Problems with my Bluelab PH pen

[IsanFarmer]

I invested in a Bluelab PH pen but after a few months of using it I'm starting to think that it isn't working properly. I have cared for this pen meticulously, making sure it is hydrated every week in KCI solution, cleaned and calibrated once a month, and rinsed after every use. The probe hasn't been struck or dropped since I've had it either. Today I discovered that the reason why I can never get a stable reading with the pen is because I am using RO water and this prevents a stable reading because according to their website:

"As reverse osmosis removes all ionic and solid components present there should only be water present. The water molecules are made up of equal ratios of Hydrogen (H+) and Hydroxide (OH-) ions and so the pH should be neutral (7). However, as these ions are bound up in a water molecule (H2O) they cannot interact with the pH probe so you will not obtain a reading. High sensitivity probes can be used, but are a lot more expensive as they use a different technology, but these are not necessary for agricultural measurements."

According to their website the solution to this problem is this:

"It is popular to add a small amount of Calcium Magnesium (calmag) to RO water to be able to obtain a pH reading as our probes can measure pH once there are some ions present (Cl- and Mg2+). However, the addition of calmag doesn’t change the pH of the solution at all as it doesn’t contain Hydrogen or hydroxide ions which are the only ions that can change the pH. Even though you may now receive a reading, it has not changed from before you added the calmag, so what’s the point?"

However, I have added CalMag to the water I am testing and it has made no difference. The reading still fluctuates and drops by .1 every 30 seconds or so until the pen eventually switches itself off. Has anybody else experienced this problem with a Bluelab pen? And is it normal for the pen to switch itself off after about 5 minutes whenever I use it? If the reading still keeps fluctuating until the pen switches itself off there is no way of knowing what the real reading is.

The obvious solution to this problem would be to stop using RO water, but I live in Thailand and the tap water is not safe to drink. I know about various methods that can be used to dechlorinate tap water etc but how do I know what is in the water to begin with, and what is it I need to take out of the water to make it suitable for use?

 

[ArtfulCodger]

I have the same pen and it behaves similarly. I guess I don't quite understand the problem. You bought an RO machine to get rid of the TDS in your tap water. It does its job so well that the pen can't measure it. That's good, right?

 

[IsanFarmer]

I have the same pen and it behaves similarly. I guess I don't quite understand the problem. You bought an RO machine to get rid of the TDS in your tap water. It does its job so well that the pen can't measure it. That's good, right?

I use RO water from machines in the street. They're everywhere in Thailand. I use RO water to save me the trouble of taking chlorine out of tap water. If the reading on my pen keeps dropping until it switches itself off, how can you be sure what the reading is? Isn't the reading supposed to stop at some point so you know that's what the reading is? If the reading keeps dropping until the pen switches off, how can you be sure it wouldn't have continued to do that if the pen hadn't switched off? The reading on my pen drops by .1 approximately every 30 seconds until the pen switches off after 4 minutes. Is it a safe enough assumption that if the pen switches itself off after 6 minutes the reading would have dropped another .4 by then? If the pen can't give me an accurate reading for the PH, how is that good?

 

[ArtfulCodger]

I use RO water from machines in the street. They're everywhere in Thailand. I use RO water to save me the trouble of taking chlorine out of tap water. If the reading on my pen keeps dropping until it switches itself off, how can you be sure what the reading is? Isn't the reading supposed to stop at some point so you know that's what the reading is? If the reading keeps dropping until the pen switches off, how can you be sure it wouldn't have continued to do that if the pen hadn't switched off? The reading on my pen drops by .1 approximately every 30 seconds until the pen switches off after 4 minutes. Is it a safe enough assumption that if the pen switches itself off after 6 minutes the reading would have dropped another .4 by then? If the pen can't give me an accurate reading for the PH, how is that good?

I understand your point. I was conflating TDS and pH. Sorry for the confusion. If you mix up a batch of nutes, do you get a good pH reading? I'd be tempted to check the pH of the RO water with cheap test strips.

