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Q & A: DI conductivity

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Most recent answer: 05/16/2013
Q:
Our plant DI water resistivity reads at around 17 Mohms-cm at the point of use sampling point but once it been supply to the process tank, it resistivity of the DI water in the process tank reads at around 5-6 Mohms-cm.Is there any suggestion or advise to help to improve the resistivity on the process tank. Thanks..
- Heng (age 37)
Singapore
A:
Heng-  What sort of system is used to transport the water to the process  tank?
Obviously, some pipes can leak ions into the water. Also, if at any point the water is exposed to air, it will pick up some dissolved CO2. That then partially dissociates leaving some ions, of which the most conductive is the H+ ion.
Have you measured the pH of the water at the sampling point and the process tank? If it's getting a little more acidic, you can check standard tables of conductivity vs. ionic concentrations to see if those H+ ions are mainly responsible for the conductivity increase. If not, then some sort of salt is leaching from the pipes.

Mike W.

(published on 05/16/2013)

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