Does anybody know of a way to test CYA below 10ppm? The lowest visual test tube I can find is 20ppm.
Thanks,
Tim
Thanks,
Tim
CYA and low level testing
- Thread starter Kingston331gt
- Start date
- Jun 22, 2014
- 47,854
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Tim, I'm not sure there is an accurate/reliable at-home way to do so. Maybe @JoyfulNoise can validate. Can you tell us why you are trying to test for such a low level?
There isn't a reliable one available for pool testing. Yes, it is possible, but we are talking laboratory style tests.
Since the test is accurate to within 10 ppm trying to gauge it below 20 is unnecessary. "It's 10, so that means it is somewhere between 0 and 20" is no different than when the test shows "<20" as a result. Anything less than 10 ppm CYA is virtually unnoticeable and one should always be mindful of not overshoot CYA additions anyway, so this limitation of the test is of virtually no consequence. There are other more consequential limitations of the melamine-based CYA test, but it is the best option available at this time.
Since the test is accurate to within 10 ppm trying to gauge it below 20 is unnecessary. "It's 10, so that means it is somewhere between 0 and 20" is no different than when the test shows "<20" as a result. Anything less than 10 ppm CYA is virtually unnoticeable and one should always be mindful of not overshoot CYA additions anyway, so this limitation of the test is of virtually no consequence. There are other more consequential limitations of the melamine-based CYA test, but it is the best option available at this time.
I have an autocover on my pool as well as an intellichem controller for PH and the SWG. ORP readings get jacked when CYA is higher than needed- which keeps the SWG making FC when not needed. With the autocover, the pool is treated mostly like an "indoor" pool as it is covered a lot of the time and not susceptible to UV rays.
When the pool cover is open, a CYA concentration of 3~6ppm keeps the half life of FC to about 4 hours which is perfect from opening to closing and still maintaining proper sanitization of just under 1ppm at the end of the day when I start at 3ppm, and the regenerative capacity of the IC40 cell is just over 1lb of 100% cl per 24h -but it only runs for 12~18 hours.
I had it perfect last year based by dosing CYA by mass and gallons, but this year I have some residual and need to know how much to add after draining some water for winterization.
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- Jun 22, 2014
- 47,854
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Well, hat's-off to you for analyzing your particular situation and making adjustments based on your auto-cover.
I'm not a numbers-cruncher like @Donldson or @JoyfulNoise, but it sounds as if you are utilizing your cover to run a very low CYA and FC ratio. Similar to an indoor pool, a nice concept, but even with an indoor pool we recommend a CYA of about 20 or so just for the buffering protection against the chlorine. In your case, I'm not sure if there are any consequences to consider which is why I tagged those two to see if they have thought or two. Hang tight for more validation.Thanks Tex - The higher CYA has more of an impact on ORP which is what the intellichem uses to turn on the SWCG. The more CYA, the lower the ORP even though FC can be super high. CYA of 20 triggered teh INtellichem to keep FC about 4.6ppm within an orp of 680, and CYA @30 kept the ORP under 600 even though FC was 6+. The intellichem is awesome and my SLI is usually within a few thousands of 0...just need to get it dialed in again this year. I attached a PDF of some science of relationship of CYA/ORP/FC that I validated in real world pool applications if anybody is interested.
Hootz
Bronze Supporter
- Feb 5, 2018
- 374
- Pool Size
- 24000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
Most of the data in this paper is based on a constant FC of 1.5.....the results show that as the cya numbers increase the effectiveness of the chlorine is reduced while remaining a constant 1.5 That may very well explain why our method is to significantly increase FC levels as the CYA levels rise. What are your average FC levels when your system is dialed in? Your intellichem system has me curious.
3~3.2ppm of FC when I open the cover. Keeping FC in the neighborhood of 3ppm, and CYA of 3 (or so) gives my FC a halflife of about 4 hours in full sun. That means, when i start at 3.2, after four hours my FC is 1.6, after four more hours, my FC is .8. This isn't just theoretical, this is measurable, repeatable and even predictable in my application. ORP during these times goes from 730 to 650, but this changes with bather load and is equally an art as it is science. The SWCG kicks on from the Intiichem at an ORP of 720, so it is working to keep it sanitied and ORP in check while the cover is open. the IC40 cell is rated at .35lbs of 100% chlorine gas in that same 8 hours. FC recovery to go back to 3.2 when the cover is closed, is about 8 hours - 4 hours in the evening and 4 hours in the am.
