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pH of my DM water is too high

sir, pH of my DM water is around 8.5, so suggest how to bring it to normal 7 pH as I am new

Bhadresh Desai
working for chemical industry - surat India
October 28, 2010

dear sir, you should balance raw water flow of your d.m. water input in d.m. plant or recharge it.

Agrawal Abhishek
- Khirkiya M.P. India
November 14, 2010

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Higher pH of DM Water may be due to dissolved CO2.Try boiling and cooling the water sample and check the pH again.

Subramanian Ramajayam
consultant - Bangalore, India
January 7, 2011

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High pH in a separate bed DM system is not uncommon. It is common when the anion resin has recently been regenerated. It also occurs for a short rinse up time when the flow has been stopped for some time, and then is re-started.

A third cause of high pH is fouling of the anion resin, usually by hardness. This is always accompanied by long rinse times and high pH, high conductivity water during the initial part of the anion resin cycle.

If the pH is persistently high throughout the anion resin cycle, then the problem is probably sodium leakage from the cation exchanger. Any sodium leakage from the cation exchanger becomes sodium hydroxide in the anion exchanger, which elevates both the pH and the conductivity. 1 mg/L of sodium hydroxide (which is only a fraction of a mg/L of sodium) is approximately 4.9 microSiemens of conductivity.
The correction for this is to improve the cation resin regeneration and rinsing. How to do this depends upon whether your system is a co-current or countercurrent regenerated system.

Lyle Kirman
consultant - Cleveland Heights, Ohio
January 8, 2011