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topic 33660

How to improve pH for DM water

A discussion started in 2005 & continuing through 2017


Q. Here we're adding pH booster to increase DM water pH value, I want to use liquid ammonia for increase pH value for our DM (demineralized) water. already I analysed with liquor ammonia and DM water .these character also same with pH booster .now my question actually that pH booster we purchased out market I don't know that chemical composition now I want that chemical composition and reaction about liquor ammonia and DM water.please I am expecting you are answer.


Senthil Kumar D
Sterlite Industries (India) Ltd - Tuticorin, Tamilnadu, India


? I'm not sure if I understand your question, Senthil. Am I right that you are presently using a proprietary "pH booster" and you are pretty sure it is based on ammonium hydroxide--but you tried straight liquid ammonia and it did not work as well? So now you want to know what other ingredients are in the trade secret formula that you purchased?

Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey


A. I have a question as well. When you say "improve" the pH, what pH value are you trying to reach? Measuring the pH of ultra pure water can be tricky. You may want to purchase a pH meter designed for that application. Also, your DM water will probably have a pH below 7.0 anyway.

Joseph Lockrem
- Indianapolis, Indiana, USA


A. Dear Sir,
As there are many other ways to correct the pH or to get the desired level of pH of final product water coming out to DM plant. What is the exact system you are using at the moment and how it is working at what efficiency?

Aniruddh Gupta
- New Delhi, Delhi, India


Q. What is the relation between pH and conductivity of service water. I would like to maintain the pH between 5.5 to 8 using very cost effective method for a particular application, Please recommend the methods.

krishnan [last name deleted for privacy by Editor]
engineer - Singapore


A. There is no dependable relationship between conductivity and pH, Krishnan. Seawater is hundreds of times as conductive as rainwater of the same pH.

Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

May 31, 2009

Q. I am Arunachalam - Finishing engineer in a reputed concern. We are processing EN31 material through tumbling.

Requirement: Gloss(mirror finish)during tumbling

Past: We have achieved the above requirement 3 months before while the DM water pH was 6.5 to 7.0.

Present: We could not achieve the mirror finish now while the DM water pH was 8.0 to 8.5.

Kindly clarify me the importance of DM water pH during tumbling.

Arunachalam M
Employee - Coimbatore, Tamilnadu, India

March 8, 2012

Q. Sir,

Firstly, would like to thank you for your answers.

We have recently commissioned DM Water unit, in our Plant. Quality of product water is quite good, except for pH
which is measuring 6.6 consistently.

My end use of the water is make up feed to boiler, where water of 7 pH or slightly above is ideal.

How can I boost the pH of the product water in a cost effective way, with minimum maintenance overheads.

YK Rao

Kameswara Rao Yendamuri
- Giridih, Jharkhand, India

October 26, 2016

Q. Dear sir
Or DM water pH was around 6; recently we noticed that the DM pH reached to 8.2. Can you advise if we have a problem or not, and what we can do to return the pH values as before?

Thanks in advance.

Khalid qasem
- Amman, Jordan

October 29, 2016

A. If the resistivity is > 1 Megohm, it is usually OK to ignore the pH. It is very difficult to accurately measure the pH of high purity water with standard pH instrumentation.

Lyle Kirman
Consultant - Cleveland Heights

November 15, 2016

A. Good day Khalid.

I too experienced difficulties with pH measurement of our R.O. water. I do not know about your system, but my problem was pH readings lower than normal.
It is problematic to measure pH of low ionic strength solutions with conventional pH electrodes.
Perhaps you might try a pH electrode which is suitable for low ionic strength solutions.
Is your electrode refillable, and are you cleaning the electrode with dilute HCl, say 1.0N?
What is the TDS of your DM water?
I increased the TDS (from 2 ppm)of the R.O. sample with NaCl to 100 ppm., and the pH measurements were returning to normal values.
My system involves a water softener, ion exchange, and ultra filtration via filter membranes. I do expect pH @ 5.5-5.8 with this system.
Perhaps you need to address all aspects of your DM system, and monitor pH values at each stage.
Hope this helps.


Eric Bogner, Lab. Tech
Aerotek Mfg. Ltd. - Whitby, Ontario, Canada

October 6, 2017

Q. We have potable water pH 5, but we want after DM for water to be 6 to 6.5. But we are not getting as wanted specification. We are getting only 5.5 to 5.7. how to increase pH of DM water

venkanna babu
- abidjan , ivory coast

October 10, 2017

A. Hello Venkanna,

You could try to heat your DM water to remove CO2 from it, it should raise the pH of your DM water to 6-6.5.

Your pH meter should be in extremely good condition to measure pH values in DM water, as it has very low concentration of any ion. Please take this into account when analysing your data and what values you should consider as reliable and what values you should discard.

Best of luck!

Daniel Montanes
TEL - N FERRARIS - Canuelas, Buenos Aires, Argentina

October 17, 2017

A. If the water has a resistivity of > 5 MegOhm, then pH is meaningless because most pH meters do not work correctly on water that is this pure.

Lyle Kirman
consultant - Cleveland, Ohio

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