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DI water testing?

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#51547

DI water testing? | 24 August, 2007

I'm needing to use DI water for the first time. I called the local Culligan man and was told that distilled water was the same as DI so I bought some. I wanted to determine if it was DI so after reading the postings in the forum I determined the resistance could be an indication. Also someone said a copper penny would corode, turn green. It failed both of those tests.

I returned the distilled and paid more money for DI water. I get about the same resistance as the distilled. 300k. My tap water reads 5k.

Maybe my test method is invalid. Penny still bright after an hour +. Is this a slow reaction or just a rumor? What do I need to properly test the resistance of the water?

Thanks for your help.

Dave

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#51548

DI water testing? | 25 August, 2007

Dave,

First of all, distilled water is not DI water. It is not the same thing.

If you require DI water, you should know what quality is expected for your application. For example, for defluxing applications, generally DI water quality exceeding 2 � 3 M-Ohm is sufficient although normally the quality is about 7 � 8 M-Ohm. In semiconductor applications, 18 M-Ohm is not unusual.

As for the use of copper, its not a good idea. Metal pipes should be stainless steel, suitable non metallic materials are CPVC, polypropylene, or Teflon.

Measuring the quality of DI water can be tricky. If you are measuring DI water in an open-air environment, it may not remain �DI� for very long. DI water can absorb carbon dioxide from the air, lowering the water�s quality. In addition, if you poured the DI water into a container, it most likely absorbed some contamination. Finally, there is not a real standard whereby water can be referred to as DI. Water may be accurately referred to as DI when its resistivity is less than 1 M-Ohm all the way to 18.3 M-Ohm.

Mike Konrad Aqueous Technologies Konrad@aqueoustech.com

www.aqueoustech.com

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GSx

#51549

DI water testing? | 25 August, 2007

In addition, plenty of good news on this link.

http://en.wikipedia.org/wiki/Deionized_water

Regards........GSx

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#51552

DI water testing? | 25 August, 2007

Is it sufficent to simply put meter probes in the water to get a resistance reading?

I'm very skeptical of the Culligan man as they tried to pass distilled water for DI water. As I watched my container being filled I asked how they determined when their resin bed was expended. The answer was "we just change them after awhile." No quality control! The water was dispensed into a 6 gal. plastic container with the water dropping causing airation as it filled. Would this short exposure cause enough CO2 to mix to cause a reduction in the resistance?

I'm thinking I need to use a resin bed and process the water as I need it. Not buy processed water and try to store it. I have located disposable cartridges and that would be my best economy as a couple of months can go by between uses. Should the cartridge be drained between uses to prevent bacteria inside or does it matter?

I should add that I intend to use it for a rinse after aqueous cleaning of PCBs. I need some way to determine when it's time to change the cartridge.

Thanks, Dave

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#51562

DI water testing? | 27 August, 2007

Q1: Is it sufficent to simply put meter probes in the water to get a resistance reading? A1: No. You need a meter for the purpose. Myron-L [myronl.com] is one such company

Q2: I'm very skeptical of the Culligan man as they tried to pass distilled water for DI water. A2: Distilling water is a method of deionizing water. For some purposes DI and distilled water are identical. For others, they are not. If you buy distilled water, get a written certification of a conductivity of less than 1 uS-cm at the time of packing (it may rise to about 5 if not consumed rapidly).

Q3: As I watched my container being filled I asked how they determined when their resin bed was expended. The answer was "we just change them after awhile." No quality control! The water was dispensed into a 6 gal. plastic container with the water dropping causing airation as it filled. Would this short exposure cause enough CO2 to mix to cause a reduction in the resistance? A3: Sure. How well rinsed was the container?

Q4: I'm thinking I need to use a resin bed and process the water as I need it. Not buy processed water and try to store it. I have located disposable cartridges and that would be my best economy as a couple of months can go by between uses. Should the cartridge be drained between uses to prevent bacteria inside or does it matter? A4: We not familar with disposable cartridge DI systems. We're not sure resins like to do dormant.

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#51566

DI water testing? | 27 August, 2007

Dave,

I'd be skeptical too, with that response!

I've got a Culligan DI system installed here, and it's got it's own resistivity test meter. When the light goes red, it's time to call and get my resin changed. It's worked out pretty well here. Based on my experience with Culligan, I'm very surprised at your experience! Maybe it's just our local guy...

..rob

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#51571

DI water testing? | 27 August, 2007

Rob

When the little light goes red, your supplier changes your ion beds. How does he determine when to change the carbon bed? Carbon certainly won't go bad as fast as the ion beds. Right?

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#51573

DI water testing? | 27 August, 2007

I have requested info on the disposable cartridge. I was told it was made for lab use and has an indicator to show depleated use. I will try to determine how the indicator works, ie. measures quality at the outlet (hopefully) or some other scheme?

My situation is causal intermittent use for our board runs. I don't need a monthly service charge when it's not needed.

Thanks for your input.

Dave

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#51583

DI water testing? | 28 August, 2007

Dave,

To tell you the truth, I couldn't tell you. I came into this company with the system installed. When the resistivity is depleted, I call Culligan.

It may only be an in-line cartridge filter that they change. We've noted a change in water quality manifested by water spots on the boards, and reduced cleaning quality as the resistivity of the water changes. And, subsequently, reduced water spots and increased cleaning quality after Culligan services the system.

I don't produce boards for anyone that requires high-levels of ionic contamination testing; so I don't have definite reports of effectivity of this system in cleaning boards; simply our internal conjecture on the visual cleanliness of the boards after they've been through wash.

..rob

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bmaheu

#51613

DI water testing? | 30 August, 2007

#51614

DI water testing? | 30 August, 2007

Rob

If your supplier replaces your carbon bed when the ion beds require replacement [when you call after the light goes red], it will not hurt anything, except increase your costs.

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#51620

DI water testing? | 31 August, 2007

OK, I've found out more on the disposable cartridge. It is made by Siemens. There are four in the series. One of the part numbers is 3C0600002.

It has colored resin and changes color to indicate depletion. Has hose connects each end. I will try it and see how long it works for my ocassional use.

Dave

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