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Thanks, Kingston. Nice to see someone out there with the same equipment seriously working on making intellichem, SWCG, and ORP work. I got hosed by my PB who boosted CYA to 50 when starting the pool (I didn't know any better then) so my intellichem has had very difficult issues with ORP to FC ratio.
I've been trying to decide if I should drain to get CYA down to below 30, no really knowing how much it might help. Now that it coming on summer I'm hoping the sun and heat will degrade the CYA.
It encouraging to read about your "laboratory and "experimental results".
I've been trying to decide if I should drain to get CYA down to below 30, no really knowing how much it might help. Now that it coming on summer I'm hoping the sun and heat will degrade the CYA.
It encouraging to read about your "laboratory and "experimental results".
typo - .8 not .08. 4 drops of dpd reagent. Thanks for catching that - I will edit the post.
I spent the better part of 3 years researching, learning, testing, retesting and trial an error how to get this all to work CYA and TDS really impact ORP. Reducing what you put in the water, and how you "condition" or "stabilize" both have a big impact. There is no "set it here and forget it" with these systems. PM me if you want some help - PB's (and Pentair support) are pretty useless when it comes to helping with these and there is some help here - there used to be a dedicated Intellichem section here I think - but have not looked in a while.
Nice work! You are one of only a couple who seemed to have gleaned actionable/useful knowledge from the ORP readings. I know this question is NOT the route or solution that you found worked for you, but it is an answer that I keep trying to discern from every ORP post that I read...
Do you think there is any use for ORP measurement in a system with CYA in the 30+ range? I know this pushes the ORP readings very low, your data shows that...but might there still be distinguishable/repeatable differences in ORP readings for free chlorine in ranges from 0<—>8ppm?
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Yes, absolutely, I think so. My CYA is currently 50. My high ORP before sunrise was 623, my low this afternoon is 597. FC checked this AM in full sun was 6ppm. If I watch the highs and lows I can tell pretty much where my FC is. Fortunately its mostly sunny here in AZ so the diurnal cycle of the ORP is mostly uninterrupted.
My biggest problem isn't with ORP, its with the ORP suppression I see when the IC40 chlorinator is on versus when its off. This is I'm told due to hydrogen production affecting the ORP probe. In the winter when the chlorinator is off for a couple of days, the ORP can reach very high levels, 780+. When the chlorinator is turned on it can drop 150mV in half an hour. That's confounding to using closed loop control of the IC40 based on the ORP value. I've taken to dosing chlorinator based on time rather than to an ORP setpoint. I then set a high ORP value that will turn off the chlorinator is if it reached.
Not the elegant idea of using ORP but it is working right now. We'll see as it gets hotter and even sunnier.
I'm waiting for my CYA to drop from 50 to 30 but its stubborn. The grand kids swimming and jumping around splashing might start to help some.
Scott...thanks for the reply...and Hello Neighbor!...we are in the same neck of the woods!
Kingston, let me know if I am butting into your thread, but there is almost no discussion regarding ORP on these forums for good reason: there are few proponents and even fewer success stories. Like yourself, i like to get into details and ORP is something I really want to investigate/try, partly just for the challenge. But I have not had much inspiration for an attempt, and this is one of those threads that gives me the itch to move forward, haha.
So Scott’s reply has given me some hope. It sounds like even though the ORP readings are much lower and compressed (due to high CYA), there possibly are distinguishing differences between high and low free chlorine readings. It also sounds like there are many other factors in determining this: water temp, ph equivalence, CYA levels, etc.
My eventual plan is not necessarily to use ORP to control chlorine dosing...it would be more to generate warnings if free chlorine levels look completely out of whack. Initially I would be just monitoring all the various factors to see if I could discern such patterns. My control/monitoring/sampling system is flexible...given time and effort. In any case this would be project that probably would not start until next summer. Is it worth an attempt? I would have to buy and install ph and ORP probes.
Scott, it’s going to take a lot of splashing to get your pool down to CYA=30...sounds like about 40% water replacement. I don’t think you will get there before the end of the summer...You might want to just bite the bullet and drain? Also a question...can you just move your ORP sample valve to “before” your SWG to avoid some of the issues you are having?
