Posted by KingC: also Kirock, am I to assume you mean de-ionized water when you say DI? I have always heard that DW and DI have pretty much the same conductivity levels? is this not true? I am curious as to what would make DI better than DW? and also, where can you buy DI water, I have never actually seen it in a store?? (you'll have to excuse my water-ignorance )
Yes that's what I mean, DI is de-ionized water, it's an industry jargon. DW (distilled water) is a much lower quality semi-DI water. DW is water that is filtered, then boiled to steam. The steam is collected and condensed back into water, just like the process of making liquor(Liquor/alcohol manufactures have the trade name of "Distillery"). The resulting water is much better in terms of ions and particulates but the process is not perfect. Alot of the ions simply evaporate with the water and of course recondense with it and therefore are still present in the finally product. The resultant conductivity is in the range of 500-700K ohms/cm.
DI water can be much higher then this (in resistivity, which is what we want).
My first experience with DI water system was in a Dialysis ward in a hospital.
I was a Dialysis Tech and we maintained all the equipment etc. That system was capable of running 20 dialysis machines simultaneously with each machine having a flow rate of 2-3L/min. The conductivity was in the range of 1-2Megaohms/cm. In the semi-conductor lab I spoke of in my previous post, the system was much smaller but capable of 18-20Mohms/cm. If the conductivity fell below 10Mohms/cm it was time to change the cartridges.
Resistance per centimeter is the standard for measuring DI water pureness.
It's literally a high impendance meter with the probes physically seperated by exactly one centimeter.
CMH:
Everyone is concerned about keeping water uncontaminated. Does anyone know why contaminated water is considered bad? Its not. Being conductive is bad.
I thought that IS what we are talking about, contamination(of whatever kind: minerals, ions, bacteria)=conductivity, which is bad. You make excellent points here about the water cooling and have the experience. It's you and KingC that are really helping jezreex, I'm just adding a little knowledge to the mix in a limited capacity.
What I was recommending is called "Pacification" and is used in chem and physics labs the world over. The process is to use the substance you WANT to system/container/object to be filled with to "clean" the system of other unwanted substances. Heating the system during the process increases the effect. Also applying negative pressure (vacuum) encourages degasing (micro pockets of air). This is based on the basic principle of particles moving from an area of high concentration to an area of low concentration.
I'm not sure about the rusting point you made CMH. I would hope the system is made from copper pipe, plastic parts and either aluminum or copper cooling block, thus rusting is negligeable. I though the real point here about water quality (DI and DW) was more of a safety/insurance thing just in case the system sprung a leak!
Finally, I'm not sure where you could buy DI water, you might be able to get some from a local hospital. Their labs would have many DI system in them. If you had a contact or just asked real real nicely they might give you a bucket.
If they do, make sure you pacifie the container with at least DW first.
Cheers.