Rollercoaster pH

[KevinL]

Happy Thanksgiving, pool owners. Recently, my PH has been jumping up and down, even during a 24-hour period. Currently I've been adding chlorine and acid every 6 days. When I do, I usually target a pH of 7.8 because no one is currently using the pool and I find that it gets my LSI close to zero. Anyway, I added Cl and acid a couple of days ago, and just take a look at my pH over the past 24 hrs (photo attached). It's been going up and down like a yo-yo. Yes, it's shown some variability in the past but nothing like this. I'm wondering what's going on. Does anyone have some ideas?

PS - I added a little less than a pound of sodium carbonate at 9 pm last night to bring pH up some. You can see the pH reverse direction at that point.

Currently:
FC = 14 ppm
CC = 0 ppm
Temp = 62 F
pH = all over the map
TA = 90 ppm
CH = 390 ppm
CYA = 55 ppm

Thanks for any tips!

 

[Bperry]

Happy Thanksgiving, pool owners. Recently, my PH has been jumping up and down, even during a 24-hour period. Currently I've been adding chlorine and acid every 6 days. When I do, I usually target a pH of 7.8 because no one is currently using the pool and I find that it gets my LSI close to zero. Anyway, I added Cl and acid a couple of days ago, and just take a look at my pH over the past 24 hrs (photo attached). It's been going up and down like a yo-yo. Yes, it's shown some variability in the past but nothing like this. I'm wondering what's going on. Does anyone have some ideas?

PS - I added a little less than a pound of sodium carbonate at 9 pm last night to bring pH up some. You can see the pH reverse direction at that point.

Currently:
FC = 14 ppm
CC = 0 ppm
Temp = 62 F
pH = all over the map
TA = 90 ppm
CH = 390 ppm
CYA = 55 ppm

Thanks for any tips!

Assuming you’re using the Taylor test kit and not relying on ORP for automated dosing acid, adding sodium carbonate was not necessary. The pH will rise all by itself over time unless you are adding acid. And you can slow it down by letting your TA go down to about 50-60ppm.

Also note that some smarter than me TFP folks report that ORP measurement starts going wonky when CYA gets above ~30/40ppm.

 

[proavia]

What type of device/equipment are you using to get the display shown in your attached picture?
Your signature is severely lacking in detail. Manufactures and model numbers of all of your equipment will assist us in helping you without needing to ask.

How are you chlorinating?

What is the pH, TA and CH of your fill water (measured using your K-2006)?
How old are your test kit reagents? Do the bottles have expiration dates?

When doing the CYA test, if the result falls between two lines on the tube, round up. A CYA of 55ppm is rounded up to 60ppm.

Your latest PoolMath logs are from 5 months ago.

 

[KevinL]

Assuming you’re using the Taylor test kit and not relying on ORP for automated dosing acid, adding sodium carbonate was not necessary. The pH will rise all by itself over time unless you are adding acid. And you can slow it down by letting your TA go down to about 50-60ppm.

Also note that some smarter than me TFP folks report that ORP measurement starts going wonky when CYA gets above ~30/40ppm.

Thanks. Yes my sensor also measures ORP, but I don't really rely on it. I'm just concerned about my PH going all over the place.

 

[KevinL]

What type of device/equipment are you using to get the display shown in your attached picture?
Your signature is severely lacking in detail. Manufactures and model numbers of all of your equipment will assist us in helping you without needing to ask.

How are you chlorinating?

What is the pH, TA and CH of your fill water (measured using your K-2006)?
How old are your test kit reagents? Do the bottles have expiration dates?

When doing the CYA test, if the result falls between two lines on the tube, round up. A CYA of 55ppm is rounded up to 60ppm.

Your latest PoolMath logs are from 5 months ago.

I use the iopool Smart Water Monitor for the pH measurement.

I add liquid chlorine with the pump on, wait one hour, then add acid.

My test kit is about 5 months old.

Thanks, I knew about the CYA rounding rule. I just feel tempted to add 5 when it's not quite there.

I don't use PoolMath anymore. I use the Orenda calculator.

 

[Bperry]

Thanks. Yes my sensor also measures ORP, but I don't really rely on it. I'm just concerned about my PH going all over the place.

What’s your test kit say the pH is? The graph you showed doesn’t say much and I’d suspect the pH drop is not real because it doesn’t act like that unless you got a lot of low pH rain or have been adding acid.

