RO Water Chemistry

[goodgreef]

Hello all,

I know this is a dumb question but someone once told me there is no such thing as a dumb question.

Does RO water (unsalted) chemistry change over time? In other words, Is 4 week old RO water better or worse to use in water changes than RO fresh from the spigot? I think not but I'm finding my former chemistry classes lacking with this info.


Please forgive my ignorance on this!!!


Thanks,

goodgreef

[spelodiver]

If you keep the water in a closed container then it will keep almost forever...
With RO and better yet RO/DI..all the stuff is removed that will cause the water to spoil...FWIW...IMO.

[BeakerBob]

RO water is like a sponge and RO/DI water is worse. The reason for this is that most of the elements have been artificially removed by membrane filtration and ionic exchange. This water will literally eat stainless steel up.

If you store the RO/DI water in a glass or plastic container, it will absorb gases from the air, like CO2, O2, CO, etc. until it reaches equilibrium (providing the gas is in sufficient concentration). Likewise, it will also pick up organic compounds if they are in the air, like volatilized solvents and cleaning agents. If you cap the container, the absorption will be limited.

If the storage area is relatively free of such organic compounds and gases, the water should be OK to use for a number of months. You can certainly use fresh RO/DI water, but it is lacking in oxygen.

[ReeferRob]

RO water is like a sponge and RO/DI water is worse. The reason for this is that most of the elements have been artificially removed by membrane filtration and ionic exchange. This water will literally eat stainless steel up.

If you store the RO/DI water in a glass or plastic container, it will absorb gases from the air, like CO2, O2, CO, etc. until it reaches equilibrium (providing the gas is in sufficient concentration). Likewise, it will also pick up organic compounds if they are in the air, like volatilized solvents and cleaning agents. If you cap the container, the absorption will be limited.

If the storage area is relatively free of such organic compounds and gases, the water should be OK to use for a number of months. You can certainly use fresh RO/DI water, but it is lacking in oxygen.

Great info Bob! So it probably is not a good idea that I keep my 55 gallon barrel in the laundry room with the lid off and unsealed huh?

[cephalotus]

+1 on what Beaker Bob said, and your not supposed to drink RO water that has not been refridgerated after 24 hours.

[Bella127]

What would be better, glass or plastic container? I use the old brute can w lid , ( I have no phosphate issues at the moment due to leaching phosphates from the storage can) but that is another subject

[BeakerBob]

I store most of my DI water in sealed 5 gallon plastic jugs and keep about 20 gallons in a plastic Rubbermaid trash container in the basement for immediate use (within a period of about 3 weeks). I don't use a lot of solvents, pesticides or cleaning agents in the area, but I do notice that it picks up various odors.

[AZDesertRat]

The amount of contaminants RO or RO/DI will pick up is dependent on your cleanliness and housekeeping, even with open containers. Yes RO/DI is very agressive, it is wanting to get back to its normal "dirty" state so attracts anything it can from the container walls or the air but it has its limits. My 23 gallon Rubbermaid Recycling can is used as my autotopoff storage, it has a loose fitting lid and sits in the garage which also doubles as a laundry room and workshop. I tested the TDS straight from the RO/DI and its 0 then from the storage container and its only 2. The container has been in use over two years and has never once been drained or cleaned.
I am careful though about things like pesticides and woodworking with lots of dust in that area, just use common sense.

[BeakerBob]

TDS (Total Dissolved Solids) is a good way to measure the purity of the water in terms of "dissolved" solids as well as ionic and elemental salts (ie. sodium, chloride, nitrates, phosphates, magnesium, sugar, dirt, etc.).

Just be careful not to rely on the TDS meter to tell you if the water has absorbed any BTEX compounds (Benzene, Toluene, Ethyl Benzene or Xylene compounds found in gasoline) or other organic solvents, pesticides, ammonia or herbicides as it will not show up on a TDS meter.

[goodgreef]

Thanks a bunch reef types. Great info!!! I guess It's safe to put RO in a covered plastic container for a week or two. I will put a air hose in the water prior to using for oxygen.


goodgreef