Kingston, let me know if I am butting into your thread, but there is almost no discussion regarding ORP on these forums for good reason: there are few proponents and even fewer success stories. Like yourself, i like to get into details and ORP is something I really want to investigate/try, partly just for the challenge. But I have not had much inspiration for an attempt, and this is one of those threads that gives me the itch to move forward, haha.
So Scott’s reply has given me some hope. It sounds like even though the ORP readings are much lower and compressed (due to high CYA), there possibly are distinguishing differences between high and low free chlorine readings. It also sounds like there are many other factors in determining this: water temp, ph equivalence, CYA levels, etc.
My eventual plan is not necessarily to use ORP to control chlorine dosing...it would be more to generate warnings if free chlorine levels look completely out of whack. Initially I would be just monitoring all the various factors to see if I could discern such patterns. My control/monitoring/sampling system is flexible...given time and effort. In any case this would be project that probably would not start until next summer. Is it worth an attempt? I would have to buy and install ph and ORP probes.
Scott, it’s going to take a lot of splashing to get your pool down to CYA=30...sounds like about 40% water replacement. I don’t think you will get there before the end of the summer...You might want to just bite the bullet and drain? Also a question...can you just move your ORP sample valve to “before” your SWG to avoid some of the issues you are having?
jonpcar - I didn't even notice the Gilbert AZ. Hi!
I actually just got back in from testing CYA this morning to double check where I'm at. I first did the 50ppm reference fluid I have in the backyard per the standard sun to the back, waist high, glance method to re-calibrate my eye. Then I did my water and I'm gonna say I'm down to 40 now. Only took 7 months. I've been seeing less ORP range from day to night and this may explain that. I also think the warmer water now (pool temp 85) the hydrogen gas produced by the cell may not dissolve in the water as well or leave it faster? Although I'm excited to see what happens when I reach the 30ppm level, I really don't want to drain now that we are swimming a lot and i'm having adequate control over FC.
You're right, ORP is very dependent on pH for one. With the intellichem keeping my pH steady at 7.6 +/-.05 or so, that variable is largely eliminated. If your pH is going to move a lot, I don't think you could use ORP to dose chlorine directly. ORP would just have another pH caused cycle on top of the day/night cycle. I think one would go crazy trying.
I definitely think ORP can tell you if something major is up. I noticed through the winter when the chlorinator was off for days at a time, the ORP would oscillate day to night making slowly declining highs and lows. When the FC dropped to about 4-5, the ORP would drop rapidly from the 600-700's into the 500's. It didn't seem linear, more like a cliff. This always told me that the FC was getting pretty low. I was also noticing that ORP will tell you if a bunch of biologics blows into your pool. You can see a downward blip.
My flow cell where the ORP and pH probes reside inlet is plumbed between the pump and the filter. The cell is after the heater right before distribution to the pool so theoretically I shouldn't get any direct flow from chlorinated water into the cell.
I actually just got back in from testing CYA this morning to double check where I'm at. I first did the 50ppm reference fluid I have in the backyard per the standard sun to the back, waist high, glance method to re-calibrate my eye. Then I did my water and I'm gonna say I'm down to 40 now. Only took 7 months. I've been seeing less ORP range from day to night and this may explain that. I also think the warmer water now (pool temp 85) the hydrogen gas produced by the cell may not dissolve in the water as well or leave it faster? Although I'm excited to see what happens when I reach the 30ppm level, I really don't want to drain now that we are swimming a lot and i'm having adequate control over FC.
You're right, ORP is very dependent on pH for one. With the intellichem keeping my pH steady at 7.6 +/-.05 or so, that variable is largely eliminated. If your pH is going to move a lot, I don't think you could use ORP to dose chlorine directly. ORP would just have another pH caused cycle on top of the day/night cycle. I think one would go crazy trying.
I definitely think ORP can tell you if something major is up. I noticed through the winter when the chlorinator was off for days at a time, the ORP would oscillate day to night making slowly declining highs and lows. When the FC dropped to about 4-5, the ORP would drop rapidly from the 600-700's into the 500's. It didn't seem linear, more like a cliff. This always told me that the FC was getting pretty low. I was also noticing that ORP will tell you if a bunch of biologics blows into your pool. You can see a downward blip.
My flow cell where the ORP and pH probes reside inlet is plumbed between the pump and the filter. The cell is after the heater right before distribution to the pool so theoretically I shouldn't get any direct flow from chlorinated water into the cell.
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