 

[ajw22]

Any pH in the 7’s is fine. Your varying pH is not a concern.

Don’t micromanage the pH. PH is not stable. It drifts around with chemical additions and the environment.

Adding liquid chlorine will cause a temporary pH rise before pH drifts back down. Adding acid lowers your pH. While adding sodium carbonate will raise pH. So you are yo yoing your pH around more then necessary.

That amount of data and precision on the pH is unnecessary in a pool. You can do as you wish with your gadgets but they do not follow Trouble Free Pool methods.

Pool Care Basics Archives

Your one-stop shop for all things TFP to include: ABCs of Water Chemistry, Recommended Chemicals/Levels, Test Kits, Troubleshooting, and much more!

www.troublefreepool.com

 

[Dirk]

I use the iopool Smart Water Monitor for the pH measurement.

That's where I'd start. Test your pH with the Taylor reagent test and compare results to your gizmo. The Taylor test is far more reliable, and not subject to calibration errors, battery issues, electronic glitches, etc.

Sidebar: If you gave me a digital pH tester I wouldn't use it. Alongside my regular FC testing, pH takes an additional 30 seconds. I couldn't test digitally that fast, so why would I? The only legit reason to use a digital tester, IMO, is if your eyes have trouble making out the hues of the Taylor test.

And just to beat you up a bit more, you're straying from the TFP methods. Using other than recommended testing procedures, tracking with other than recommended methods. Which is totally fine, it's your pool. You gotta find what works for you. But we use one set of methods here, because they work and are virtually bulletproof. Torture tested for many, many years, by 100s of 1000s of members. These methods also facilitate our ability to help you. The more you stray, the more you're going to be on your own. I'm not saying we won't try to help you, I'm just saying that help will necessarily be limited.

 

[proavia]

Use your K-2006 and PoolMath when discussing issues here.
Adding in your Smart Pool Monitor and Orenda calculator just confuses the issue - especially when you don't mention them or show them in your signature.

TFP is based on accurate test results from one of the recommended test kits. Test Kits Compared
If you aren't going to use PoolMath (which is better than the Orenda calculator, report your K-2006 results as follows

FC
CC
pH
TA
CH
CYA
Water temperature
Salt (if using a SWG)

TFP also uses CSI, which is a better index for pools. LSI is an old school index used more for boilers.

ORP doesn't reliably correspond to FC levels in residential pools - especially outdoor residential pools. FC/CYA ratio is a much much better indicator of sanitation levels as opposed to ORP. Additionally, with CYA levels above around 30, ORP becomes even less reliable.
When is the last time the ORP probes were cleaned and inspected?
When is the last time you had ORP calibrated by a professional company the specializes in ORP calibration?

 

[KevinL]

What’s your test kit say the pH is? The graph you showed doesn’t say much and I’d suspect the pH drop is not real because it doesn’t act like that unless you got a lot of low pH rain or have been adding acid.

My test kit says the pH is 7.9. Simultaneously, my sensor says it's 8.1. Not horrible, but not that close. By the way, I used the method described here (testing pH when FC > 10) to measure pH.

 

[KevinL]

Use your K-2006 and PoolMath when discussing issues here.
Adding in your Smart Pool Monitor and Orenda calculator just confuses the issue - especially when you don't mention them or show them in your signature.

TFP is based on accurate test results from one of the recommended test kits. Test Kits Compared
If you aren't going to use PoolMath (which is better than the Orenda calculator, report your K-2006 results as follows

FC
CC
pH
TA
CH
CYA
Water temperature
Salt (if using a SWG)

TFP also uses CSI, which is a better index for pools. LSI is an old school index used more for boilers.

ORP doesn't reliably correspond to FC levels in residential pools - especially outdoor residential pools. FC/CYA ratio is a much much better indicator of sanitation levels as opposed to ORP. Additionally, with CYA levels above around 30, ORP becomes even less reliable.
When is the last time the ORP probes were cleaned and inspected?
When is the last time you had ORP calibrated by a professional company the specializes in ORP calibration?

Like I said, I don't rely on ORP much at all.

I cleaned and calibrated by sensor about 1.5 months ago. Also, I do use Taylor K-2006 kit.

I'd have to disagree on the Orenda calculator. I've found it accurate and convenient.

 

[KevinL]

What’s your test kit say the pH is? The graph you showed doesn’t say much and I’d suspect the pH drop is not real because it doesn’t act like that unless you got a lot of low pH rain or have been adding acid.

