Pool Magnet)
2. High Alkalinity should be adjusted to 80ppm using pre-diluted
Muriatic Acid (31-33% Hydrochloric acid). Pre-dilute acid by adding
it to a five gallon bucket of pool water. Low Alkalinity should be
adjusted to 80ppm with sodium bicarbonate (baking soda).
3. PH should be reduced to 7.2 - 7.6 by adding pre-diluted Muriatic
Acid if the alkalinity is already 80-100ppm.
4. Test water daily for the first two weeks (14 days)
Continue with these instructions and tips:

Day 1-14: • Lightly brush your new surface twice daily, for the first two weeks with a nylon pool brush, starting at the shallow end moving towards the deep end. (Do not brush Pebble Finish until after 7 days)
Day 2: • Add calcium to increase calcium hardness to a minimum of 150ppm only once the alkalinity is adjusted to 80ppm and pH is stable between 7.2 – 7.6 (typically day 2) Caution: Adjustments requiring more than 20lbs of Calcium should be pre-diluted and added in 10lbs increments - morning and afternoon. Do not over shoot the desired level, high calcium levels can only be reduced by dilution.
Day 3: • Add pre-diluted chlorine last (after 48hrs) and raise levels gradually to achieve 1.5 to 3ppm, only after the pool water is balanced. Do not add salt for 28 days.
Day 4-28: • After the 7th day remove any plaster dust with a brush pool vacuum. • After the 4th day calcium levels should be adjusted slowly over the 28 day period……not to exceed 200ppm. • After the 4th day Cyanuric acid levels should be adjusted to 30-50ppm based on the primary sanitizer of the pool (predissolve & add through the skimmer)

After 28 days maintain pool at:
Total Alkalinity 80 to 120 ppm
Calcium Hardness 200 ppm
Cyanuric Acid 30 to 50 ppm
PH 7.2 to 7.6
Free Chlorine 1 to 3.0 ppm
Salt Level 2500 to 3500 ppm
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The installers are coming with Salt this week "by Friday" so we want to be within their recommended levels as much as we can by then and as for right now only the Chlorine level is off (too high). Once we are into the season and water chemistry requirements requirements are clarified as they related to the Installer's warranty we will be looking to ease into the TFP method. This is not our first pool but it IS our first in ground and non-vinyl liner pool so my wife will kill me if I stray too far from their guidance...at least at the outset.

As to CYA testing, I wonder if I'm just obsesseing about when the dot fully disappears and not being 100% consistent rather than checking at a first glance.
 
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OK...I'm still questioning how well I'm reading CYA. I've been recording it at 60 but I'm wondering if it really is closer to 40. I'm viewing in a well-lit bathroom with a white throw rug as the background and If I just fill to a line and do a quick glance I can see a shadow where the dot is at 60 and at 50 but less so @ 40. For a 20,000 gallon new filled-by-truck pool with 8 lbs (2 @ 4 lbs) bags of Clorox does 40 make more sense than 60 as a likely accurate reading? I have another 4lb bag I can add but I hate to put stuff in the pool that requires draining to adjust the numbers down...especially with a well. It would be nice if there was a less subjective CYA test that I could do at home.

I've been struggling to get the FC level right as it had been creeping up to a recent high of 12 ppm with the SWG running continuously, days of no sunshine and the pool covered so little chance to drop the FC. Now my FC is back down to 6.0 but I'm questioning my CYA reading and it is the difference between hitting my FC target or speeding up the pump to generate more FC again.

PH took a dive from yesterday (down to 7.0 from 7.5) , too, so I'm taking advantage of a windy day and adjusting one of my inflow jets to aerate the PH back up gradually. TA also dropped from 120 to 100. I welcome finding the balance for this new pool. I know it will come but it sure is a pain getting there for the first time.
 
Steve-D said:
It would be nice if there was a less subjective CYA test that I could do at home.
Click to expand...
There isn’t. If you glance at the bottom of the tube and don’t see the dot then that is your CYA . Trust your test results. No one likes the CYA test.

If you are afraid of overshooting go slow in 10 ppm increments (that is what I do with CYA).
 
Thank you both (@AK- & @Mdragger88 ). Before I came to know TFP when testing my 8000 gallon round above ground pool I obsessed between "dot is absolutely no longer visible" and "I can see a shadowy area where the spot is" and would consistently go with the obsessive (and inevitably higher) "absolutely gone" reading. Now that I am more fully aware of the CYA/FC relationship I'm trying to be more accurate with CYA.

