Calcium Reactor pH probe calibration

[snarkes]

Okay, so maybe someone can help me here.

I calibrated my pH probe using 7 and 10 a few weeks ago. The probe is/was brand spankin new.

Two weeks ago I setup my calcium reactor (MRC CR2). I set it up in various ways with lower and higher bubble counts and effluent rates, but cannot get the pH inside the first chamber below 6.6 (was hoping to set it to keep the internal pH between 6.5 and 6.6).

Currently, it is setup with a 90 BPM and an effluent rate of 40mls per minute and it is reading a pH of 6.7. The bigger problem here is that the solenoid never shuts off... and by that I mean CO2 is constantly running.

I've been testing the tank daily to watch for spikes in alk. As of today the calcium is ~375 and alk is 3.5 meqs. The effluent tests with a calcium level of ~950.

Well... no one I've talked to seems to know whats going on... until I talked to a local guy today that said it was because I calibrated my pH probe with 7 and 10 instead of 4 and 7. I dont remember seeing an option for the 4 solution. Any truth to this possibility? If so... how do you calibrate it with the 4? And if not... what am I doing wrong?

 

[phuzzykins]

Yes, you should have calibrated with 4 and 7... when it displays "low cal" or something like that, you use the arrows to select the lower of the pH solutions you're using in calibration.

Having said that, 6.7 isn't too far below 7, and this isn't likely to be caused by using the wrong calibration solutions.

Check with MRC to see how much CO2 you should need to maintain a pH of 6.7 with 40ml/minute effluent. Also, you should measure the effluent alkalinity and give them that info.

My reactor takes roughly the same ratio of co2 to effluent to maintain pH between 6.4 and 6.6, but it's a different design.

 

[snarkes]

Thanks phuzzykins

I picked up some pH calibration solution so I'll try that. They were out of 7... so I picked up 4 and 10 (can always use 10 for calibrating the dt probe anyways). Can I use the 4 and 10 to run the calibration? Or do I really need the 7?

As for setting up the reactor. I followed the directions from the MRC site, but I'll go back and do it again from scratch.

 

[GlenG]

You will need 7 for all calibrations. High range and low range. 7 is the high point for the low range cal and the low point for the high range cal.