PH Probe Wierdness

will16 · 08/17/2008, 09:23 AM

I have a pinpoint ph probe in my sump for the past 4 months. When I set it up, I calibrated it with ph 7 and ph 10 calibration fluids. I had checked it against the api chemical test and a friends portable ph probe and everything checked out.

Recently I noticed that my ph started creeping up. Normally I am in the 8.1 - 8.3 range now I was in the 8.2-8.4 range. I had around the same time switched to the bulkreefsupply 2 part solutiion from b-ioninc. I assumed the increase was because of that. It continued to rise, almost to 8.5 so I cleaned the probe and recalibrated in ph 7 and 10 solution again. Before the recalibration, the ph read 8.37. After calibration, it read 8.04. That was a big change so I calibrated again to be sure and after the second calibration, the ph now read 8.17???

The next day, I took it out again and cleand and recalibrated a third time. This time I really let it sit in the calibration solutions for a while to make sure the values were steady. After the calibration, I put the probe in the 2 calibration fluids and got readings of 6.98 and 10.01. That's pretty close. When I put back into the sump, I got a reading of 8.0 (it was 8.17 right before this calibration). The api chemical test shows 8.4 and my friends portable ph probe read 8.7!

Which one should I believe? Should my probe be right since it correctly read the ph 7 and 10 solutions? Don't know when the portable ph probe was calibrated so that may not be so reliable but the api ph test was solid at 8.4 over a multiple tests.

Confused. Is it time for a new probe?

Thanks.

08/17/2008, 09:23 AM	#1
will16 Registered Member Join Date: Jan 2008 Location: Northern NJ Posts: 1,812	PH Probe Wierdness I have a pinpoint ph probe in my sump for the past 4 months. When I set it up, I calibrated it with ph 7 and ph 10 calibration fluids. I had checked it against the api chemical test and a friends portable ph probe and everything checked out. Recently I noticed that my ph started creeping up. Normally I am in the 8.1 - 8.3 range now I was in the 8.2-8.4 range. I had around the same time switched to the bulkreefsupply 2 part solutiion from b-ioninc. I assumed the increase was because of that. It continued to rise, almost to 8.5 so I cleaned the probe and recalibrated in ph 7 and 10 solution again. Before the recalibration, the ph read 8.37. After calibration, it read 8.04. That was a big change so I calibrated again to be sure and after the second calibration, the ph now read 8.17??? The next day, I took it out again and cleand and recalibrated a third time. This time I really let it sit in the calibration solutions for a while to make sure the values were steady. After the calibration, I put the probe in the 2 calibration fluids and got readings of 6.98 and 10.01. That's pretty close. When I put back into the sump, I got a reading of 8.0 (it was 8.17 right before this calibration). The api chemical test shows 8.4 and my friends portable ph probe read 8.7! Which one should I believe? Should my probe be right since it correctly read the ph 7 and 10 solutions? Don't know when the portable ph probe was calibrated so that may not be so reliable but the api ph test was solid at 8.4 over a multiple tests. Confused. Is it time for a new probe? Thanks.