My RO pH seems off...

[h22lude]

I know water pH doesn't mean much by itself for mash pH but something just seems off.

I bought my RO system from Buckeye Hydro. It is hooked up to the cold side of my brew sink. I also have an inline TDS meter.

My TDS in is 88ppm and out is 6ppm.

My starting water from May 2016 is

pH 9.6
TDS 109ppm

Na 19
Ca 13
Hardness CaCO3 37
SO4-S 6
Cl 28
HCO3 19
Alkalinity CaCO3 22

I used a MW-102. Calibrated with 4.0 and 7.0 solution from Brew Masters which I bought from More Beer. Checked my RO water and it was 9.71. Put probe back in solutions and they were 3.99 and 6.99. Put probe back in a new glass of RO and it was 9.74.

Why is it so high? And is that a problem?

 

[jdauria]

Wow, that seems high. pH systems would normally lower the pH not increase it. Do you have a calcite filter on the system? Those are usually used to increase pH and to make RO water taste more like spring water.

 

[ajdelange]

That does seem a little strange but note that alkalinity of 22 and pH of 9.6 implies bicarbonate content of 16.5 mg/L and carbonate content of 2.1 mg/L while pH of 9.71 could also be attained with bicarbonate of 2.9 mg/L and carbonate at 0.46 mg/L. These represent rejections of about 85% for those two ions and your TDS numbers suggest rejection of about 93%. Thus I surmise that your high pH is caused by bicarbonate and carbonate which made it through the membrane.

If this water is allowed to stand exposed to air eventually the bicarbonate and carbonate should be neutralized and the pH should rise.

 

[bucketnative]

@ajdelange - What about his statement that he is measuring the pH of the RO in a glass container. In our lab, we typically measure the pH of non-buffered water in plastic containers because the glass (especially Type 1 borosilicate glass) will tend to result in more alkaline measurements. Could there also be any residues from detergents on the glass?

 

[h22lude]

Wow, that seems high. pH systems would normally lower the pH not increase it. Do you have a calcite filter on the system? Those are usually used to increase pH and to make RO water taste more like spring water.

No this system has a 1 micron sediment, .5 micron carbon block and RO membrane. I don't know much about water but I thought it was odd the RO water pH was this high and didn't decrease. The Ward Labs report was from May 2016. My tap water pH could be higher now. I can test it later.

That does seem a little strange but note that alkalinity of 22 and pH of 9.6 implies bicarbonate content of 16.5 mg/L and carbonate content of 2.1 mg/L while pH of 9.71 could also be attained with bicarbonate of 2.9 mg/L and carbonate at 0.46 mg/L. These represent rejections of about 85% for those two ions and your TDS numbers suggest rejection of about 93%. Thus I surmise that your high pH is caused by bicarbonate and carbonate which made it through the membrane.

If this water is allowed to stand exposed to air eventually the bicarbonate and carbonate should be neutralized and the pH should rise.

This system is a little over a year old. I haven't replaced any of the two filters or RO membrane but I also haven't used it a ton. Maybe the filters need to be replaced.

Is it bad that the RO pH is that high? Could that cause any issues? I know water pH itself doesn't tell us much in regards to mash pH but didn't know if that high of a pH especially from an RO system could cause any off flavors or mashing issues.

@ajdelange - What about his statement that he is measuring the pH of the RO in a glass container. In our lab, we typically measure the pH of non-buffered water in plastic containers because the glass (especially Type 1 borosilicate glass) will tend to result in more alkaline measurements. Could there also be any residues from detergents on the glass?

I always use glass containers for measuring. Never knew that could cause issues. Not sure what type of glass it is. I was actually thinking last night about using small disposable bathroom cups instead of what I was using just because it would use less solution (https://www.amazon.com/dp/B002T5DP0G/?tag=skimlinks_replacement-20). Would these be better?

 

[ajdelange]

@ajdelange - What about his statement that he is measuring the pH of the RO in a glass container.

I would think the amount of alkali leached from the glass in the length of time it takes to do a pH measurement would be totally swamped by the 2 or so ppm bicarbonate from the source water which made it through the RO membrane.

 

[ajdelange]

I know water pH itself doesn't tell us much in regards to mash pH...

Is it bad that the RO pH is that high?

I think you have answered your own question.

Could that cause any issues? ...but didn't know if that high of a pH especially from an RO system could cause any off flavors or mashing issues.

If it doesn't cause problems at alkalinity of 22 ppm it isn't going to cause problems at alkalinity of 2.

 

[h22lude]

I think you have answered your own question.

I figured as much. I wasn't sure if that high of a pH from RO water meant other problems were occurring.

I need to replace the filters, which I will do soon. I may send it off to Ward Labs just to see what comes back.

 

[IslandLizard]

I figured as much. I wasn't sure if that high of a pH from RO water meant other problems were occurring.

I need to replace the filters, which I will do soon. I may send it off to Ward Labs just to see what comes back.

Some aquarium or pool test kits include an alkalinity test, you use drops until it turns from green to pink, IIRC. The number of drops x a factor, is your alkalinity.

Not sure if that could be useful for ad hoc tests.

I'm wishing for the time to come a brewing water test can be done at home for less than $1 for all the variables we're most interested in, and without having to spend $200-300 up front...

 

[Buckeye_Hydro]

I figured as much. I wasn't sure if that high of a pH from RO water meant other problems were occurring.

I need to replace the filters, which I will do soon. I may send it off to Ward Labs just to see what comes back.

Remember that the prefilters (sediment and carbon) should be replaced much more often than the RO membrane. You can find a one page write-up about when to change your filters on our FAQ page. It's the very first FAQ, here.

Russ