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Salinity Salt

Carbonic acid is partly why the pH is so low. The other reason is that RODI is very pure and most pH meters and tests don't work well for very pure water. Carbonic acid will dissipate with time. I no longer use RODI less than 48 hours unless I really need it. As Jim says, adding a powerhead will reduce the carbonic acid. Don't use an airpump though (I forget the reason cited).
 
bondolo said:
Carbonic acid is partly why the pH is so low. The other reason is that RODI is very pure and most pH meters and tests don't work well for very pure water. Carbonic acid will dissipate with time. I no longer use RODI less than 48 hours unless I really need it. As Jim says, adding a powerhead will reduce the carbonic acid. Don't use an airpump though (I forget the reason cited).
Click to expand...


Spectrapure's page shows the use of an air pump, and that is what I have always been told to use as well.

http://www.spectrapure.com/faq_p0.htm#calcc02

CO2_DIAGRAM.gif

http://www.spectrapure.com/CO2_SYSTEM.pdf
 
carbonic acid is basically protonated CO2. RO/DI water has nothing to buffer it, so it's pH is easily effected by acid. Salt water has a lot (relatively speaking) of buffer capacity, so disolved CO2 has a much smaller effect on pH. Acidified (from CO2), non- buffered water, while low in pH, will rapidly go to high pH when mixed with salt water (which is buffered for high pH).
 
I'll certainly trust that more than a random source I don't fully remember and can't reference. Ignore my previous advice about not using an air stone. :)

bondolo wanders off to look for an air line splitter to add an air line to his RO/DI reservoir
 
I don't really remember very much of my chemistry well, let alone all of my physics, so I'll just believe you guys, haha.

Over time I'm sure I'll pick it up again.
 
This hobby is great at resurrecting knowledge you learned in High School... chemistry, algae, geometry, biology, etc etc :) Heck, it even helped with my spanish since I was dealing with a collection station in Baja :lol:
 
BAYMAC said:
bondolo said:
Carbonic acid is partly why the pH is so low. The other reason is that RODI is very pure and most pH meters and tests don't work well for very pure water. Carbonic acid will dissipate with time. I no longer use RODI less than 48 hours unless I really need it. As Jim says, adding a powerhead will reduce the carbonic acid. Don't use an airpump though (I forget the reason cited).
Click to expand...


Spectrapure's page shows the use of an air pump, and that is what I have always been told to use as well.

http://www.spectrapure.com/faq_p0.htm#calcc02

CO2_DIAGRAM.gif

http://www.spectrapure.com/CO2_SYSTEM.pdf
Click to expand...

Nice links. Took me awhile to figure out what the second one was trying to accomplish. I think I understand it now! :)

--Trying real hard to remember all that college chemistry--
Is this really necessary? Seems like there would be so little CO2 or carbonic acid as not to matter. The first link states this is to extend the life of DI resins when the source water has low pH. Do you EBMUD folks have low pH water? Up here in cow and chicken country we get a pH of 8.0+ out of the tap.

As soon as salt is added, wouldn't the pH swing to a more stable range? I always consider RO/DI water to be 'unstable'. Even Discus keepers add minerals to their RO/DI to tame it's unstable nature.
 
RO + GAC lowers pH ;) For longer life of DI, you want to increase it. What I posted would need to be fed via a pump into your DI, then another holding tank.

RO water is used for top off as well, which is the tangent we took off on :) Kalk water topping off in specific.
 
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