My test kit says the pH is 7.9. Simultaneously, my sensor says it's 8.1. By the way, I used the method described here (testing pH when FC > 10) to measure pH since my FC is around 12 ppm now.

 

[mgtfp]

I reckon there is something dodgy going on with the automated tester.

I once got weak and bought a Wifi Pool Kit from Atlas. Turned out to be absolutely useless, as soon as the sun hit the electronics box in the late morning, the pH signal appeared to crash. I later did some experiments by placing the sensor probe in a pH 4 buffer solution in a constant temperature environment and varied the temperature around the electronics box, and showed a direct correlation between shown pH value and the temperature of the electronics box. Returned it and got a refund.

Here is a post that showed the alleged pH over two days:

Well, that was quite disappointing. That Wifi Kit was pretty much useless. I bought it via an Australian distributor. Turned out they sent me an older model to start with. Could have lived with that, but something in the electronics is very temperature sensitive. Here a screenshot with pH signal of the probe in the pool pipes, 2 days overlaid in one graph:

View attachment 508535

Each day around noon, the hit hit for an hour or so the control box. In that time the pH signal crashed.

I then did a test where I placed the probe into pH 4 buffer solution which I kept at constant temperature. I then changed the room temperature where the Wifi Kit was placed in, and saw the same behaviour.

Atlas was useless in the process. I first got in touch with them about some general questions, which they were quite helpful with. As soon as I mentioned that something is not right, they stopped replying.

Aussie distributor was very good about it, got a refund in the end.

[Edit]
Just for completeness here the picture from above link, showing the alleged pH over two different days, overlaid as red and back into one graph:

[/Edit]

Not saying that all automated testers are necessarily as crappy as the one that I got (even other Atlas setups seem to be OKish), but when I see fluctuations like the ones you are showing then I am suspicious of the test setup and quite confident that fluctuations like that are chemically impossible.

 

[Bperry]

Like I said, I don't rely on ORP much at all.

I cleaned and calibrated by sensor about 1.5 months ago. Also, I do use Taylor K-2006 kit.

I'd have to disagree on the Orenda calculator. I've found it accurate and convenient.

Your problem seems to be originating from the ORP measurement system. Can you share test data over the same time period from your Taylor test kit? Or measure the pH every day over the next week using the test kit to find out if the variation is measurable with that as well.

 

[ajw22]

ORP sensor is used to manage chlorination.

pH uses a different sensor.

 

[KevinL]

I reckon there is something dodgy going on with the automated tester.

I once got weak and bought a Wifi Pool Kit from Atlas. Turned out to be absolutely useless, as soon as the sun hit the electronics box in the late morning, the pH signal appeared to crash. I later did some experiments by placing the sensor probe in a pH 4 buffer solution in a constant temperature environment and varied the temperature around the electronics box, and showed a direct correlation between shown pH value and the temperature of the electronics box. Returned it and got a refund.

Here is a post that showed the alleged pH over two days:



[Edit]
Just for completeness here the picture from above link, showing the alleged pH over two different days, overlaid as red and back into one graph:
View attachment 542050
[/Edit]

Not saying that all automated testers are necessarily as crappy as the one that I got (even other Atlas setups seem to be OKish), but when I see fluctuations like the ones you are showing then I am suspicious of the test setup and quite confident that fluctuations like that are chemically impossible.

Thanks, that very useful info.

 

[KevinL]

Your problem seems to be originating from the ORP measurement system. Can you share test data over the same time period from your Taylor test kit? Or measure the pH every day over the next week using the test kit to find out if the variation is measurable with that as well.

Sure, But the best I can do is show you a graph for ORP and another weekly graph for PH. I attached them.

 

[Bperry]

Sure, But the best I can do is show you a graph for ORP and another weekly graph for PH. I attached them.

Is the pH measured with the Taylor kit or some automation? If you’re trying to debug a measurement error, you kinda need two ways to measure the pH. The pH in your graph looks fine.

 

[KevinL]

Is the pH measured with the Taylor kit or some automation? If you’re trying to debug a measurement error, you kinda need two ways to measure the pH. The pH in your graph looks fine.

Both. The picture shows the ph measured by my automation. But I found out that it's not very accurate at least when it dips down like that. I'm not sure what's going on with it.

 

[proavia]

Test your pH every day at about the same time using the Taylor pH test.
Post your results for a week here.