Low ph out of RO
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You cannot accurately measure the pH of ro or RO/DI water, it is meaningless. There are too few ions to measure.
Consider RO/DI to be neutral pH and it quickly takes on the pH of whatever is added to it or it is added to.
If you effluent TDS is 3 you need new DI resin or need to add a DI if it is RO only.
Consider RO/DI to be neutral pH and it quickly takes on the pH of whatever is added to it or it is added to.
If you effluent TDS is 3 you need new DI resin or need to add a DI if it is RO only.
OP
OP
Nickh517
Community Member
Ok makes sense. What I can do besides add buffer to raise pH when first mixing water. I am using kent reef salt. I bought a box of instant ocean and am switching over to it. Do I need to do it slowly as the chemistry my be slightly different from kent. I might add once this is gone I plan to use red sea coral
http://spectrapure.com/RO-RODI/RODI...ers-Chlorine-Test-KitMeters-Chlorine-Test-Kit
They don't come any better at twice the price.
They don't come any better at twice the price.
Randy Holmes-Farley
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Do not add buffers to to your RO water, unless it is simply the way you dose alkalinity.
All buffers are alkalinity additives, and adding it without monitoring alk will boost the alk too high.
Buffers are also not a good way to raise pH, even if that is the goal.
The pH of RO/DI water is not EVER the cause of low pH in a reef tank, no matter what you observe it to be.
This has more:
pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/
and
Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2005-05/rhf/index.htm
from the last one:
Final Effluent pH
Aside from the issues discussed above concerning the effluent’s pH when the DI resin becomes depleted, the final pH coming out of an RO/DI system should not significantly concern reef aquarists. Many aquarists with low pH problems have asked, for example, if their aquarium’s low pH may be caused by their replacing evaporated water with RO/DI water that they measure to have a pH below 7. In short, the answer is no, this is not a cause of low pH nor is it something to be generally concerned about, for the following reasons:
1. The pH of totally pure water is around 7 (with the exact value depending on temperature). As carbon dioxide from the atmosphere enters the water, the pH drops into the 6’s and even into the 5’s, depending on the amount of CO2. At saturation with the level of CO2 in normal (outside) air, the pH would be about 5.66. Indoor air often has even more CO2, and the pH can drop a bit lower, into the 5’s. Consequently, the pH of highly purified water coming from an RO/DI unit is expected to be in the pH 5-7 range.
2. The pH of highly purified water is not accurately measured by test kits, or by pH meters. There are several different reasons for this, including the fact that highly purified water has very little buffering capacity, so its pH is easily changed. Even the acidity or basicity of a pH test kit’s indicator dye is enough to alter pure water’s measured pH. As for pH meters, the probes themselves do not function well in the very low ionic strength of pure freshwater, and trace impurities on them can swing the pH around quite a bit.
3. The pH of the combination of two solutions does not necessarily reflect the average (not even a weighted average) of their two pH values. The final pH of a mixture may actually not even be between the pH’s of the two solutions when combined. Consequently, adding pH 7 pure water to pH 8.2 seawater may not even result in a pH below 8.2, but rather might be higher than 8.2 (for complex reasons relating to the acidity of bicarbonate in seawater vs. freshwater).
All buffers are alkalinity additives, and adding it without monitoring alk will boost the alk too high.
Buffers are also not a good way to raise pH, even if that is the goal.
The pH of RO/DI water is not EVER the cause of low pH in a reef tank, no matter what you observe it to be.
This has more:
pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/
and
Reverse Osmosis/Deionization Systems to Purify Tap Water for Reef Aquaria by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2005-05/rhf/index.htm
from the last one:
Final Effluent pH
Aside from the issues discussed above concerning the effluent’s pH when the DI resin becomes depleted, the final pH coming out of an RO/DI system should not significantly concern reef aquarists. Many aquarists with low pH problems have asked, for example, if their aquarium’s low pH may be caused by their replacing evaporated water with RO/DI water that they measure to have a pH below 7. In short, the answer is no, this is not a cause of low pH nor is it something to be generally concerned about, for the following reasons:
1. The pH of totally pure water is around 7 (with the exact value depending on temperature). As carbon dioxide from the atmosphere enters the water, the pH drops into the 6’s and even into the 5’s, depending on the amount of CO2. At saturation with the level of CO2 in normal (outside) air, the pH would be about 5.66. Indoor air often has even more CO2, and the pH can drop a bit lower, into the 5’s. Consequently, the pH of highly purified water coming from an RO/DI unit is expected to be in the pH 5-7 range.
2. The pH of highly purified water is not accurately measured by test kits, or by pH meters. There are several different reasons for this, including the fact that highly purified water has very little buffering capacity, so its pH is easily changed. Even the acidity or basicity of a pH test kit’s indicator dye is enough to alter pure water’s measured pH. As for pH meters, the probes themselves do not function well in the very low ionic strength of pure freshwater, and trace impurities on them can swing the pH around quite a bit.
3. The pH of the combination of two solutions does not necessarily reflect the average (not even a weighted average) of their two pH values. The final pH of a mixture may actually not even be between the pH’s of the two solutions when combined. Consequently, adding pH 7 pure water to pH 8.2 seawater may not even result in a pH below 8.2, but rather might be higher than 8.2 (for complex reasons relating to the acidity of bicarbonate in seawater vs. freshwater).
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TheEngineer
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You got the expert @Randy Holmes-Farley now. I'll step aside 
I was just going to add that when you have very pure water, like from an RO membrane, it has low pH buffering ability so smaller amounts of hydrogen ions are required to lower the pH.
I was just going to add that when you have very pure water, like from an RO membrane, it has low pH buffering ability so smaller amounts of hydrogen ions are required to lower the pH.
120reefkeeper
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+1 spectrapure
I would have purchased the Spectrapure unit I recommended earlier. Sounds like you probably have low TDS to begin with so you probably don't need dual DI. You also don't need the inline TDS meter since they lack the accuracy of a good handheld.
http://spectrapure.com/RO-RODI/RODI...ement-Filter Kit-TDS Meters-Chlorine-Test-Kit
http://spectrapure.com/RO-RODI/RODI...ement-Filter Kit-TDS Meters-Chlorine-Test-Kit
