when to read pH

[engrav]

Been a while but with
same pool
same equipment
same chlorine method
not lots to discuss but now

Have Apera pH meter. Is cool, more fun than color matching with 82 year old eyeballs but...
Water is cold, like 45.
When I first put the meter in I might see 7.3. After sloshing around for a minute or two I might see 7.9.

Which is the "real" pH? Which should I use?

 

[wireform]

Water should be brought up to room temperature first

 

[engrav]

thanks, can do
while waiting saw this, see screenshot, suggests changes too small to worry about
but my change from 7.3 to 7.9 is much larger

 

[Bperry]

Been a while but with
same pool
same equipment
same chlorine method
not lots to discuss but now

Have Apera pH meter. Is cool, more fun than color matching with 82 year old eyeballs but...
Water is cold, like 45.
When I first put the meter in I might see 7.3. After sloshing around for a minute or two I might see 7.9.

Which is the "real" pH? Which should I use?

My inexpensive pH meter instructions said to keep the probe in the water until the reading stabilized. Mine tended to rise the longer I kept it in there. I don’t use the meter anymore because of that.

 

[JoyfulNoise]

First off, make sure you have fully calibrated the probe. A 3-point calibration (4.01, 7, 10.01) is the most accurate.

Second, make sure you turn on the probe ONLY AFTER it is removed from the KCl storage solution and rinsed off under tap water.

Turn the probe on and let the electronics stabilize for a 30 sec or so BEFORE testing anything.

Put the probe into the pool water (easiest to just scoop up a big sample using a 2-cup measuring cup rather than standing outside in the cold) and GENTLY move it around. Wait for the SMILEY FACE icon to appear. When it does, that is your reading.

 

[JamesW]

 

[JamesW]

The reading should be accurate if you follow the calibration and testing instructions.

You should not be getting a different reading at different temperatures.

PH60 Premium Digital Pocket Waterproof pH Meter pH Pen Tester Kit with Replaceable Probe and Backlight-Apera Instruments

The Apera Instruments PH60 Premium Digital Pocket pH Meter / pH Pen Tester is ideal for all kinds of regular aqueous solution's testing, such as hydroponics, aquaculture, pools& spas, water treatment, cooling towers, etc. Can be replaced with ORP probe.

aperainst.com

https://s3.amazonaws.com/zcom-media/sites/a0i0L00000VJHGsQAP/media/mediamanager/PH60_Tester_Manual_v8.3.pdf

 

[JamesW]

The pH might rise due to carbon dioxide offgassing, which happens as a result of warming and/or shaking like what happens to a soda or beer going flat as it sits out in a glass.

I would not think that the pH would rise a lot unless the TA was really high and you did a lot of agitation and the sample got really warn, but I do not know exactly how much pH rise from CO₂ offgassing is to be expected.

If you see a bunch of tiny bubbles developing, that might be CO₂.

Try the pH drop test and a sample at the first cold temperature and a sample at the warmer temperature.

 

[JamesW]

You also have to be careful that there are no bubbles on the probe.

Bubbles will make the test inaccurate.

 

[engrav]

thanks all, nice video
today I did pH with the old calorimetric method and read 7.8
then used the device, same thing, first funny face at about 7.3, but kept stirring and pH went up to 7.9, then stopped changing with another funny face
can only conclude to match the calorimetric method gotta keep stirring till it stops changing
is Ok, I can do that

 

[JamesW]

Water should be brought up to room temperature first

There is no reason that the water temperature needs to be "Room Temperature".

Taylor gives the recommended range for temperature as 50℉ to 90℉.

Apera gives the recommended range for temperature as 41℉ to 113℉.

Do pool or spa water samples have to be at "room temperature" before testing begins?

For consistency, reliability, and accuracy, we recommend sample temperatures to be between 50-90℉.

Sample temperatures <50℉ or >90℉ may produce unexpected color development.

https://www.taylortechnologies.com/en/page/105/questions-in-our-poolspa-mailbag

https://s3.amazonaws.com/zcom-media/sites/a0i0L00000VJHGsQAP/media/mediamanager/PH60_Tester_Manual_v8.3.pdf

PH60 Premium Digital Pocket Waterproof pH Meter pH Pen Tester Kit with Replaceable Probe and Backlight-Apera Instruments

The Apera Instruments PH60 Premium Digital Pocket pH Meter / pH Pen Tester is ideal for all kinds of regular aqueous solution's testing, such as hydroponics, aquaculture, pools& spas, water treatment, cooling towers, etc. Can be replaced with ORP probe.

aperainst.com

 

[JamesW]

can only conclude to match the calorimetric method gotta keep stirring till it stops changing
is Ok, I can do that

See what Apera has to say.

The meter should be accurate at 41℉ degrees or higher.

If your readings are off, the device might be defective or you might have some type of other issue.

Contact Us - Apera Instruments

Apera Instruments- Contact us.

aperainst.com

[email protected]

Submit a ticket

support.aperainst.com

 

[JoyfulNoise]

We have seen at least one thread where a member had to return their meter for a new one as the probe tip was defective. Others have experienced issues with the probe drying out.

If the probe arrived without its storage cap on or there was minimal moisture in the cap when it arrived, you should soak the probe tip in 3M KCl storage solution for at least 24 hours. Probes should always be stored in the KCl solution, never in tap water or distilled water. You should also then perform a 3-point calibration with 4.00, 7.00, & 10.01 calibrating standards. This will ensure the most accurate a repeatable results.

 

[JamesW]

Apera also suggests that the calibration be done at the same temperature as the sample.

Maybe the temperature reading is off causing some discrepancies.

Verify that the temperature reading is accurate.

 

[engrav]

again, if I keep stirring for a half minute or a minute the temp rises, then stops, from about 7.3 to about 7.9; and the 7.9 is dead on with the old calorimetric method
so I think the final is accurate

we are talking 40degree water with jar and probe at room temp; maybe the glass, water, probe all need to achieve temperature equilibrium before it displays the final value

maybe if the probe is 60degrees and the water is 40degrees the probe gets mixed up

 

[JamesW]

If the water temperature reading is accurate, then the pH reading should be accurate.

The temperature reading works pretty fast.

It might take a couple of seconds to stabilize, but I would think that the tester would wait until the temperature sensor reading stopped moving before it takes a pH reading.

 

[JamesW]

The temp reading should stop moving in about 5 seconds or less.

In any case, contact Apera and see what they say.

 

[engrav]

So called 'em. Said if temp water and temp probe grossly different strange things happen. So if water 40 and probe 68, put probe in water and let sit for couple three minutes. So I did that and voila.
Colorimetric was 7.6 with old eyeballs and pH meter was 7.61.
So issue solved. Gotta let 'em sit for a bit.
Now on to solve Israeli Palestinian issue.
Thanks.

 

[Sarah and Nate]

Thanks so much for the followup @engrav !

 

[DanF]

Yes thanks for the followup also. I've witnessed similar behavior with my Apera pH60...i really need to let it sit in the sample water a while if there's a temperature difference between sample water and device.

Edited to add: The video in post #6 describes how to calibrate to 3 different pH levels: 4, 7, 10. I called Apera about a year ago and was told that, if I was just using the PH60 for pool water testing, I only needed to calibrate to 7.

Let us know when you've solved the Israeli/Palestinian issue .