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When to recharge mixed bed in DM water plant


Q. We have a DM plant with capacity of 400 liter/hour which is running 24 hours a day. This plant is filling water into a tank with 1000 liter capacity. We are maintaining water conductivity below 0.3 micro Siemens. If at the end of the day the conductivity increases to 1 micro Siemens, what should be the plant capacity to bring it below 0.3 micro Siemens?In our system we are using copper, SS and breaded PVC pipes. The 7.5 HP pump is used for circulating the water from storage tank. The pump capacity is 480 liter/minute. The small pumps with 400 liter/hour capacity are used for re-circulating water through mix bed units. The storage tank is air-tight. We are not using nitrogen filling. The temperature is around 35-40° C during the operation as the DM water is used for cooling copper heatsinks.

I want to know when I should recharge the mixed bed unit. What is the formula for recharging the mix bed unit with respect to the conductivity of the water?

Ahmed Syed
Engineer - Gandhinagar, Gujarat, INDIA


A. Your problem is not clearly explained. When you say "recharge", do you mean you have an exchange tanks as DI mixed beds? Where is the 480 l/m pump recirculating water to -- from the storage tank to the copper sinks? Why is 1 microsiemen not good enough? The application should not require much better purity. Your materials and no nitrogen blanket will allow CO2 from the air to mix with the water even though the tank is air tight as you say.
If CO2 is the contaminant, to go from 0.3 microsiemens to 1 microsiemens will take approximately 100 cubic meters of recirculated water per liter of mixed bed resin.
I hope this helps.

Juzer Jangbarwala
- Brea, California, USA


Q. We are using this DM water plant for water cooled heatsink. The total system is like this. A multi-secondary transformer is supplying AC power to the 80 units. Each unit is connected in series. Each unit is converting 940 VAC in to 100 to 1000 VDC(variable). All secondary of the transformer is isolated from one another and from ground. The first unit is at 1000 VDC from earth, Second unit is at 2000 VDC from earth and so on. The Electronics parts are mounted on the heatsinks in each of the 80 modules. All the modules cooling water is supplied from one plant, which gets short circuited after some distance. The flow is from storage tank to one supply header with 80 branches and back to return header and to storage tank. To avoid electrical short circuit between two modules we require very low conductivity water. We are using water because it is excellent coolant. We are using stored water in the tank at 480 l/m to circulate in this main loop.

The water purification loop is from storage tank to mix bed unit and back to storage tank at 400 l/h rate. For this system we need to know the capacity of the mix bed plant to achieve 0.3 micro siemens conductivity with 37 to 40 ° ambient temperature.

I mean recharging of mixed bed unit. When should I recharge resins of mix bed unit with acid and caustic? What is the formula after which time one should recharge the unit?

Ahmed Syed
- Gandhinagar, Gujarat, INDIA


Q. Want technical know-how on DM water plant.

Jasbir Singh
new enterprenuer - Delhi, India


Hello Jasbir. Sorry, but it isn't clear what you want. Do you want us to recommend books about DM, or are you seeking a DM Water consultant? Please give some clues about what general type of DM system you are looking into -- what is the water used for, what is the source of the water, what is the flow rate? Thanks!

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


Q. Please, we want to know how to check DM Water by simple method.
We purchased a DM Water for our paint line.

Dilip Gupta
shock absorber mfgr. - Indore, Madhya Pradesh, India

A. Hi, Dilip.

Simplest is just a conductivity meter in the pipeline. Your DM system vendor will have them. Good luck.


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


Q. Dear Sir,

Does the quality of DM water deteriorate upon storage (with caustic breather at vent and water jacketing of overflow) for more than some specified period? If yes, what is that period?

S. Banerjee
- Jamshedpur

March 28, 2009



July 6, 2010

Q. I want an e-book describing water chemistry as applicable to power plant industry.

Ramalingam R A
engineer - Bikaner, Rajasthan,&India

Ion Exchange Materials

September 28, 2010

Q. Could you please recommend a few books on DM water plants? I would not be interested in being in touch with DM plant vendors presently. A few recommendations on quality books on this side, would be highly appreciated.

Thanks and regards,


Keshav [last name deleted for privacy by Editor]
- Bangalore, Karnataka, India

Caustic breather / CO2 breather in DM storage tank

March 31, 2012

Q. We have 2 DM Tanks with each storage capacity 500 M3. The pH of DM Water is 6.0, while it should be 6.8 - 7.2, so we want to use caustic breather to absorb CO2.
Can anyone tell me about caustic breather function, and its supplier?
Please help us.

Ashish Garg
- Bhilai, Chhattisgarh, India

June 6, 2014

Q. What is the cross-sectional diagram of CO2 Breather and how does it work? What is the quantity of KOH to be filled in the CO2 Breather?

Naseem Javed
Employee - India

pH of DI water in storage tank rises overnight

July 13, 2014

Q. In evening when we check pH of storage tank it is 6.0; but in morning we check and found pH automatically rises to 7.2 in same storage tank. I can't understand what is happening?

Some told me it is due to use of caustic for charging of mix bed? Please suggest something to overcome this issue.

nidhi sharma
- chandigarh india

Ed. note -- Readers: If you have sufficient knowledge to pose a cogent question, you probably have sufficient knowledge to answer one of the unanswered questions which precedes your own!
A long string of unanswered questions leads to nothing but ever more unanswered questions, and the death of the thread. Perhaps because readers tell themselves "I'm happy to try to help people, but not to perpetuate and enable the ways of the selfish ones who always want help without ever taking the time to help anyone else" :-)

Urgently need to know about regeneration of cation, anion, mixed beds and regenerant preparation

October 24, 2016

Hi this is amit.
I want to know about regeneration of all three beds, i.e., cation bed, anion bed, and mix bed of DM water plant.
And also want to know about the solution preparation for regeneration of the all beds.

It's urgent.

Amit kumar
lab - Dehradun uttrakhand india

October 2016

A 'highly specific question' can probably be defined as one where the answer we seek has fewer words than the question :-)

A. Hi Amit. Since it's urgent, please immediately retain a water quality consultant to train you. Or maybe the system supplier can send in an applications engineer to advise and train you? Although people can probably recommend good books you can read on the subject, that won't solve an urgent problem. Readers can probably answer highly specific questions for you though. Good luck.


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

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