 

[IsanFarmer]

I understand your point. I was conflating TDS and pH. Sorry for the confusion. If you mix up a batch of nutes, do you get a good pH reading? I'd be tempted to check the pH of the RO water with cheap test strips.

Yes I wondered why you mentioned TDS and no, when I was mixing up some nutes the other day the pen was doing the same thing. I think it's fucked. I bet I've got you thinking now if your pen behaves the same way? If it does, at what point do you satisfy yourself that the reading you get is correct? Do you use RO water as well?

I've done a lot of research today into RO water and cannabis cultivation and I've reached the conclusion I should stop using it immediately. I think it's fucked my PH pen and I need to replace it, which is a bastard because it's an expensive one and I've barely used it.

 

[ArtfulCodger]

Yes I wondered why you mentioned TDS and no, when I was mixing up some nutes the other day the pen was doing the same thing. I think it's fucked. I bet I've got you thinking now if your pen behaves the same way? If it does, at what point do you satisfy yourself that the reading you get is correct? Do you use RO water as well?

I've done a lot of research today into RO water and cannabis cultivation and I've reached the conclusion I should stop using it immediately. I think it's fucked my PH pen and I need to replace it, which is a bastard because it's an expensive one and I've barely used it.

Yeah, I get good stable pH readings once I've mixed up a batch. Again, I was thinking TDS when you were talking about pH. My bad. The Blue Lab website says RO water can cause permanent damage if you use it to hydrate the probe. Maybe that's what you're dealing with. https://support.bluelab.com/hydrate-bluelab-ph-pen

 

[IsanFarmer]

Yeah, I get good stable pH readings once I've mixed up a batch. Again, I was thinking TDS when you were talking about pH. My bad. The Blue Lab website says RO water can cause permanent damage if you use it to hydrate the probe. Maybe that's what you're dealing with. https://support.bluelab.com/hydrate-bluelab-ph-pen

I've never used RO water to hydrate the pen, I've only ever used KCI solution, but they say on the Bluelab website you should NEVER soak your pen in RO water. If the manufacturers are so opposed to soaking in RO water and make it sound so harmful, then it follows that it's probably quite harmful in small doses too? For example, when you're testing the PH of RO water? I hope some other people who have had a similar experience reply to this thread because I'm starting to think I've fucked this pen by using RO water for my plants.

 

[Zill]

RO - molten hydrogen oxide. That is all.

To read pH in RO water add a small quantity of table salt, pinch. Anything that ionizes in water. That will stabilize the probe.

 

[IsanFarmer]

RO - molten hydrogen oxide. That is all.

To read pH in RO water add a small quantity of table salt, pinch. Anything that ionizes in water. That will stabilize the probe.

Yes I heard you can do the same with CalMag which I tried but that didn't work either, the reading was still drifting.

 

[Zill]

Isan,

In pharmaceuticals we made our own water, WFI, Water for injection. About $15/liter. Take RO water and pass it over 5 or 6 multi effect still. That’s WFI. pH daily testing of the WFI was done after it had some salt added.

Zill.

 

[IsanFarmer]

Take RO water and pass it over 5 or 6 multi effect still.

Zill.

Could you elaborate on this part of the process?

 

[Zill]

Sure..

In a typical stand alone self supported biologics Manufacturing facility potable water is hard piped to the facility. Some of that portable water is diverted to the RO membranes. The resulting RO water can be used for certain operations like clean in place and vessel rinsing. Most of the RO is sent to the WFI stills. RO is turned to steam and that steam is condensed. That first condensate from the first effect still is sent to the next downstream still. The condensate is turned to steam and condensed again in the second effect downstream still. This goes on typically for 5 or 6 effect stills.

WFI is used whenever there is product contact. Fermentation, downstream processing and certainly for any final product formulation. Buffer make up and holding vessels are not cleaned in place but only rinsed with RO water.

Stills are used but are slowly being replaced by water vapor compression.