Amazing pH discovery!

[Duffer]

The reason this post is going to the Equipment forum and not the Chemistry forum will become apparent shortly
:yo:

A few of you may have been following my pH 'nightmares' over on PSAS. It was driving me insane. No matter what I did and with near perfect water parameters, my pH just kept falling as read from my Reefkeeper probe/system. Recalibrated? yup! Fresh air pumped/bubbled in? yup! So I quit 'chasing' it. and it fell and fell, finally sitting around an impossible 6.8ish. I figured the probe died

Today I decided to yet again recal the probe. Everything went fine but nothing improved.

So..... what can make the pH probe read a 7.0 buffer correctly, a 10.0 buffer also correctly, but the sump reads impossibly?

Then the little lightbulb turned on. I scooped a cupful of tank water, dropped the probe in, and VIOLA! 7.9ish!!! Replace the probe into the sump and it falls all the way to 6.7-6.8

Problem defined? (I hope anyway) I have ordered A GROUNDING PROBE NOW!!!!!

 

[kpiotrowski]

I breifly scanned your 180 thread on psas. I'm not fully understanding the above "So..... what can make the pH probe read a 7.0 buffer correctly, a 10.0 buffer also correctly, but the sump reads impossibly".

my question is are you dosing straigh sodium bicarb ( baking soda)? if so are you baking it off first? if you don't bake off the Co2 it could contribute to low ph. just a thought!

I agree 6.8 ph is concering but I have never been one to chase ph...as you probably know your alk helps keep ph stable and stable is better than high.

 

[Duffer]

My realization (having worked with scientific equipment all my career) was that: even tho the probe is properly calibrated, and even tho it then reads the buffers correctly when retested, that once placed into the sump the reading seems awfully low.

Followed by: why would the same probe read super low in the sump but read much more reasonably when placed in the exact same water except in a cup instead of straight in the sump.

The sump/system itself is affecting the probe. Has to be electrical, doesn't it? (lack of grounding?)

 

[trido]

I think you're on the right track. The probe only uses a tiny amount of electricity. Probably 12VDC at 500 Milliamps or less amps. If you place the probe cord next to a wiring harness for a large return pump even the EMF can slightly effect your readings.

 

[kpiotrowski]

interesting. have you tried different postions in the sump or even put the probe in the DT? trying to follow here for future reference. I know I have heard you are not supposed to put probes too close together but that make you wonder why probe holders are so close too.

 

[oldsaint]

I would try unplugging electrical equipment and see if one has an effect.

 

[Duffer]

I would try unplugging electrical equipment and see if one has an effect.

This will be my next step, now that I know what I'm looking for :nerd:

 

[Maxx]

Subscribed for additional updates.....

 

[garydan]

Just a thought. This is from the SL2 module site on digitalaquatics.com:

"The pH port on the SL2 is an isolated pH port. This all but eliminates the affect ground loops and system interference when using multiple pH probes. Any standard pH probe with a BNC interface should work with the SL2."

This is listed as a feature of the SL2 because the SL1 is NOT an isolated pH port...

I'm guessing you're using the SL1 module (I am also). I've heard of people having issues with more than one pH probe using an SL1 module because it is not isolated. Sounds like you're seeing the "system interference" problem with it not being isolated.

 

[SkimHeavy]

Subscribed! Let's here what's new

 

[reefman069]

maybe you need a new ph probe

 

[Duffer]

maybe you need a new ph probe

Also entirely possible.
Ended up working this weekend so sorry for the slow updates but I did get a chance to climb under and unplug a few things.

I'll have to check which port the pH is wired into, but I only have that probe. That and the temp probe

UV sterilizer (I'd have bet money on this one) ..... no change
TLF Phosban .... no change
OBD pellet reactor ...... no change
Sump pump ..... no change
Sump light .... no change
heater ..... no change

Closed loop pump (which is outside in my water shed and pumps thru the crawl space) .... interesting effect! The pH immediately started climbing but then fell back down to about where it started. Once plugged back in the pH fell even further and then rose back to it's most recent steady 6.8-ish

I didn't have time to do any more research, like unplugging the LEDs or the Luft pump. The grounding cord is on its way. We'll see if it helps

 

[Duffer]

......aaaannd the grounding cord made ZERO difference!

So I went thru and unplugged the same stuff again but this time it also had no effect. Checked the probe connection. No effect. Moved the probe to a different place in the sump (as far as it would reach) no effect.

Still have to unplug my lights. Could just be a dying probe after all?