RO/DI Corrosion?

[shesacharmer]

In the course of real life I had the opportunity yesterday to discuss RO/DI with a water expert...30 years in the business and his only job ever.

He astounded me when he told me that RO/DI water will corrode your faucet unless you ensure it is made entirely of stainless steel and it's best to use PEX (or equivelent) lines to hook it up for the same reason.

I've never seen anyone here mention this. I don't have one of these units but I'm glad that I know now before I get one that this is a concern.

 

[Randy Holmes-Farley]

The RO/DI water is ONLY downstream of the metal tap faucet. You should not have any metal parts in the RO/DI itself, and no one does.

 

[shesacharmer]

I KNEW you would have the answer Randy! Thanks!

 

[disc1]

You should not have any metal parts in the RO/DI itself, and no one does.

But if you did it could definitely be corroded. This is the reason people get so serious about there being no brass or copper downstream of the RODI.

 

[Fade2White12]

Exactly. For most people, this just is not a concern, unless you are using copper or some other common metal to transport finished DI to your tank or collection (but who would do that?).

 

[shesacharmer]

I suppose if someone is unfamiliar with the problem they might make that mistake so I hope the newbies read this.

 

[Ztrain]

Pardon my noobness but I don't get it. There would only be a problem after the RO/DI part correct? And we're collecting the DI part to go in our tanks. So will the waste water cause metal corrosion or only the DI part? Also does this create a problem when taking the water out of the tank? What about metal items in the tank such as parts in our power heads and or heaters? Also when doing water changes was planning on dumping it down the toilet will the cause corrosion?

 

[Fade2White12]

Pardon my noobness but I don't get it. There would only be a problem after the RO/DI part correct? And we're collecting the DI part to go in our tanks. So will the waste water cause metal corrosion or only the DI part? Also does this create a problem when taking the water out of the tank? What about metal items in the tank such as parts in our power heads and or heaters? Also when doing water changes was planning on dumping it down the toilet will the cause corrosion?

As a universal solvent, water stripped of most ions then becomes "hungry" to replace those ions. So deionized water (not your waste water) will react with common/poor metals like iron and copper and essentially dissolve them in order replace those bonds.

If there was no oxygen, however, DI water would not be corrosive at all, but since most circumstances wouldn't allow for completely sealed systems, this is not generally possible.

Once salt is added, it limits the corrosive nature of DI water due to the introduction of the salt itself, as well as the trace elements/metals that accompany it. Now salt water is corrosive in it's own right, and it's impact on the metals within our tank is already well noted.

 

[disc1]

Pardon my noobness but I don't get it. There would only be a problem after the RO/DI part correct? And we're collecting the DI part to go in our tanks. So will the waste water cause metal corrosion or only the DI part? Also does this create a problem when taking the water out of the tank? What about metal items in the tank such as parts in our power heads and or heaters? Also when doing water changes was planning on dumping it down the toilet will the cause corrosion?

As for the metal items in your tank they're not in RODI water, they're in salt water that you made from RODI water. It isn't ultra-pure water anymore.

When you dump it in the toilet it picks up salts and what not really quick. At that point it is no longer DI water. But you're not talking about dumping ultra-pure water, you're talking about dumping water from your tank. That's not ultra-pure RODI water, that's salt water that you made from RODI. Not the same thing at all. Once you put the salt in it isn't ultra-pure anymore. It now has salt in it.

The waste water isn't ultra-pure. It's even less pure than the tap water you started with.

This is only a problem where you are running nothing but ultra-pure water through a metal fixture. Once it is being mixed with salt or other water then it is no longer ultra-pure and there's nothing to worry about.