Per "Pool Math" 8 lbs (128 oz) of stabilizer would raise CYA to about 48 so it seems reasonable to me that adding one 3" stabilized Cl puck and 5 oz of granular stabilized Cl in early May would increase CYA by only a marginal amount. Based on that should I trust my 50 ppm reading or might the other usual additions (some dry acid but now exclusively MA) boost CYA to what I read as 60 ppm?

The old above ground pool was just under 8000 gallons and I was on city water so partial draining and refilling was a manageable exercise. Now, however, its a salt pool and we have a well and its almost triple the volume so I don't want to put myself in a "you need to drain" situation if it can be avoided.
 
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Steve-D said:
Thank you, @Dirk !
Checking the Taylor site should have been a "Doh!" ... now I know.

A direct link to that Taylor page would be a very helpful addition to the Pool School "Cyanuric Acid" page.
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It is linked or at least the picture is in the notes section in the extended test directions

www.troublefreepool.com

CYA - Cyanuric Acid Test

Cyanuric Acid (CYA) is the chemical name for what is commonly referred to as Stabilizer … Read more…
www.troublefreepool.com www.troublefreepool.com
 
I think it wise to have your chemical levels exactly where the builder suggested, until they're gone. That way, there can be no warranty disputes. That said, once the pool is in your control, an FC of "1.5-2.5" is too low, way too low. Here's why.

Your CYA should eventually get to 70. That's the minimum we recommend for a SWG pool. Which means your target FC should be 5. Your minimum FC, the level you would never want to go below, is 3. "1.5-2.5" on a hot day is asking for trouble. So your current FC of 5 is not all that high. Like some others here, I "ignore" the TFP minimum FC and treat my recommended target FC of 5 as my minimum. I do whatever it takes to never let my pool get below 5. Because that's going to happen. A hot day. Perhaps a lapse in testing. A roudy bunch of kids that can't "hold it." Or a severe "bird strike." Maybe a thirsty varmint falls in and drowns. Or a combo of any of those and you have a perfect storm for your FC dropping a few notches in a matter of hours. If you treat your minimum as 5, and your FC inadvertently drops a few notches, you'll still have an FC of three and will likely be able to avoid any algae outbreaks. But if you target 5 and get a little lax regularly, letting it drop to 4 or 3, knowing that you're still at minimum FC or above, and then that perfect storm occurs, now those couple notches will put your FC down to 2 or 1, and boom, in one day you could be looking at an algae problem! Maintaining a minimum of 5 gives you a built-in "FC safety buffer."

Remember, you can safely swim in a pool with your FC at SLAM level, which in the case of 70 CYA would be in the mid 20s! An FC of 5 or 6, is perfectly fine.

It's just not worth the risk. Get your CYA up to 70, keep your FC at 5 or 6 or 7. If it drops to 4, treat that as a red alert event and use liquid chlorine to instantly get your FC back up to 6+. Always keep a gallon or two of liquid chlorine around for just that reason. And if you anticipate a big pool event, where your swimmer load will increase well above your norm, use liquid chlorine to bump your FC up a notch or two, just before your party. Like 6 or 7, or more if it's a big event. And then check your FC right after your party, and restore your FC to 6+. After a while you'll get a feel for how many extra people your pool can handle, vs when to "pre-bump" your FC level to accommodate a crowd.

That's how I do it, anyway...
 
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Thank you (again), @Dirk !

The PM for our installers is scheduled to be here this afternoon with a Pentair resource to get the heater running and to program the panel (which we expect will also enable our use of the ScreenLogic app). Once that's done we should have more finely tuned control of the pool and can get some automated schedules in place to manage the pump flow and FC generation.
 
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You'd think a pool builder would know everything there is to know about automation equipment and pool water chemistry. But they don't. It's a very common tale here at TFP. You have to keep them "satisfied" when it comes to the warranty, but other than that, trust your own water testing (NOT a pool store's) and trust TFP guidelines when it comes to maintaining your chemistry. My pool was a disaster before I took it away from "the pros" and started taking care of it myself, based on advice from TFP. You're in good hands here.

There are many here that can help you with the automation and SWG setup, too. Just ask...
 
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